Yanmar 2qm15 Rebuild

[Redbeard33]

As I have said in previous posts, my 2qm15 was in need of some attention so I decided to pull it this winter for a once over. I decided to post some pictures and talk about my stategy so that some may see the process and others may critique my technique. The first 2 pictures are from the engine removal, the third is mounted on the engine work stand, the 4th is as the engine sits now, stripped almost down to bare block the 5th picture is of the head removed

[Redbeard33]

what is the preferred method of prepping the block? grinder with wire brush attachment followed by acetone (degreaser) primer then paint? also do i paint parts seperately then assemble or assemble and paint whole?

[Laidback]

The last picture of the Head reveals a pretty clean combustion chamber.
Only one question regarding the arrowed area below one of the Stud holes - is that oil or corrosion ?
PS Are you going to remove the valves to see if they need the seats ground - or at a minimum to lap them in ? - worth doing now that you have the Head off.

[Redbeard33]

yeah i was happy to find the cylinders and head in good shape, that spot you pointed out is just an oil drip but the nearby water passages are full of scale, should I physically pick out the scale with a coat hanger or something and then use a solvent to remove the gasket residue or can I scrape the head face without worry?

[capnorv]

Great pics! I did a 8hp about 13 years ago, still running strong last I heard. I descaled with screwdrivers and awls, coathanger might work, or stainless filler rod ground to edge. I got as much debris out with a magnet as I could, then flushed, but I was still in the boat, on a stand air would probably work. Definitely check the valves, which was my slow starting problem. In my case reringed, main bearings, gaskets, and injector finished the job, more or less.

[Laidback]

Originally Posted by Redbeard33

yeah i was happy to find the cylinders and head in good shape, that spot you pointed out is just an oil drip but the nearby water passages are full of scale, should I physically pick out the scale with a coat hanger or something and then use a solvent to remove the gasket residue or can I scrape the head face without worry?

Unfortunately the 'scale' is hard to remove past the parts you can actual see.
You can scrape the face of the head (as long as you don't dig into the metal)
How about the valves and their seats? giving them an overhaul improves compression, consumption etc etc.

[Redbeard33]

I have ordered the parts that I need for sure (gaskets etc.) and will take the head to the local diesel shop i am ordering parts from to verify that the valves are in good shape they appear good to me but I am not an expert, also the master mechanic i spoke with when ordering parts suggested i sand the inside of the cylinders with 320 grit wet/dry paper he said it helps the rings hold compression and oil compared to mirror smoth walls, is this something i could reasonably attempt or is it a task that one should attempt only after 20 years experience?

[Laidback]

Originally Posted by Redbeard33

I have ordered the parts that I need for sure (gaskets etc.) and will take the head to the local diesel shop i am ordering parts from to verify that the valves are in good shape they appear good to me but I am not an expert, also the master mechanic i spoke with when ordering parts suggested i sand the inside of the cylinders with 320 grit wet/dry paper he said it helps the rings hold compression and oil compared to mirror smoth walls, is this something i could reasonably attempt or is it a task that one should attempt only after 20 years experience?

The valves may appear to be in good nick - but unless they are taken out, one cannot see the seating faces on both the valve and the head - this is an easy job to remove, lap in and replace.
Sanding the Cylinder walls is done to remove glazing, normally this is done with a rotary honing tool. Perhaps an 800 wet paper would better than 320 , (if being done by hand ) all that is necessary is to remove the 'shine' - once done remember to oil the walls.

[foggysail]

You made a wise decision taking the head to experts. Yes, I agree the valves should be checked, even reseated. But I have seen valve guides ruined with grinding compound by DIYs.

Next suggestion only because you have the thing torn apart, consider removing the pistons (mark the bearings and piston position before attempting removal), take them to a shop and get them fitted with new rings. Of course, if the engine does not have many hours (maybe less that 2K hours?) just leave them alone. If you do remove the pistons, you may need a ridge reamer to remove the ridge that forms at the top of the cylinders.

Foggy

[capnorv]

I sanded my walls on reassembly by hand. Easily done as long as you don't get overzealous in one spot. Gently, gradually, all around. I'm not to sure low hours on rings are a good thing, I lunched a 25 year old engine with less than 700 hours once, because a mid ring broke. I had just purchased the boat 10 hours before, changed oil and filter and headed out for our one month honeymoon... we're still together. I think steady use and maintenance are a better argument for longivity. Rings are cheap, why not go ahead and rering it? Just my opinion, while it's down.

[Redbeard33]

update...... I found the critical parts (valves rings cylinders etc) to be in good shape and have reassembled and painted the block. all rubber fuel and coolant lines to be replaced along with the usuals (zinc, impeller, fuel filter etc) and alternator starter and injectors being rebuilt the injector pump was left alone as per numerous warnings and lift pump cleaned and painted, is a spare diaphram for the lift pump wise to keep on board or just overkill? also adding a full complement of guages as this engine came stock with only idiot lights....more pics to follow

[Arch Stanton]

Originally Posted by Redbeard33

update...... I found the critical parts (valves rings cylinders etc) to be in good shape and have reassembled and painted the block. all rubber fuel and coolant lines to be replaced along with the usuals (zinc, impeller, fuel filter etc) and alternator starter and injectors being rebuilt the injector pump was left alone as per numerous warnings and lift pump cleaned and painted, is a spare diaphram for the lift pump wise to keep on board or just overkill? also adding a full complement of guages as this engine came stock with only idiot lights....more pics to follow

That looks fantastic! I have the same engine.

I removed the official (non-copyrighted) 2QM15 Yanmar Service Manual from the binding and made it into a .PDF on the scanners where I work. If you'd like a copy let me know and I'll PM you the link.

[Redbeard33]

i actually have a copy that you sent me in a previous thread about this model engine, i had it printed and bound at kinkos and have used it every time i picked up a wrench. which is actually a good point to make....it can be a little intimidating to take apart the most expensive piece of equipment on you boat and service it yourself however with a good service manual, parts manual, and a knowledgeable local deisel shop there are only a few jobs the boat owner cant do to their own engine, marine diesels are fairly simplistic (its all relative) and anyone planning a long distance passage should get a service manual and get to know their engine well

-thanks agian arch that manual has been invaluable

[steve_hendry]

Hi Redbeard,

Who is your local diesel shop? I have a 3QM30 in my boat.

Steve

[Redbeard33]

waterway power center off generals highway in annapolis, the head guy there klaus is a diesel god and will take care of you (i had the added benefit of living 1/2 mile away) Also if anybody in the ches. area needs any work done on starter or alternator's theres a place in glen burnie that will rebuild them CHEAP i had my starter and alternator done for about 60 a piece but they were completly redone bearings solenoid relays and reguators, considering the $1300 cost for a new starter i think its worth the trouble to get it done when and where you want, oh yeah that place is called "glen burnie carb and generator" ask for butch