Hi From Down Under

[Wotname]

Originally Posted by Gregted

.............
I would have thought if the piston is locking up the engine that after the conrod end was disengaged that would take the stuck piston out of the equation and allow the motor to turn over the last bit of the piston stroke.

Maybe it is at BDC but I thought it had a bit more travel. That could explain why we can't move the piston down any further.

Might have to concentrate more on upward movement...

Yeah, maybe at BDC or so close to it that is doesn't matter. The picture in your post #65 is inconclusive but it does show that it is at least close to BDC.

Perhaps making up a 'yoke' of hardwood so that you can apply hammer pressure to both lugs of the conrod might help by allowing the force to be applied evenly to the conrod.

[Wotname]

Originally Posted by Gregted

......

Might have to pull the P.T.O. pulley and have a look inside.

...

I had a lot of trouble finding a suitable tool to remove the PTO nut. I wasted a lot of time trying to kudge up something when I should have bitten the bullet and made a suitable 'socket' from the get-go.

In hindsight - my advice - buy a suitable 6 point impact socket, cut it to suit with an angle grinder and weld some support to the 2 remaining flanges.

Read here for more detail (especially the last page) - https://www.cruisersforum.com/forums...ut-188284.html

[skipperpete]

Having never worked on this model of Yanmar, I’ve been keeping out of the way while more informed people have been offering excellent information but the bit about not being able to rotate the crankshaft caught my attention. If a piston is seized in a cylinder and still attached to the conrod there will always be a tiny bit of crankshaft movement available, more at TDC and BDC than mid stroke….. but always that tiny bit of rotation. When there’s zero movement or rotation it implies that the crankshaft main bearings might be seized…. It could also be the conrod bearing too but at bdc or tdc water leaking down past the piston rings or past the liner orings often misses the conrod journal…. The main bearing journals are more exposed to the “rain”. If there’s no endfloat and absolutely no rotation, take it easy with trying to turn it until you loosen off the main caps. This might not even be possible on your engine if the main bearings are in carriers like the GM yanmars. Good luck with getting her moving again.

[Wotname]

Good points SkipperP -

For future reference, in these old Y series, one of the mains is located (pressed) in a carrier behind the flywheel and the other is pressed directly into the crankcase.

[Gregted]

Originally Posted by Compass790

Sorry Gregted should have said get a plastic or nylon ball valve for your raw water inlet line. Much less troubleome than metal. Grizzled old boatbuilder told me that. He tells all his customers that when replacing skin fittings.
Whats the big end journal like? If its rusty that is a problem, needs to be polished to a high shine.
Bit surprised you couldnt move piston but yea 20 ton jack will if whacking doesnt.

We will look for another bronze ball valve and try and get one with a plastic ball. I think we'll fit this one for now. I just don't like the fact that we cannot shut off the raw water inlet atm.

The big end looked good. Light surface rust but the conrod end fell off the crank with no problems so I think that is all ok. We will def polish it all before starting.

I was surprised also. I thought I might get some slight movement between the conrod and the crank even if it is at bottom but no movement at all. Makes me think the seizure might be elsewhere.

We will take the front cover off and have a look.

Looking more like the motor will be coming home this weekend..

[Gregted]

Originally Posted by Compass790

The starter shaft has a sprag bearing on it ( clutch bearing). Better to use pto shaft alright to try & turn it. It maybe the problem is in the gearbox thats stopping it from turning but you can take front engine cover off & look at the parts in there.
Study the diagrams in your workshop manual. With water in the oil you need to check your injector pump is moving as well.

The gearbox seems to engage and disengage from the prop shaft with no problems but we'll see more when we disconnect it from the motor before we attempt to take the motor home.


I will apply pressure to the PTO pulley this weekend and see if that helps.


The injector pump will get a look at as well as anything else we can think of before it goes back into service.

[Gregted]

Originally Posted by Wotname

I had a lot of trouble finding a suitable tool to remove the PTO nut. I wasted a lot of time trying to kudge up something when I should have bitten the bullet and made a suitable 'socket' from the get-go.

In hindsight - my advice - buy a suitable 6 point impact socket, cut it to suit with an angle grinder and weld some support to the 2 remaining flanges.

Read here for more detail (especially the last page) - https://www.cruisersforum.com/forums...ut-188284.html

Thanks for that link. I will mod something similar when we get to that nut...

[Gregted]

Originally Posted by skipperpete

Having never worked on this model of Yanmar, I’ve been keeping out of the way while more informed people have been offering excellent information but the bit about not being able to rotate the crankshaft caught my attention. If a piston is seized in a cylinder and still attached to the conrod there will always be a tiny bit of crankshaft movement available, more at TDC and BDC than mid stroke….. but always that tiny bit of rotation. When there’s zero movement or rotation it implies that the crankshaft main bearings might be seized…. It could also be the conrod bearing too but at bdc or tdc water leaking down past the piston rings or past the liner orings often misses the conrod journal…. The main bearing journals are more exposed to the “rain”. If there’s no endfloat and absolutely no rotation, take it easy with trying to turn it until you loosen off the main caps. This might not even be possible on your engine if the main bearings are in carriers like the GM yanmars. Good luck with getting her moving again.

Conrod end cap is removed and still no movement so conrod should not be the problem.


I thought as you did that it would be unlikely that sea water would get to the conrod enough to rust it but we are looking at all possibilities.


It really feels like more that the rings rusted to the bore so we will probably be bringing her home this weekend and performing a full tear down and rebuild and will certainly be checking the mains.

[Gregted]

Originally Posted by Wotname

Good points SkipperP -

For future reference, in these old Y series, one of the mains is located (pressed) in a carrier behind the flywheel and the other is pressed directly into the crankcase.

Thanks for that info. We will prob be doing a full rebuild so checking the mains is def on the cards.

[skipperpete]

Originally Posted by Wotname

Good points SkipperP -

For future reference, in these old Y series, one of the mains is located (pressed) in a carrier behind the flywheel and the other is pressed directly into the crankcase.

Thanks Wottie, I feared that may be the case. Apparently my latest boat originally had one of these Y series engines and it was replaced with a D1-13 volvo which I’m now replacing with a 2GMF yanmar.

[Compass790]

Yep definitely looking like the full teardown in order. Interesting that skipperpete says mains more exposed to water than big end. He has a lot more experience than I do so if big end journal needs polishing mains certainly will.
Being a horizontal cylinder water past rings may end up on the big end but anyway the salt & oil soup will get pumped around whilst cranking so all need to be polished.

[skipperpete]

G’day Compass790, that bit about wet main bearings was really about vertical inline engines, 2 or more cylinders and that tiny rotational movement is what we hope and pray for on the first inspection. . I’m enjoying reading this thread , lots of interesting info from folks who know this engine and a really helpful and active OP.

[Compass790]

Originally Posted by skipperpete

G’day Compass790, that bit about wet main bearings was really about vertical inline engines, 2 or more cylinders and that tiny rotational movement is what we hope and pray for on the first inspection. . I’m enjoying reading this thread , lots of interesting info from folks who know this engine and a really helpful and active OP.

Cheers skipperpete,
I learn a lot from you & just wanted to get OP onboard with the idea of the full teardown as I'm guessing he's risking his main bearings if he doesnt polish crank journals. One end of the crankshaft oem main bearing is over Au $500 if still available so you dont want to chew them up. That was a few years ago, dont know if you can get aftermarket ones now.
Think its worth the inspection.

I too am enjoying following Op's battle & trying to pass on what I learnt getting our ysm8 sorted.

[Olivia1006]

Originally Posted by Tin Tin

The Yanmar marine engine Facebook page is a very good resource. You can search the pages for all references to your engine, may also be service manuals etc in the files section

Great idea! Thx

[Gregted]

Right. So a short update on the Yanmar.


We ventured out to the yacht today and the ATF and acetone soup was still the same level as when we poured it in a week ago.


If only the exhaust valve and seat was as good a seal as the rusted in rings, I'd be happy but you don't always get what you want.


The great news is that the PTO pulley turns smoothly a quarter turn so the mains should be ok.


Still can't turn the hand crank shaft so gotta pull that cover and funny nut off and have a squiz in there.


We did decide to bring all the bits home so I can put some more time ( and a lot of pressure on that piston ) into the teardown.


The gearbox was clean and had an id in white paint on the inside so it had been replaced at some time. All the gears looked pristine.