Rebuilding a 3YM30?

[Ryban]

I looked at a heavy displacement 28-foot boat today. Everything is pretty great about the boat, except for the engine. It's less than 15 years old, and only has 140 hours on it, but I think because it wasn't used much and probably just let to sit for a very long time --possibly without oil (or with water in the oil?) -- it has corroded on the inside and is seized up.

The engine will probably need to come out and be re-built if I go forward with a purchase. What sort of costs should I expect for this job (just the rebuilding, not the extraction)? Would I be better off buying a re-built or new engine?

Just need people's 2-cents. The boat is discounted accordingly and I may push further on that price.

[ThereAndBack]

Just a datapoint, not saying it is best one way or the other but...

I recently replaced the engines in my boat with Yanmar 3ym30ae models. Since you just need a like for like engine, you can just buy the bobtail engine. I have the price on my invoice listed at $6,784.00.

[Flod]

It’s a good engine and it shouldn’t be that expensive to get it running again. Even if it turns out to be beyond economical repair you still can sell parts of it to pay for a new engine

[MikeHoncho]

Is check the rest of the boat for water damage.

[Compass790]

Originally Posted by Ryban

I looked at a heavy displacement 28-foot boat today. Everything is pretty great about the boat, except for the engine. It's less than 15 years old, and only has 140 hours on it, but I think because it wasn't used much and probably just let to sit for a very long time --possibly without oil (or with water in the oil?) -- it has corroded on the inside and is seized up.

The engine will probably need to come out and be re-built if I go forward with a purchase. What sort of costs should I expect for this job (just the rebuilding, not the extraction)? Would I be better off buying a re-built or new engine?

Just need people's 2-cents. The boat is discounted accordingly and I may push further on that price.

It depends on how bad it is internally. Yanmar parts prices are very high. If you have more time than money & can do all the work yourself it may be worth doing but you probably wont know until you strip it.
You could price up the parts you'd probably need and get an idea.

If you cant do the work yourself a new or rebuilt engine is a better bet.
If you can find a good used engine it can be a good way to go if you know how to tell the good from the bad.
The only safe thing to do is price in the cost of a replacement.

[Ryban]

Good responses. I don't think I'm allergic to the idea of just swapping in a new engine, and then hanging on to this one to re-build or sell as-is. Maybe I should reach out to a mechanic for their thoughts.

I haven't rebuilt an engine before but I'm not afraid to take it apart and give it a go -- how technical is the task (e.g. does it require special equipment)?

[EngineerRetired]

This a tough call. If the engine is seized you may be looking at a complete tear down, a lot of machining work and then very expensive parts. On the other hand, you might get by with a clean up, honing the cyl. walls and new rings. A tear down is the only way to really know.


With that said, I've seen guys dump penetrating oil into the top of the cyl. "rock" the crank back and forth, break it free and once done flush the engine to get rid of the rust and fire it up. What do you have to lose trying this, nothing, the engine is useless as is.

[Fore and Aft]

How did the engine get water in it? I couldn't imagine anyway unless the boat half sunk?
I agree with Engineer Retired, I have seen dead engines brought back to life again.
Cheers

[Compass790]

Originally Posted by Ryban

Good responses. I don't think I'm allergic to the idea of just swapping in a new engine, and then hanging on to this one to re-build or sell as-is. Maybe I should reach out to a mechanic for their thoughts.

I haven't rebuilt an engine before but I'm not afraid to take it apart and give it a go -- how technical is the task (e.g. does it require special equipment)?

Ummm. If you have no mechanical experience there is quite a bit to getting it right. it's not the getting it apart that is the problem, it's the re assembly correctly. I can send you a free copy of the workshop manual if you PM me yr email that will tell you what is involved.
Having said that you could try what rtd engineer suggests.

[FPNC]

I would be very suspicious of the exhaust system as being the root of this engines demise. I see no vented loop in the photo and the drop to the muffler from the riser looks marginal at best. Also, drop needs to be increased above the minimum when you set the muffler off to the side of the engine in lieu of behind the engine.

[Ryban]

I'm pretty certain based on my experience with boats and everything I've seen on this boat, that it hasn't been submerged or partially submerged at any point.

Could be the exhaust, I have another photo that shows its location, but it's hard to tell its height relative to the engine in the photo I have.

Could it also be possible that condensation is the culprit? That the engine was not kept full of oil for some time, and humid air and cool nights slowly took its toll?

[EngineerRetired]

Ryban,


I've rebuilt a ton of Yanmar engines, mostly in small tractors but they really aren't any different internally. You can buy all new internals, (cyl. sleaves, pistons, rings, all bearings, brand new valves and valve springs, all gaskets and seals, pretty much everything you need for $500 to $600 as long as you do NOT buy from Yanmar directly.


There are several third party vendors with top quality parts and the same guarantee you would get from Yanmar. Check Amazon and Ebay.


With that said, there are a few special tools that will make the job a lot easier. You would probably want to take the head to a good machine shop and and have them make certain it is flat, but with the few hours you are reporting that may be not be needed. Simply lay a good steel rule across the deck of the head and look for gaps. In addition you will probably want them to press the old cly. linings out and new in.


With a bit of effort, a rental tool or two and some time, you could have a near new engine for less than $1,000 to $1,500 US.

[Hesti]

While the engine is out - check the seacock. It looks - very green.

Are the parts that have been taken off the engine still around? If not - there will be additional cost in case of a rebuild.

It is a pitty, that engines is nearly new.

[Wotname]

Originally Posted by EngineerRetired

.........
With that said, there are a few special tools that will make the job a lot easier. You would probably want to take the head to a good machine shop and and have them make certain it is flat, but with the few hours you are reporting that may be not be needed. Simply lay a good steel rule across the deck of the head and look for gaps. In addition you will probably want them to press the old cly. linings out and new in.
..........

One small correction to the otherwise good advice - the 3YM30 does not have cylinder liners. If the bore is damaged, oversize pistons are available (although the cost may be staggering).

[Compass790]

Originally Posted by Ryban

I'm pretty certain based on my experience with boats and everything I've seen on this boat, that it hasn't been submerged or partially submerged at any point.

Could be the exhaust, I have another photo that shows its location, but it's hard to tell its height relative to the engine in the photo I have.

Could it also be possible that condensation is the culprit? That the engine was not kept full of oil for some time, and humid air and cool nights slowly took its toll?

Na condensation wouldnt make it look like that at least as far as I can see.
Looks very much like salt water intrusion but hard to see as I cant blow up pic.

Good call on trying to find out what tractor or digger etc engine the 3ym30 is based on & buying the parts frm non-Yammer sources.