Rebuild of Yanmar 3QM30

[Richhh]

Am contemplating a total rebuild of a YanMar 3QM. Any one done it and what are the 'problems' to be encountered and any advice you can offer.

With all those 'over-engineered' and 'wierd' seals and gaskets, it seems this is not going to be a straight-forward rebuild.

Any comments appreciated.

[rleslie]

Rich

Define rebuild. Are you intending to get, into the cylinders, replacing rings, etc or do you just want to replace raw&fresh water pumps, sensors, belts, heat exchangers, etc.

Roger

[Alan Wheeler]

And if you don't mind, Why the rebuild??? What is the fault and why???

[Richhh]

Total remachining.... boring of cylinders, new pistons if necessary, total valve overhaul, line-boring of crank journals if necessary, etc. A soup to nuts precision rebuild.

I dont have all the necessary machining capability so I will have to send some parts out, etc.

Just concerned with all those zillions of seals, etc. .... and obviously hidden problems that I'll uncover. I avoid Japanese 'engineering' whenever possible .... too over engineered, too fragile, more complicated than necessary, etc. Thats why Im looking for someone who'se been totally inside one.

[Richhh]

Alan -
Engine hours are about 4000 but I really dont know the entire history. Was overpropped probably for most of its entire life.
With 4000 on it, its probably getting close to rebuild/replace time. I have the time to do it now and dont want to get into the hassle after I cut the docklines.

[Boracay]

I had a Yanmar that I put into my ferro yacht rebuilt many years ago.
I thought that just because it was old and looked rough it needed a rebuild.
It was a devil of a job getting the engine out and taking it to the dealer, and when I got it back it there was no improvement.
So unless you are getting clear indications that your engine needs a rebuild consider if it is worth the trouble and expense.

[Alan Wheeler]

Hmmmm, 4000hrs is getting up there for a wee 3. And especially if it was worked hard while overproped. It is hard on main bearings. It can also leed to holes in the pistons, but that is either a go/nogo failure.
However, as Chris has also stated, if it is not showing any major signs, it still could have a lot of life left in her. At least with Deisels, it is rare that you get a sudden failure. Not impossible, just rare.
As for the motor, you will find no hidden surprises. Nor a zillion seals etc. They are well engineered and not overly complicated. I suggest a strip down and send the block to an engine reconditioner or engine machine shop or what ever you call them your way. I imagine the crank will need ground and then oversize bearing shells to suit. You won't want the Journals bored. IF cylinders are bored, then it will mean new pistons.

Mate, I know of a 3 cylinder Yanmar here for sale that has done next to nothing in hrs. It is a few years old, but I doubt if it has even reached 300hrs. I know the motor, the boat and the owner well and can vouch for them all. The owner doesn't want a lot for it. I wonder if it would be cheap to get over to you.
What is it going to cost to recon yours???
They are about NZ$13K new here. You would probably get this one for NZ$4.5-5K. That's about US$3500 at most to you. Let me know if you want to pursue it and I could investigate it further for you. Just a thought.

[Richhh]

Thanks Alan -
Yup, 4000 hours would translate to over 250,000+ miles on land and thats just about the limit of a diesel, even a land station steady state prime mover. Total expected rebuild costs should be somewhere near US$4K, much better than a new engine. Plus, I'll know what I have when done, especially if I 'micro-polish', it should be better than a new engine. Too bad the Yanmar isnt a 'sleeved' engine. Just looking for info from someone who actually has done it .... as there are 'always' tricks and traps.