Impeller Life

[IStream]

So my Yanmar 4JH3-HTE engine has a recommended impeller replacement interval of 4 years or 1000 hours. Seems crazy long but given how hard it is to get to the impeller, that's fine with me.

I changed it for the first time in 2015, after I'd had the boat for a couple of years. My PO told he'd done it shortly before I got the boat but I was nervous about letting it go more than a couple of years. It looked...Perfect. So I decided to let it go the recommended interval.

Today, I pulled that impeller out after 5 years and ~250 engine hours and it looked...Perfect. No cracks, no missing corners, no apparent wear, just a slight loss of flexibility.

I guess I'm feeling a little more comfortable about the 4 year interval. Is this what others see too?

 

[Mid]

given how hard it is to get to the impeller,

change it when ever you are near it

 

[El Borracho]

They generally look good until they suddenly do not. No way would I go past 4 years or 1000 hours. That sounds like an exceptionally long time. I used to change mine with each oil change. But it ran at crankshaft speed vs. the more usual camshaft speed. Many things need renewal at 1000 hours, no?

 

[Zonker]

It's hours of use (flexing of the blades) not years. But Yanmar probably knows what they are talking about. 

 

[IStream]

It's hours of use (flexing of the blades) not years. But Yanmar probably knows what they are talking about. 

I figured that too, on both counts. The fact that it had less than 250 hours was one of the reasons I let it go (barely) 5 years. Also, to Mid's point, it's so damned hard to get to that I'm never near it for anything short of changing a motor mount.

 

[Mid]

Speedseal impellor cover and screws

 

[IStream]

I actually installed the Speedseal Life cover the first time I changed the impeller. It's got a teflon bearing and brass disc that spins with the impeller and supposedly helps keep it happy longer. Shame the company closed down, it's a nice product. However, I did find that that thumbscrews were too tight to get off by hand after 5 years. Fortunately, a 5/8" six point socket just *barely* slips over them and grabs the knurling, which lets you use a ratchet wheel to get a bit more leverage to free them up.

 

[IStream]

Unfortunately, it's not easy to reach the thumbscrews at all. Gotta swing the alternator out of the way to get to them.

When I first got the Speedseal, I chased the threads in the pump housing  and put plenty of lube on the thumbscrew threads. I think the thumbscrews are just barely too small for me to generate enough torque with two fingers pinching them in an awkward position. 

Now that I've got the 5/8" ratchet trick, it'll be easier next time.

 

[ryley]

Unfortunately, it's not easy to reach the thumbscrews at all. Gotta swing the alternator out of the way to get to them.

When I first got the Speedseal, I chased the threads in the pump housing  and put plenty of lube on the thumbscrew threads. I think the thumbscrews are just barely too small for me to generate enough torque with two fingers pinching them in an awkward position. 

Now that I've got the 5/8" ratchet trick, it'll be easier next time.

I've got that same engine and wish I'd gotten the speedseal before they went out of business. I have it on my smaller 1gm10 and it's awesome.

 

[IStream]

Fortunately, you could easily make your own for this engine. The Johnson F5B pump it uses has the o-ring slot on the pump housing side, not in the cover, so the cover itself is just a flat plate with four holes in it (that are NOT arranged in a square pattern, dammit!) 

In fact, you might be able to get away with using the existing steel cover plate with some of these thumbscrews to get 90% of the benefit of the Speedseal:

https://www.mcmaster.com/knurled-head-thumb-screws/raised-knurled-head-thumb-screws/

If the inside of the cover is scored up or the holes are too big for the shoulder of those screws, you could use it as a template for a new cover made out of 1/4" thick bronze. If you don't have access to a machine shop, you could still make a perfectly functional version with hand tools.

 

[FinnFish]

So my Yanmar 4JH3-HTE engine has a recommended impeller replacement interval of 4 years or 1000 hours. Seems crazy long but given how hard it is to get to the impeller, that's fine with me.

I changed it for the first time in 2015, after I'd had the boat for a couple of years. My PO told he'd done it shortly before I got the boat but I was nervous about letting it go more than a couple of years. It looked...Perfect. So I decided to let it go the recommended interval.

Today, I pulled that impeller out after 5 years and ~250 engine hours and it looked...Perfect. No cracks, no missing corners, no apparent wear, just a slight loss of flexibility.

I guess I'm feeling a little more comfortable about the 4 year interval. Is this what others see too?

When in the water I usually do everything in one service either 6 or 12 monthly intervals depending on how many hours the donk has done, this being primary and secondary fuel filters, oil filter and oil (every 6 months), and swap out the impeller. I have two water pumps for the donk and swap them out every 12-18 months and re-do seals and shaft etc.

Maybe a bit anal but maintenance is suppose to be preventative (don't ask me how I know that). 

 

[bridhb]

I have not replaced mine in the 4 years I have had the boat. It sat up dry for a year before I bought it and being the dumb ass I am, I have ran the engine a few times without opening the intake. It still spits water out the exhaust but I need to change it at the dock before I need to change it underway.

I have the Yanmar 2GM from the mid 1980's. It appears that I have to remove the belt driven pump to get to the face plate that is on the backside of the pump, facing the engine. Is that correct? Why they didn't put the face plate on the outside is beyond my understanding.

Is there a replacement impeller that might be "better" than the OEM one?

 

[AirisWindy]

Not a direct answer but to contribute to the discussion about preventative maintenance. Its possible that I take it too far.

I winter on the hard. From what I was taught if the boat sits for an extended period the veins, take a set in the portion of the pump where they are compressed and fail prematurely. That maybe right or wrong who knows. Once i winterize its my preference to remove the impeller for winter layup. Sometimes shit happens when im laying the boat up and that falls on the short end of the list and i just replace it. Maybe a waste of time and money but the goal is a trouble free season.

The other thing life has taught me when purchasing a new to you boat never assume that the coolant system is clear of obstructions. When i tore my motor down i found a fin lodged in a 90 degree fitting upstream from the pump.

 

[DDW]

I have used the Blue Globe impellers on my Volvo. I changed one at 5 years but it didn't really need it. Next one at 6 years but only because I was headed offshore. They claim you can run them dry for 10 minutes without ruining them.

Some people dis on them and have had trouble, but I think that was with the larger ones, not the small ones typical of sailing auxiliaries.

 

[Marty Gingras]

From what I was taught if the boat sits for an extended period the veins, take a set in the portion of the pump where they are compressed and fail prematurely.

In the '70s and '80s, impellers absolutely would take a set. Not sure about the '90s. Impellers since the '00s are much less likely to take a set.

 

[JC522]

You don't want to have to dismantle the heat exchanger to remove all the little chunks of impeller that will get lodged in there if one or more of the veins break off. I change the impeller every year during Spring commissioning.

 

[Quickstep192]

How’s that saying go? Your purpose in life may be an example to others of what not to do; something like that.

I changed my impeller last spring. I needed to move the boat to a temporary slip so I figured I’d do the impeller after I got the boat back home.

No water coming out the exhaust after starting. I open the impeller housing to find the impeller missing two vanes. Found one, will go searching for the other when I get the boat back home.

Look for my upcoming post “how to disassemble heat exchanger on Yanmar 2YM15”