Rebuild, replace, repower

267
90
Sooke, BC
The little 1GM10 in my boat is shot, low compression, needs a rebuild. I have some options, thoughts from the esteemed SA folks?

Background: boat is on a mooring, about an hour's drive from me, so not exactly convenient to work on. i have nowhere to store, nor a trailer to put her on (without begging/borrowing/renting).

  1. Rebuild the existing engine - no idea what that's going to cost, teardown might uncover a whole world of extra pain (i.e. $)
  2. Replace with a good condition used 1GM10 - still a bit of an unknown, and likely more expensive than option 1, but I'd get a much newer engine out of it
  3. Replace with a new 1GM10 - very expensive, but a straight swap and the peace of mind of a new engine
  4. Replace with the 2GM20F I have in my garage - motor is unknown really, it runs and compression check etc show's it is good, but that's about it. Reasonably straightforward swap but it's a bit longer, different exhaust size etc so will still take a bit of work
  5. Replace with A.N.Other new engine, e.g. Beta14 - very, very expensive, but get a new, modern engine.
  6. Throw on an outboard on and admit defeat.
  7. Something else?

It's a 1974 C&C27, so regardless of how much money I throw at it, I'm going to get cents on the dollar for any route.

 

suider

Super Anarchist
We are going through this with a boat in the yard right now- what makes the most sense? And the short story is- it depends...

Why is your compression low? I mean, have you tried a leakdown test? I'm guessing not on a mooring, but that is going to give you the best indication of where to go. Not to get your hopes up, but it is completely possible for poor valve seating to give you low compression, especially on a one cylinder engine. So, at that point, pulling the head and re-lapping valves (or even replacing valves) makes a ton more sense (at least monetarily) than your other options. 

Assuming it goes further than that (ie, leakdown indicates rings, etc)........?? Ugh. It's the issue we run into all the time. Replacing rings on a 1GM is not a particularly hard job, but rebuilding yourself means you are warrantied by an asshole- and, depending on the age of the motor, still open yourself up to other failures down the road. I (generally) would feel a little better about the used motor option if you had an idea of the history- but at least the 2GM you have is an F- but you are right- that isn't the smoothest swap- it will take some alterations (but likely less so than the Beta and likely other brand re-powering).

Finally, I don't know why installing an outboard would be 'admitting defeat'... on a boat that size you could actually gain some interior space (depending on where the engine is located), lose some weight, and give yourself a project that is arguably a little more fun than the other options.

Try to find a way to do a leakdown test. Then you can just make a better determination of 'how shot' your engine is. That's where I would start.

 

Moonduster

Super Anarchist
4,823
229
It's not necessarily the case, as asserted above, that if you do your own rebuild your warrantied by an asshole - that's really up to you.

Here's my own thoughts on the options you provide:

  1. Unless the block is cracked, the costs to rebuild this engine aren't very high. If you do the work yourself, you'll have a good engine and the knowledge and incentive to maintain and repair it going forward.
  2. The challenge here is understanding the condition and history of a used engine. I would not pursue this option without getting a warranty on the used engine and then only if that warranty is in engine-hours, not months.
  3. This seems dumb compared to #1 unless your time is more expensive than your cash
  4. I expect this is a lot of work to modify the mounts and accommodate the major connections - fuel, water, exhaust and alternator. The increase in weight also needs some consideration and then you'll need a new prop, too. Given you're on a mooring, this could drag on a long time.
  5. This is 3 + 4
  6. Why not look at the outboard as the thing that allows you to have more time to do #1?

Generally, the problems you're likely facing are top-end. You can easily pull the head in half a d ay and have that rebuilt in a month or two at modest cost if you have your own tools and do your own work. Then, bolt the head back on and if the problem is fixed that was easy. If not, then pull the engine, buy the outboard and proceed with a bottom-end rebuild at your leisure.

 
I replaced a head gasket on a 3QM 30 (head, alternator, starter and injectors all rebuilt). It was not hard, and not that time consuming with planning.  Get the  manual, rent/buy a few tools and take your time.  Cost of rebuilds and parts was maybe $1,000 and that was three cylinders.  Runs fine now.

Outboards suck in an area with any kind of seaway.  Otherwise fine (except for some the aesthetics).

Good luck.

 

Rain Man

Super Anarchist
6,926
1,884
Wet coast.
The outboard option comes with its own set of problems.  You need something strong to bolt the bracket to, and may find that the transom needs re-inforcement beyond just a backing plate.  In addition, you will ideally need to control the engine from the cockpit somehow, as leaning over the transom to get forward and reverse probably isn't practical.  It may be difficult to raise and lower the engine without some form of tackle, and you'll need a 9.9 for a 27 if you need any grunt to motor against a current. A new 9.9 is about $3-$3.5K.  If you go this route get a Yamaha Hi-thrust, my 2000 9.9 still runs perfectly after 18 years of hard use in salt water.

Aesthetics wise you'll get this with an outboard:  http://www.lmyc.ca/the-fleet  Sadly, all these boats are now in pieces on the bottom or on the beach in White Rock B.C.

I would attempt the repair on your diesel.  

 

SloopJonB

Super Anarchist
65,127
10,613
Great Wet North
You have to put the boat ashore for this so just bite the bullet and do it. Yard rates are low this time of year. Trying to swap or rebuild an inboard on a mooring would be an exercise in insanity.

My first choice would be to rebuild the existing engine - do you know an experienced person who could babysit you through it?

Next best would be to swap someone your 2GM for a 1GM. Some cash either way, depending.

O/B would be an act of desperation IMO - will degrade the value of your boat a lot. Those are big 27's and people use their engines for a lot more than docking around here.

 
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Moonduster

Super Anarchist
4,823
229
Trying to swap or rebuild an inboard on a mooring would be an exercise in insanity - really?

A 1GM10 weighs in at 76kg (167 lbs). I have sails that weigh more than 76kg.

It's a piece of piss to use the main halyard and boom to lift it out of the boat and swing it into an inflatable dinghy.

What would be insane is to waste the money to haul and store the boat for a couple of months because of such lousy advice.

 

Ishmael

≈≈≈≈≈≈≈≈≈≈≈≈
48,205
9,467
Fuctifino
I redid the head gasket on our 3GM30F, no big deal. I took the head to Ben Gartside's shop and they checked for flatness and did a cleanout of the cooling passages, etc.

I think overall it took about a week and cost less than $250. There are a lot of boats on the hard at Westport right now, I bet you could get an empty slip for a couple of weeks for not much money. Much easier to do the job at a dock.

 

SloopJonB

Super Anarchist
65,127
10,613
Great Wet North
Trying to swap or rebuild an inboard on a mooring would be an exercise in insanity - really?

A 1GM10 weighs in at 76kg (167 lbs). I have sails that weigh more than 76kg.

It's a piece of piss to use the main halyard and boom to lift it out of the boat and swing it into an inflatable dinghy.

What would be insane is to waste the money to haul and store the boat for a couple of months because of such lousy advice.
Yeah, I've only yanked a dozen or so engines everywhere from an apple orchard to dockside to a fully equipped shop.

I'm sure you know a lot more about it.

 

Zonker

Super Anarchist
8,890
4,803
Canada
Well in this case, with such a small engine, why can't you remove when afloat?? (Assuming you can break the shaft coupling of course!). I wouldn't rebuild it on the boat. That is indeed madness.

Honestly I'd do a minor rebuild the 1GM. Maybe rings, maybe a head gasket, maybe lap valves

But it's a simple engine with 1 piston. You can rebuild it on the dining room table (cover with a piece of cardboard + a towel, otherwise your wife will yell at you).

Go to youtube and search for "Yanmar rebuild". I was surprised at how many instructional videos. Some are 2, some are 3GM, but they are similar blocks, same pistons/valves/injector etc.  




 
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267
90
Sooke, BC
It's definitely more than a valve seat issue, the crankcase is well pressurised, smoke at idle, more smoke under load etc. It's almost certainly the rings. I wasn't intending on doing a swap at the mooring, but the simplicity of a swap vs a rebuild vs a repower definitely has some bearing on things - a couple of days for a straight swap to potentially weeks for a repower since there are limited hours I can work on the boat.

 A brand new engine certainly makes no financial sense, however it does come with a very large dose of comfort for a very un-sailing-friendly wife, and two young kids.

I tried taking the boat to a yard to get some diagnostics done on it, they didn't even bother firing it up before telling me it wouldn't be worth fixing and to just repower. Not sure they even set foot on the boat.

Problem with rebuilding the existing one is the other horrors that get uncovered once you start getting into it, what starts out as a fairly straightforward rebore and fitting of an oversize piston turns into a reground crank, new rod and bearings, head rebuild...... potential scope creep and the not exactly inexpensive Yanmar parts could end up costing more than just getting a freshly rebuilt one (or a newer low hours fully tested one).

I might see if Ben up at Gartside will take a look and give me an honest appraisal of the options. Parting out the existing 1 cylinder and selling a complete and running 2 cylinder should go a long way towards the costs of a replacement of some sort if necessary.

 

Zonker

Super Anarchist
8,890
4,803
Canada
Use the 2GM for parts :)

I'd be very surprised if you needed to go up a piston size or reground the crank, new rod or bearings...Agree that would be a deal breaker.

If you disassemble the engine and find something catastrophic you're in no worse condition that you currently are, other than a few hours of work to investigate

 

olaf hart

Super Anarchist
Have you tested the low compression, or is it an assumption?

those engines blow a lot of smoke under load, like a dirty hull or prop,

could just be an injector as well.

check your data, then rebuild the thing, it’s easy.

 

suider

Super Anarchist
I tried taking the boat to a yard to get some diagnostics done on it, they didn't even bother firing it up before telling me it wouldn't be worth fixing and to just repower. Not sure they even set foot on the boat.
While I would hope they set foot on the boat, these days it IS becoming harder and harder to justify rebuild costs- although a little less with diesels.

I tell my guys these days to just replace carbs on smaller outboards if we suspect a carb issue, because (at $90/hr) the cost of the brand new carb swapped out can be cheaper than the time even to disassemble the old one- let alone cleaning, reassembling and reinstalling. Sure, with the bigger, more expensive carbs we still rebuild- and people will still accuse me of 'just replacing parts' - until I go over what it takes to disassemble and clean one properly.

However, if you DON'T have to pay the labor - it starts to make more sense. Hope you come up with a solution!!

 

A guy in the Chesapeake

Super Anarchist
23,965
1,165
Virginia
It's definitely more than a valve seat issue, the crankcase is well pressurised, smoke at idle, more smoke under load etc. It's almost certainly the rings. I wasn't intending on doing a swap at the mooring, but the simplicity of a swap vs a rebuild vs a repower definitely has some bearing on things - a couple of days for a straight swap to potentially weeks for a repower since there are limited hours I can work on the boat.

 A brand new engine certainly makes no financial sense, however it does come with a very large dose of comfort for a very un-sailing-friendly wife, and two young kids.

I tried taking the boat to a yard to get some diagnostics done on it, they didn't even bother firing it up before telling me it wouldn't be worth fixing and to just repower. Not sure they even set foot on the boat.

Problem with rebuilding the existing one is the other horrors that get uncovered once you start getting into it, what starts out as a fairly straightforward rebore and fitting of an oversize piston turns into a reground crank, new rod and bearings, head rebuild...... potential scope creep and the not exactly inexpensive Yanmar parts could end up costing more than just getting a freshly rebuilt one (or a newer low hours fully tested one).

I might see if Ben up at Gartside will take a look and give me an honest appraisal of the options. Parting out the existing 1 cylinder and selling a complete and running 2 cylinder should go a long way towards the costs of a replacement of some sort if necessary.
IMHO - I'd plan on the machine work for all bearing surfaces.  That's a small, simple motor, and *any* machine shop can do the minor amount of turning ( assuming that you don't have severely galled bearing surfaces) that would be necessary to resurface the crank, resize the big end of the rod, new piston/wristpin bushing/rings, and to lap/replace the valves/seats/guides.  If it's running now, and there are no breaks/cracks in the block - the machine work for this should be less than $1K - I don't know how much a piston/rings are - but would be surprised to see the piston kit be more than a couple hundred bucks.  A new replacement engine is close to $5K - if you do the work, I think that you should be able to do a complete rebuild on this one for $1500 or so. 

 
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