Yanmar 2GM Rebuild

[Dan McNece]

While I admire Cape Dory's, I instead own a Nor'sea 27. It was in need of quite a bit of work when I bought the boat.

I removed the engine from the boat to replace the fuel tank under it. I thought I could clean up some rust and repaint and it would be good. But when I started looking closer, I decided it needed a lot more work.

The Yanmar 2GM is in a lot of boats. Maybe someone here on this forum has one in their boat too. Surprisingly, this engine of mine was still working when I pulled it, but I'm glad I decided to tear it apart as there were plenty of issues that could have killed it, for good. Not only that, this engine only had 730hrs and the work I did was necessary to keep it going. Others have described it has neglect. I've only had the boat since April 2012 and ran the engine a total of 10hrs or so. So the issues were inherited from the previous owners. I'm not a mechanic. I'm active duty in the Army at just over 18yrs in.

If your engine is looking tired or sounding sluggish, reworking it might not be a bad idea. If I could do it, I'm sure others can just as well with a lot of time and a lot more of patience.

Here's what I had to work with.

Exhaust had a lot of built up rust and here you can see it was partially clogged with rust and carbon.


Here's what old and new exhaust mixers looked like together.


clogged cooling passages.


There was supposed to be a zinc in here somewhere.


Carbon buildup almost completely blocking the exhaust valves. Oily residue on the intake valves from a previous oil leak at the valve cover gasket.


Rust all over the block.


and, the biggest surprise was finding one of the pistons with a crack. Again, the engine was working like this too. No telling how long ago this happened.


I've read some advice before by other boaters who say that if an engine is running, just to leave it alone. If I took that advice myself, it was just a matter of time before something failed and I'd have to replace the whole engine. From what I have researched during this project, I'd say it's safe to say there's a lot more to maintaining an engine than doing oil and filter changes. Remember that diesels have to be run hard and not sit too much at idle. I believe my engine may have ran at idle too much and caused a lot of that carbon build up.

Another note is making sure the propeller is right for the engine, transmission and the boat. Size and pitch does matter. As I was reading up on the subject, I believe my 3-bladed prop (Michigan Sailor) that was mounted when I bought my boat, may have been over-pitched. The 2-bladed prop (Federal Sailor) stored on the boat is a 13x12 and may have been original to the build and someone kept the same size/pitch with 3 blades. The added surface area of the 3-blade prop should have changed the settings on the prop. I calculated myself that a 13x10 or 13x11 may have been better for the engine/transmission setup. I know other Nor'sea owners went with a Campbell sailor sized at 14x7.

I'm happy to say, that after a test run of my engine, it is sounding beautifully now and really looking forward to putting it back into service.

You can see more pictures/info on what I did over the past several posts to my blog at: http://norsea27-rhapsody.blogspot.com

This is the result of a few months of work on my Yanmar 2GM.





last, but not least, a short video showing it running.
https://www.youtube.com/watch?v=iejk2PM5b-8

[Jim Walsh]

That's fantastic, Dan, thanks for sharing your project with us. With your choice of color I'd be hard pressed not to put a Caterpillar badge on it, just to watch people scratch their heads. I'll bet you inspire others to consider taking on this task themselves. Great job.

[gates_cliff]

First, that really is an impressive rebuild. I have a Westerbeke 13 in my boat. Last fall when I had the engine winterized by Engines Unlimitd in Galesville, I asked Don, the owner what he thought of the condition of the engine. He said it was great and would run forever. He's an excellent mechanic and I'd never question his word but with what you discovered on yours it does make me wonder.

[Dan McNece]

Cliff,

Since the bulk of the work I did was on the head, an inspection of that couldn't hurt. I would suggest seeing if you can get a camera like what's used to inspect plumbing. I'm not familiar with your engine but if you can inspect the head through the air intake or from the exhaust side, you could see what the passages look like. Looking for excessive carbon and/or rust buildup could help keep you from major disassembly. Depending on how the injectors are installed, it might be possible to remove them to inspect the condition of the pistons. Also keeping you from major disassembly again.

Then again, if your engine exterior looks good, it might be. I had a LOT of exterior indicators of trouble. I have also heard it's best to leave a working engine alone, but I think small inspections first could be helpful. Not sure about your engine, but for my Yanmar, the head gasket is $70+ and one time use only. Meaning, once the head bolts come off, that's more $$ you're shelling out to put it back together, along with any other gaskets along the way. Like the copper gaskets Yanmar uses.

Hope this helps you and others.