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Old 15-01-2015, 19:25   #16
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Thumbs up Re: Yanmar 3ym30 will not budge! Help...?

Had the same problem with my boat two years ago, after it sat for a few years. Disk connected the transmission engine turned over fine. Replaced the transmission has run fine since. Good luck.
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Old 15-01-2015, 19:43   #17
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Re: Yanmar 3ym30 will not budge! Help...?

The above post reminds me: it is even possible that your damper plate has failed, and is jamming things up progressively. You will need to part the tranny from the bell housing to check that out.

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Old 18-01-2015, 23:41   #18
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Yanmar 3ym30 will not budge! Help...?

I believe from what you've said that when you laid the boat up for a couple years, that one or more of the valves were open enough to allow air, which has moisture in it to Rust the cylinder wall of a cylinder or two.

As you cranked it a bit at a time, the piston moved up enough to scrape the rust off the wall(s), enough to add enough rusty debris to block any further movement up the cylinder, as the space between the cylinder head and piston is very tight at the top.
That's why the compression is high in a diesel because of this very tight space.

So that rust may have plied up in there preventing further upward movement of the piston.
How to remedy this, or inspect is a bit of a challenge.

I would think that you could try to get it to move back to where it was, by reversing the rotation with a socket and ratchet or breaker bar on the crank bolt.

If it's stuck tight, pull the valve cover and inspect, you might see some rust in this area as well.
If so, pull the head, clean out and replace the gasket.

If that isn't the cause, drain the oil and look for metal flakes in the drippings, could be a spun bearing. Hope not.
Possibly a partially seized piston, or rings.
You can try to inspect thru the glow plug area, with a boroscope, but don't think there is direct access to the cylinder there,
As most diesels have a pre combustion chamber.



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Old 20-01-2015, 01:53   #19
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Re: Yanmar 3ym30 will not budge! Help...?

Quote:
Originally Posted by Hard Rock Candy View Post
The twenty horse 2 cylinder Yanmar drives the injector pump directly off of the cam. in other words, the pistons on the pump are lifted with special lobes of the cam. No one has mentioned the simplest thing. That could be, one of the pistons is rusted into the cylinder. It does not take much water to do the job and you did say that after working on it you left it sit for a while. You may have to remove the head on this one. They are a really simple engine to work on. Mac




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Old 30-07-2017, 22:00   #20
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Re: Yanmar 3ym30 will not budge! Help...?

I thought i should post an update here even though it's been a few years now from my initial post.

The engine was just finally completely put back together today for the last time....

I tore the motor down and decided to do a complete rebuild. Checked the oil and 'looked clean' but that's because the gallon of salt water that was in the block was under the oil... The engine DID go into hydrolock.

The reason it wouldn't turn over after i pulled the glow plugs initially was because in the few weeks or so that it sat the aluminum pistons had already seized in the cylinders.

It proceeded to sit for another 8 months before i took the head off and surprise! had to pound out the pistons with a sledge. Amazingly though the aluminum pistons and heat exchanger seemed to act as galvanic anodes and almost completely saved the rest of the engine from any corrosion whatsoever!

The head did need to be replaced as the valve seats (which are not replaceable) were too pitted even after machining but doing the whole job myself still cost thousands less than yanmars rebuild quote.

So now were loading our 2 boys 7/4 on the boat and heading south away from the maine winters hopefully with a refreshed and reliable diesel engine

Thanks for all the input!
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