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Old 30-07-2018, 11:40   #16
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Update! Engine is out and sitting in my garage!
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Old 30-07-2018, 15:24   #17
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

^^ well done, now the fun begins

But please tell me you didn't lift the engine with your dog lead clip
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Old 30-07-2018, 16:48   #18
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

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Originally Posted by leveche420 View Post
Thank you! I hope so! I want to do it right! I am a bit intimidated by this engine project but at the same time I am getting motivated when I hear that is doable.

One of the first things I am going to try to do is check the compression. I think I found a compression tester in the boat, so the previous owner may have already checked and that's why the brooker thought the compression was low

I am going to start researching where in the US I can get parts for this engine

What part would you recommend to change for a good solid rebuild? Would you help me start drafting a list of parts that I will have to replace?
it's best to look for whats wrong than just have a blanket approach. You need a workshop manual & check tolerances. Probably you can find one online. Things I would start on would be exhaust elbow, check valves & seats & ring gaps. Piston diameter & bore state. Big end bearing check. Also main bearing tolerances. Agree with Wotname &others re gearbox. You shouldnt need to touch it. Unless it was run without oil.I think the Yanmar distributor is in Georgia so you are close anyway.
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Old 30-07-2018, 18:24   #19
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

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it's best to look for whats wrong than just have a blanket approach. You need a workshop manual & check tolerances. Probably you can find one online. Things I would start on would be exhaust elbow, check valves & seats & ring gaps. Piston diameter & bore state. Big end bearing check. Also main bearing tolerances. Agree with Wotname &others re gearbox. You shouldnt need to touch it. Unless it was run without oil.I think the Yanmar distributor is in Georgia so you are close anyway.
Thank you! I already have the workshop manual. I have never checked tolerance before so I better start researching . The starting points you suggested is great feedback for me. Thank you very much. Just from the outside I can tell I have to replace the oil and fuel pipes as they are so rusted that one is even broken. I think one of the issues with this engine was compression so I think I will have to check the head, rings, pistons, valves, etc. I also want to rebuild the water and and maybe fuel/injection/oil pumps?

To be honest I dont have an strategy yet so I wont start until I have one... and I clean my garage a little bit and make room for all the engine pieces

Thanks all for your help
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Old 09-08-2018, 18:51   #20
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Update! A friend and I started taking apart our yanmar 2qm20. We are trying to remove the head but even though we removed all bolts and nuts the head is not coming out. It seems to be sticked to the engine block. Are we missing anything here? Any idea on how to get the head out?
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Old 09-08-2018, 19:23   #21
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Put the injector(s) back in, don't worry about the fuel line and try turning the engine over by hand (hand crank etc). The compression should push the head up.
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Old 09-08-2018, 19:26   #22
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

If that isn't enough, you can try gently tapping the head up with a hammer or remove the studs and hammer sideways (again sort of gently).

Using a cold chisel between the head and block is not recommended but some get away with it

A calibrated tap with a hammer in the right spot works wonders .
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Old 09-08-2018, 19:30   #23
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

If you have all the bolts out (probably 6), then the head is just stuck on by the gasket. If you have studs, rust between the stud and the head could be holding the head on.

If you have bolts, if it were me, I'd just take a wood chisel, put the pointy end at the joint circled in red, beveled edge up and flat side parallel to the block surface and give it a few taps; the head should 'break loose' with little fanfare.

For the more cautious or inexperienced, you could also use a longish prybar (yellow) and block of wood or length of pipe (maroon), and just pry it off.

There're lots of other ideas; I just prefer the quickest and most direct...
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Old 09-08-2018, 19:54   #24
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Re post #22, I should have added to use a piece of wood between the engine and the hammer.
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Old 10-08-2018, 05:49   #25
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Thank you so much guys for taking the time to even edit a photo to help me. I'm impressed, highly appreciate it. I hope I will be able to help others once I gain enough knowledge and experience refitting old disel engines. This is fun!
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Old 10-08-2018, 06:52   #26
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Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Assuming all the bolts are out, I bet it’s stuck on the locating pins.
Logically using engine compression is likely the best bet, but I’d lay a 2x4 on the side of the head and smack it with a 5 lb hammer, then go to the other side. If that doesn’t knock it loose, then start investigating, you missed something that is holding it.
Do not put something sharp like a screwdriver and try to pry the two sides apart, likely that will end badly
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Old 11-08-2018, 03:48   #27
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

Update! I found a nut/bolt that I forgot to removed... Upppssssss.... Once I removed the head came out with just a little bit of tappimg and prying. See attached pictures to see how the head looks like. More to come
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Old 12-08-2018, 01:12   #28
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

The spot on the lower right hand side just above the water passage hole looks a bit suspicious and may indicate a leaking head gasket. Put a steel rule across the raised bit on the circumference of the cylinder and a strong light behind it and see if there is a gap between the surface and the ruler. Alternately using a very fine grit sanding block clean up the circumference and see if there are any gaps in the circumference. Post an image please.
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Old 12-08-2018, 14:24   #29
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

While you have the unit out, take the trouble to replace the gearbox rear mainseal. My 2qm20 has the other type of gearbox to yours but I think the same advice applies. I was lucky when replacing my clutchplates a few years ago to find a very experienced yanmar mechanic (who shortly thereafter retired) and that was his advice to me - otherwise those gearboxes are almost indestructible.
Get a piece of flat bar steel and drill it to match 2 of the outside holes on the drive flange - this is your lever ( once bolted on) against which you can use a socket to undo the main shaft nut in order to replace the seal. As I recall it was a simple procedure - i think i had to smack a screwdriver through the old seal to lever it out.
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Old 12-08-2018, 15:00   #30
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Re: Yanmar 2QM20 - Should I rebuild or replace it? Maybe convert to electric?

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The spot on the lower right hand side just above the water passage hole looks a bit suspicious and may indicate a leaking head gasket.


May? I’d bet lunch on it
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