Yanmar 3ym30 will not budge! Help...?

[RPFleming01]

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.

[Jim Cate]

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.

Jim

[Boatyarddog]

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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[Boatyarddog]

Originally Posted by Hard Rock Candy

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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[jellis23]

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!

[Johnbema]

Hi
I was just wondering...how do you think saltwater got in? From the water pump side or did waves splash into the rear exhaust port on hull?

If you are hydrolocked , how do you hand crank the engine?
Pull a glow plug then hand crank? Or you have to use a giant socket and wrench on main pulley?

Are there decompression levers on 3ym30?

Thanks!

[jellis23]

FIXED/SOLVED!!!!!!

Its been well over a year since i posted here but i wanted to bring closure to my issue and thanks to those who offered there help and expertise.

anyways, I failed to see the warning lable on the air intake of the engine (it was rotated upside down) saying WARNING! over cranking will cause water intrusion into the cylinders... or something to that effect.

Well, i cranked the engine, a lot, without closing the raw water seacock. (gross lapse of judgement) The engine sat for over a year with salt water filled cylinders then drained down into the oil pan.

The great news is that I pulled the engine. tore it apart to find a gallon of salt water in the oil pan (the dipstick had shown clean oil because water is denser than water and sinks silly!!)

but... the ONLY damage in the whole engine was:

-the mating surface of the exhaust manifold/heat exchanger was badly corroded, fixed by welding on new aluminum into the pitting then grinding flat and finish sanding on a piece of 220-600 sand paper on a sheet of glass

-2 valves needed replacing, the valve seats needed grinding

-And 3 COMPLETELY rotten pistons (i had to pound them out with a sledge hammer), replaced with new pistons and rings.

all bearings, guides, seals, etc were completely intact and uncorroded!! apparently the corrosion was isolated to areas where iron was in direct contact with aluminum and therefore the aluminum acted as a galvanic anode sacrificing itself while the iron remained perfectly intact (aluminum heat exchanger and pistons)

After major cleaning and rebuild I reinstalled and proceeded to take her from maine to the bahamas and back to nc putting 500 some incident free hours and only minor oil consumption.

[Compass790]

Thanks for posting the update. Good story & great news that pistons acted as anodes.