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Sail Drive Corrosion


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#1 ColinD

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Posted 02 May 2008 - 09:25 PM

I have a year old Yanmar 2YM15 Engine and SD20 Saildrive and after 6 months sailing in Lake Ontario the Saildrive and Prop exhibit corrosion. White (bubbles) and (flaking) on Drive and Prop despite protective Zinc Anode. Is this Copper (VC 17 Antifouling) and Aluminum galvanic action? Bad paining on both? Made in China? Lake Ontario is a Giant Battery?
What corrective actions are there? Note that above the Rubber Skirt the corrosion is not there.

#2 New Morning

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Posted 02 May 2008 - 09:40 PM

Assuming you didn't put bottom paint on the saildrive, then the proximity of the bottom paint should not be a problem.

I've had a Volvo saildrive on SF bay for almost 8 years with no problems. I change the zinc as it wears away (usually about every six months) and don't do anything to the aluminum drive strut. The paint on the saildrive has bubbled and flaked a bit, but nothing extraordinary.

Attached is a photo taken after about 2 1/2 years that you can compare to what you're seeing.

Attached File  DSC_0466.JPG   127.22K   113 downloads

#3 familysailor

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Posted 02 May 2008 - 10:37 PM

Two things---
You should probably have a sacrificial anode other than zinc in fresh water. I think it's magnesium. Check with Yanmar and Saildrive.

Also check to see if your boatbuilder grounded your saildrive. Mine was--- in spite of the red circle with diagonal red slash on a tag attached to the drive unit. The owners manual also specifically said not to ground the drive unit. The unit was also grounded through the throttle/transmission linkage due to a missing series of teflon bushings/washers. Corrosion was happening in spite of the zincs. (we are in salt water)
Had a little shitfight with the dealer and builder, but they eventualy paid for the cost of tracing the ground circuts and isolating the drive per Volvo's instructions.

#4 Hitchhiker

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Posted 03 May 2008 - 12:13 AM

It's the copper in the paint. You absolutely should not paint the saildrive with any copper based paint. There are aluminum compatible bottom paints, do a google search and you should find good product.

#5 justsomeguy

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Posted 03 May 2008 - 12:20 AM

I have a year old Yanmar 2YM15 Engine and SD20 Saildrive and after 6 months sailing in Lake Ontario the Saildrive and Prop exhibit corrosion. White (bubbles) and (flaking) on Drive and Prop despite protective Zinc Anode. Is this Copper (VC 17 Antifouling) and Aluminum galvanic action? Bad paining on both? Made in China? Lake Ontario is a Giant Battery?
What corrective actions are there? Note that above the Rubber Skirt the corrosion is not there.


I make my (Lake Ontario) zincs shiny every year. Clean off the old crap that's already reacted because it's not protecting you anymore. This year I'm going to Magnesium. The long and short of it is that my 4 year old saildrive looks brand new due to the maintenance each haul out.

#6 v-max

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Posted 05 May 2008 - 12:15 AM

I had this problem on a boat I recently purchased. After much research here's what I found.

1) In fresh water you must use magnesium anodes.

2) In fresh water you will not need to put ablative paint on the saildrive but in salt water you should use a product like Trilux II for protection.

3) a previous post mentioned checking your ground, good idea! Also leaving your boat plugged into shore power continuously may not be a good idea, especially if this problem persists. In fact in may not have been your boat at all, it may have been a boat parked beside you radiating all the electricity into the water causing your corrosion because you didn't have magnesium anodes.

Hope this helps..

#7 dacapo

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Posted 05 May 2008 - 03:45 PM

is the boat in a marina?? or mooring. May be a stray current from someone elses boat.

#8 ColinD

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Posted 06 May 2008 - 02:49 PM

Assuming you didn't put bottom paint on the saildrive, then the proximity of the bottom paint should not be a problem.

I've had a Volvo saildrive on SF bay for almost 8 years with no problems. I change the zinc as it wears away (usually about every six months) and don't do anything to the aluminum drive strut. The paint on the saildrive has bubbled and flaked a bit, but nothing extraordinary.

Attached is a photo taken after about 2 1/2 years that you can compare to what you're seeing.

Attached File  DSC_0466.JPG   127.22K   113 downloads
No bottom Paint on Saildrive or Prop. Mine is 5 times worse.



#9 ColinD

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Posted 06 May 2008 - 02:51 PM

Two things---
You should probably have a sacrificial anode other than zinc in fresh water. I think it's magnesium. Check with Yanmar and Saildrive.

Also check to see if your boatbuilder grounded your saildrive. Mine was--- in spite of the red circle with diagonal red slash on a tag attached to the drive unit. The owners manual also specifically said not to ground the drive unit. The unit was also grounded through the throttle/transmission linkage due to a missing series of teflon bushings/washers. Corrosion was happening in spite of the zincs. (we are in salt water)
Had a little shitfight with the dealer and builder, but they eventualy paid for the cost of tracing the ground circuts and isolating the drive per Volvo's instructions.


Yanmar have supplied a free Magnesium Anode Vs Zinc original.



#10 ColinD

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Posted 06 May 2008 - 02:52 PM

My problem is Yanmar Drive and Prop.

#11 W A F I

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Posted 06 May 2008 - 04:12 PM

Hi,

I worked for Mackboring and Yanmar for 10 years and we had a problem with this in fresh water. I studdied corrosion on the tartan POSes.

Number one! YOU NEED A MAGNESIUM ANODE!!! zinc does not work in frsh water. Contact me and I can sell you one or go to BOATZINCS.COM and buy one.

number 2. Make sure your unit is NOT GROUNDED with the rest of the boats grounds this in a no no because your drive is like an anod in fresh water. Alluminum will act as an anode in fresh water so any electrolisis you may get will attack the alluminum leg first if the anode on it is made of zinc. IN FRESH WATER

The sail drive is grounded dirrectly to the battery VIA the engine ground cable. Your battery ground acts as a sponge soaking up all stray current. By grounding your drive to the boats stray ground cable you are introducing all kinds of of iterference to the direct engine ground. YOUR ENGINE IS NOT A GROUND BAR DO NOT USE IT AS ONE!!!!! YOU HAVE A GROUND BAR FOR THAT.

Number 3 make sure the hose that connects the raw water pump to the sail drive water valve is NON WIRE BOUND hose. this can bind dissimular metals together and speed up a corrosion.

Number 4 make sure the paint on the drive leg is intact and not scratch exposing raw alluminum to the water if there are than repair the finsh. I recomend an epoxy type of coating you can even use a fairing compound to do this.


Hope this helps. If you have questions you can call me at 262-770-1159. If I don't answer leave me a message and I will call you back.


I had this problem on a boat I recently purchased. After much research here's what I found.

1) In fresh water you must use magnesium anodes.

2) In fresh water you will not need to put ablative paint on the saildrive but in salt water you should use a product like Trilux II for protection.

3) a previous post mentioned checking your ground, good idea! Also leaving your boat plugged into shore power continuously may not be a good idea, especially if this problem persists. In fact in may not have been your boat at all, it may have been a boat parked beside you radiating all the electricity into the water causing your corrosion because you didn't have magnesium anodes.

Hope this helps..



#12 DEAD MONEY

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Posted 09 May 2008 - 01:36 PM

Hi,

I worked for Mackboring and Yanmar for 10 years and we had a problem with this in fresh water. I studdied corrosion on the tartan POSes.

Number one! YOU NEED A MAGNESIUM ANODE!!! zinc does not work in frsh water. Contact me and I can sell you one or go to BOATZINCS.COM and buy one.

number 2. Make sure your unit is NOT GROUNDED with the rest of the boats grounds this in a no no because your drive is like an anod in fresh water. Alluminum will act as an anode in fresh water so any electrolisis you may get will attack the alluminum leg first if the anode on it is made of zinc. IN FRESH WATER

The sail drive is grounded dirrectly to the battery VIA the engine ground cable. Your battery ground acts as a sponge soaking up all stray current. By grounding your drive to the boats stray ground cable you are introducing all kinds of of iterference to the direct engine ground. YOUR ENGINE IS NOT A GROUND BAR DO NOT USE IT AS ONE!!!!! YOU HAVE A GROUND BAR FOR THAT.

Number 3 make sure the hose that connects the raw water pump to the sail drive water valve is NON WIRE BOUND hose. this can bind dissimular metals together and speed up a corrosion.

Number 4 make sure the paint on the drive leg is intact and not scratch exposing raw alluminum to the water if there are than repair the finsh. I recomend an epoxy type of coating you can even use a fairing compound to do this.
Hope this helps. If you have questions you can call me at 262-770-1159. If I don't answer leave me a message and I will call you back.


and where were you when I had my Sail Drive disintergrate from corrostion...LoL

All sounds VERY good info.......but I also think someone close to him is sending out stray electricity.

#13 W A F I

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Posted 12 May 2008 - 02:56 PM

and where were you when I had my Sail Drive disintergrate from corrostion...LoL

All sounds VERY good info.......but I also think someone close to him is sending out stray electricity.



LMAO.... I was in chicago trying to figure this out in lake michigan since no body in the company new what cold weather or fresh water is.

some one is sending out stray current I am sure of it. Probably the wires on the dock supplieg power. I have seen power come from all over and all kinds of sources. but there are ways to combat this prob.

#14 luckyjim

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Posted 03 July 2008 - 03:30 AM

I have a year old Yanmar 2YM15 Engine and SD20 Saildrive and after 6 months sailing in Lake Ontario the Saildrive and Prop exhibit corrosion. White (bubbles) and (flaking) on Drive and Prop despite protective Zinc Anode. Is this Copper (VC 17 Antifouling) and Aluminum galvanic action? Bad paining on both? Made in China? Lake Ontario is a Giant Battery?
What corrective actions are there? Note that above the Rubber Skirt the corrosion is not there.


Read the ABYC standards - Section E-2 - and make your boat fully 100% compliant. Do all you need to do to drive up your hull potential to equal or greater than what it states in the specs. Target is -0.984 mV using an AG/AGCL reference cell according to some and greater than that according to some at the top in ABYC on this topic. Also, a few years back Yanmar started to get the picture on magnesium vs zinc. (Through people just like you!). They now offer magnesium. Use that for freshwater as others have stated here. Yanmar's SD castings (for the SD50 at least) are made in Italy by Selva S.p.A. to Yanmar specs. Still not sure about this? Contact Ward Electric in FL. They are Yanmar's experts in corrosion failures and produced some great reports on this in recent years.

LJ

#15 Sailabout

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Posted 07 July 2008 - 02:55 AM

How do you isolate the saildrive when it is bolted onto the engine that is connected to the battery negative/ground?

#16 Asymptote

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Posted 07 July 2008 - 04:22 AM

On our boat, we have non-copper based bottom paint for at least a foot radius around the saildrive unit apparently to keep stray currents away from the unit.

Since Mick Cookson did it that way, and we have had minimal corrosion in six years (salt sater/zinc anode faithfully changed), we see non reason to change.

#17 SKYDRAGON

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Posted 07 July 2008 - 12:55 PM

Any follow up on this ? Has anyone heard from B ? I called them last week and they are going to get back to me ? How was the saildrive isolated ? If you remove the grounding wire from the saildrive where is it reattached ?

#18 MoeAlfa

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Posted 07 July 2008 - 01:00 PM

How do you isolate the saildrive when it is bolted onto the engine that is connected to the battery negative/ground?

Dielectric gasket and drivetrain piece. My multimeter tells me it works.

#19 Sailabout

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Posted 07 July 2008 - 02:01 PM

Dielectric gasket and drivetrain piece. My multimeter tells me it works.

whow..I learnt something today.
Are those parts in the parts manual?

#20 MoeAlfa

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Posted 07 July 2008 - 02:24 PM

whow..I learnt something today.
Are those parts in the parts manual?

Mine's a Volvo and I'm pretty sure I've seen the parts on some diagram, but it doesn't seem to be in my files.

#21 cinnr

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Posted 08 July 2008 - 06:11 AM

Interesting to learn about magnesium vs. zinc for fresh water. Thanks for that.

Q: what's best for a boat that spends most time in fresh water, but ventures into salt water for up to 3 months at a time. Magnesium? Or is there a problem with magnesium in salt water?

#22 MoeAlfa

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Posted 08 July 2008 - 11:42 AM

Interesting to learn about magnesium vs. zinc for fresh water. Thanks for that.

Q: what's best for a boat that spends most time in fresh water, but ventures into salt water for up to 3 months at a time. Magnesium? Or is there a problem with magnesium in salt water?

The problem with Mg in salt water is that it is too reactive and, while it will protect an aluminum saildrive as effectively as Zn while it lasts, it will break down too quickly. I'm no expert, but I'd probably leave the Mg anode on, just check it often and have a spare on hand when the boat is in salt water.

#23 NonSequitur

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Posted 09 July 2008 - 08:58 AM

Interesting to learn about magnesium vs. zinc for fresh water. Thanks for that.

Q: what's best for a boat that spends most time in fresh water, but ventures into salt water for up to 3 months at a time. Magnesium? Or is there a problem with magnesium in salt water?


Find some local diver you know who does good work, and when the boat goes out for its 3mo. saltwater venture, put on a zinc. When the boat goes back into fresh, have said diver put a magnesium on. They would probably need to be done anyway.
NS

#24 SKYDRAGON

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Posted 09 July 2008 - 03:37 PM

Just spoke to Beneteau - they told me that this issue was worked out with Volvo during the design process. Evidently the engine and saildrive are isolated from each other by some type of gasket and that the negative lead in grounded to the engine. It still appears there is a ground wire on the saildrive though - wondering what this is ?

#25 MoeAlfa

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Posted 09 July 2008 - 09:50 PM

Just spoke to Beneteau - they told me that this issue was worked out with Volvo during the design process. Evidently the engine and saildrive are isolated from each other by some type of gasket and that the negative lead in grounded to the engine. It still appears there is a ground wire on the saildrive though - wondering what this is ?

If it's grounded, it's not isolated.

#26 luckyjim

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Posted 10 July 2008 - 03:44 AM

Just spoke to Beneteau - they told me that this issue was worked out with Volvo during the design process. Evidently the engine and saildrive are isolated from each other by some type of gasket and that the negative lead in grounded to the engine. It still appears there is a ground wire on the saildrive though - wondering what this is ?


...and the Volvo design of having an 'isolated' metal drive leg seems to be in conflict with current ABYC Section E-2 specifications. This is a major topic of discussion inside ABYC leadership/committees. It is not helped by the dockage infrastructure differences between the US and the other markets that Volvo sell in to in Europe. Watch for news on that relating to Ground Fault devices and the possible rewiring of the docks in the US. This is perhaps a red-herring when analysis indicates the core of the problem is that boats are being designed, incorrectly engineered (if engineered at all) and sold 'under-protected'. New boats are being delivered with hull potential values that are far lower than they need to be to protect the aluminum sail drive and with very few in compliance with ABYC Section E-2.

Further, at least one European yacht manufacturer, Bavaria, that uses 'isolated' Volvo drives delivers their product with a bonded system and an external hull zinc. Why is that? What is it that they have engineered (emphasis on engineered) that lead them to add additional hull zincs to support all the systems as part of their product?

Why do Beneteau, J-Boats, Novis and other US built boats using sail drives have significant cases of drive legs corroding out? To what extent are domestic manufacturers learning as they go and to what extent have the sail drive manufacturers knowingly or unknowingly omitted key engineering data from the yacht manufacturer and the end user?

#27 familysailor

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Posted 10 July 2008 - 04:19 PM

...and the Volvo design of having an 'isolated' metal drive leg seems to be in conflict with current ABYC Section E-2 specifications. This is a major topic of discussion inside ABYC leadership/committees. It is not helped by the dockage infrastructure differences between the US and the other markets that Volvo sell in to in Europe. Watch for news on that relating to Ground Fault devices and the possible rewiring of the docks in the US. This is perhaps a red-herring when analysis indicates the core of the problem is that boats are being designed, incorrectly engineered (if engineered at all) and sold 'under-protected'. New boats are being delivered with hull potential values that are far lower than they need to be to protect the aluminum sail drive and with very few in compliance with ABYC Section E-2.

Further, at least one European yacht manufacturer, Bavaria, that uses 'isolated' Volvo drives delivers their product with a bonded system and an external hull zinc. Why is that? What is it that they have engineered (emphasis on engineered) that lead them to add additional hull zincs to support all the systems as part of their product?

Why do Beneteau, J-Boats, Novis and other US built boats using sail drives have significant cases of drive legs corroding out? To what extent are domestic manufacturers learning as they go and to what extent have the sail drive manufacturers knowingly or unknowingly omitted key engineering data from the yacht manufacturer and the end user?



So-------

Isolate the drive, or not?

#28 SKYDRAGON

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Posted 10 July 2008 - 05:35 PM

Attached File  Engine_Sail_Drive_Bonding.jpg   74.95K   56 downloads
Here is a picture of the engine/saildrive - as you can see in the picture at right, there appears to be some sort of gasket (circled) that isolates the "front" of the engine from a "plate" at the back of the engine. The sail drive is attached to this back plate. The grounding wires are attached to the back plate which is attached to the saildrive (picture at left) - cant tell if the saildrive is isolated from the plate or not ? Dont know if this is the problem. It appears to me if the ground is attached to the plate, and the plate to the saildrive, then the saildrive is not isolated !?

#29 luckyjim

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Posted 10 July 2008 - 06:39 PM

So-------

Isolate the drive, or not?


Contact Volvo and the ABYC and ask them. Get a response in writing. Also check your Volvo warranty and owners manual. Ask a certified ABYC galvanic corrosion expert and get their sign-off.

#30 MoeAlfa

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Posted 10 July 2008 - 06:52 PM

Attached File  Engine_Sail_Drive_Bonding.jpg   74.95K   56 downloads
Here is a picture of the engine/saildrive - as you can see in the picture at right, there appears to be some sort of gasket (circled) that isolates the "front" of the engine from a "plate" at the back of the engine. The sail drive is attached to this back plate. The grounding wires are attached to the back plate which is attached to the saildrive (picture at left) - cant tell if the saildrive is isolated from the plate or not ? Dont know if this is the problem. It appears to me if the ground is attached to the plate, and the plate to the saildrive, then the saildrive is not isolated !?

The engine is painted green and the drive housing is silver. There are gaskets at all the joints. That ground is on the engine. If you're ever curious about what's in continuity with what stick a multimeter, in continuity test mode, or a simple circuit tester on the parts and and find out. A cheap multimeter is pretty basic equipment for a boat like that.

#31 Sailabout

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Posted 14 July 2008 - 06:41 AM

Attached File  Engine_Sail_Drive_Bonding.jpg   74.95K   56 downloads
Here is a picture of the engine/saildrive - as you can see in the picture at right, there appears to be some sort of gasket (circled) that isolates the "front" of the engine from a "plate" at the back of the engine. The sail drive is attached to this back plate. The grounding wires are attached to the back plate which is attached to the saildrive (picture at left) - cant tell if the saildrive is isolated from the plate or not ? Dont know if this is the problem. It appears to me if the ground is attached to the plate, and the plate to the saildrive, then the saildrive is not isolated !?

I assume the bell housing bolts are also islolated and the shift cable?
The drive shaft coupling if rubber style is easy to isolate

#32 inquiring Mind

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Posted 14 July 2008 - 07:27 AM

Attached File  Engine_Sail_Drive_Bonding.jpg   74.95K   56 downloads
Here is a picture of the engine/saildrive - as you can see in the picture at right, there appears to be some sort of gasket (circled) that isolates the "front" of the engine from a "plate" at the back of the engine. The sail drive is attached to this back plate. The grounding wires are attached to the back plate which is attached to the saildrive (picture at left) - cant tell if the saildrive is isolated from the plate or not ? Dont know if this is the problem. It appears to me if the ground is attached to the plate, and the plate to the saildrive, then the saildrive is not isolated !?


My guess would be that someone (possibly a previous owner?) added the ground wire that is attached to the sail drive. It needs to be removed and and instead attached to the engine block. It's not impossible that it was added erroneously by Beneteau in the factory, but Beneteau has (or had) people who know better. My Volvo owners manual has very specific warnings about retaining the isolation of the sail drive from the engine. As far as the shifter mechanism, it too is (or should be) isolated from the DC ground. Typically it is just mounted to the fiberglas hull and does not come in contact with any electrically grounded items. Anyone owning a Volvo sail drive needs to be aware of the isolation requirement, and insure that the isolation is maintained to prevent sail drive corrosion. I'm not familiar with Yanmar's design in this area, but I was under the impression that they are similar to Volvo.

#33 the truth.

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Posted 14 July 2008 - 08:08 AM

An defo lose that copper paint, some saildrive legs have no warranty when copper paint is applied, there is a good reason that the powerboat community use non copper applications such as International Veridian on thier outdrive legs...

#34 Nojonareach

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Posted 14 July 2008 - 11:37 AM

My problem is Yanmar Drive and Prop.


Nah your problem is either you, the dealer who sold the boat or the person who instructed zinc in fresh water. Zinc anodes in fresh water dont work and never put copper antifouling on alloy s-drives.

#35 luckyjim

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Posted 14 July 2008 - 02:35 PM

I'm not familiar with Yanmar's design in this area, but I was under the impression that they are similar to Volvo.


The design of the Yanmar SD20/SD40/SD50 range of sail drives is very different to the Volvo 'isolated' drives. The owner's manuals documentation is also very different with Volvo. The Volvo documents you can pull from the web go in to quite some detail on sail drive preparation and coating as well as the need for ensuring electrical isolation of the components. No such documents exist from Yanmar nor will they provide any details upon request in recent months. If anyone did get detailed written instructions during the last 4 years on how they should coat the drive with anti-foul from Yanmar Marine or any of their distributors (Mastry, Laborde or Mack Boring Parts Company), please email via PM with what you received in writing. Thanks, it would be much appreciated.

#36 SKYDRAGON

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Posted 04 August 2008 - 03:15 PM

Here's the response from Volvo:

The engine and saildrive should be electrically isolated from each other for the most effective corrosion protection. On the 2030 engine package this is accomplished by a series of plastic washers, gaskets and sleeves. In particular, the flywheel cover plate ( which you identify as the "back" plate) is isolated by the following: 1. Inside the flywheel housing the pilot on the back plate is isolated from the flywheel housing by a plastic sleeve which you can't see 2. The flat side of the "back plate' is isolated from the flywheel housing by the plastic gasket which you point out in your photo. 3. The bolts which hold the "back plate" to the flywheel housing go thru oversize holes in the plate, and some of the bolts travel thru plastic sleeves which center the bolts in the hole so that the bolts will not touch the side of the hole. 4. Under the head of the attachment bolt is a heavy washer and another plastic gasket which isolates the washer from the "back plate". 5. The attachment hardware for the throttle cable is designed to isolate the cable from the engine. This prevents continuity between the saildrive and engine by way of the shift and throttle cables. Theoretically, the green bonding wires that are seen in the photo should not cause any problem, but because there is the chance that they could have compromised one of the plastic gaskets, I suggest moving them from the flywheel housing to the engine block. Then examine the washers carefully for any defects. Temporarily remove the water feed hose between the engine and the saildrive and use a multimeter to measure the resistance between the the saildrive and engine. You should have somewhere around 100 K ohms of resistance. If the resistance is not there it might be good to start and check things out. Remember to close the water valve on the sail drive before pulling the hose off. Also remember, isolation or no isolation, the most effective corrosion protection comes from maintaining the anodes on the sail drive and propeller. If your boat is in salt water, use zinc anodes and if its in fresh water, use magnesium anodes."

#37 v-max

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Posted 06 August 2008 - 11:42 AM

Another Saildrive owner and I were talking about all this the other day. He raiseda great point. What about the inside of the saildrive? We've all focussed on external corrosion but what about all the internal parts? (We're both saltwater)

Someone suggested to him blocking off the intake to the saildrive and putting in another through hull for water intake to the engine. This would seal off the saildrive entirely eliminating waterflow through it.

#38 MoeAlfa

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Posted 06 August 2008 - 05:02 PM

Another Saildrive owner and I were talking about all this the other day. He raiseda great point. What about the inside of the saildrive? We've all focussed on external corrosion but what about all the internal parts? (We're both saltwater)

Someone suggested to him blocking off the intake to the saildrive and putting in another through hull for water intake to the engine. This would seal off the saildrive entirely eliminating waterflow through it.

I'm pretty sure I have seen this suggested here a couple of years ago. Someone raised the issue of gear cooling, but others didn't buy it. Some didn't like the idea of another hole in the hull.

#39 inquiring Mind

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Posted 06 August 2008 - 08:19 PM

Another Saildrive owner and I were talking about all this the other day. He raiseda great point. What about the inside of the saildrive? We've all focussed on external corrosion but what about all the internal parts? (We're both saltwater)

Someone suggested to him blocking off the intake to the saildrive and putting in another through hull for water intake to the engine. This would seal off the saildrive entirely eliminating waterflow through it.


The zincs provide corrosion protection equally to the internal coolant passages. If you are talking about the gear box internals, they are likewise protected by the zincs, and additionally are bathed in oil. I have always been concerned, however, with the possibility that marine growth might invade the internal coolant passages since there is no antifouling.




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