Hi From Down Under

[Wotname]

Originally Posted by Gregted

........
Also found some pics of cylinder removal tools. Prices range from next to nothing homemade, to over $2000.

Have a look at post #42 in the thread https://www.cruisersforum.com/forums...-280728-3.html

The whole thread may be of interest to you.

[Compass790]

Gregted the the clearance between the face of the oil pump rotor & the sealing cover is the one that can be problematic most commonly. Seems to give more trouble on the 8hp than the 12hp so you may be lucky .Reason for that is higher revs on 8hp so faster wear I suspect.
I machined new crank main bearings to avoid Yanmar price but you may not need them.

[Gregted]

Rightio,


So we took the head off the Yanmar yesterday and I cleaned it up today.


The exhaust valve was stuck open, so no chance of it starting as it was.


The exhaust port is pretty much pitted beyond repair as is the exhaust valve.


I might still work on it with some wet and dry but I don't like our chances of getting any compression, but never say never, right?


Apart from all that, It all cleaned up ok. The water drain plug and the block drain port were that clogged, I thought it was solid cast but knew it couldn't be so I hacked at it and low and behold, the crud came out and it is now clear, so pretty sure it hasn't been drained for a millennia.



Couldn't get the piston in the motor to move yet but bought some Freeze and Release so I will head back out in the next day or so and try and freeze the piston to break the rust seal.


Tried to put it in gear and turn the prop shaft but that did nothing to the piston so you can't push start a diesel inboard. Who knew, right??

[Adelie]

Welcome to CruisersForum!

I would suggest updating your profile with your general location and your boat make & model or “Looking” in the "Boat" category. This info shows up under your UserName in every post in the web view. Many questions are boat and/or location dependent and having these tidbits under your UserName saves answering those questions repeatedly. If you need help setting up your profile then click on this link: https://www.cruisersforum.com/forums...ml#post3308797

I would happily help more if the link above is not enough.

[Compass790]

Okay Gregted,
Yep as suspected you have the classic exhaust elbow failure allowing water into the cylinder causing a multitude of problems. You would be surprised at how bad they can be & still be repaired enough to run quite well. Dunno if you have seen any Aussie 50 vids on youtube but he is worth a look. You can get a new aftermarket head or a good used one if you cannot get that to a useable state.The valve seats can still seal pitted as long as they are not pitted across the wdth of the seat. Depends on how cheap you want to do the rebuild.
I would try using your old valve in an electric drill with coarse grinding paste on that exh v/v seat for a start & see what it looks like after a good grinding.
I shall attempt to attach a pic of an ysm8 head valve seats that work perfectly ok though pitted.
Another option is to look for another used ysm12. I'm pretty sure the yse12 & the ysb12 have the same cylinder heads.
You should be able to get a non running example for $300 but obviously I dont know how many are around your area.I think its a good idea to get a used engine for parts if you intend to keep the boat a long time.
They aren't common here.
If you need help locating a new cylinder head pm me.

[Gregted]

Originally Posted by Compass790

Okay Gregted,
Yep as suspected you have the classic exhaust elbow failure allowing water into the cylinder causing a multitude of problems. You would be surprised at how bad they can be & still be repaired enough to run quite well. Dunno if you have seen any Aussie 50 vids on youtube but he is worth a look. You can get a new aftermarket head or a good used one if you cannot get that to a useable state.The valve seats can still seal pitted as long as they are not pitted across the wdth of the seat. Depends on how cheap you want to do the rebuild.
I would try using your old valve in an electric drill with coarse grinding paste on that exh v/v seat for a start & see what it looks like after a good grinding.
I shall attempt to attach a pic of an ysm8 head valve seats that work perfectly ok though pitted.
Another option is to look for another used ysm12. I'm pretty sure the yse12 & the ysb12 have the same cylinder heads.
You should be able to get a non running example for $300 but obviously I dont know how many are around your area.I think its a good idea to get a used engine for parts if you intend to keep the boat a long time.
They aren't common here.
If you need help locating a new cylinder head pm me.

Thanks Compass790 for the reply.

The mixing elbow was pretty clear so I sprayed some WD40 in the water inlet and it didn't seem to run out the engine side of the elbow but did run out the exhaust side so I thought the inner water channel might be intact.

The piston head and sleeve look really good so I was wondering if the rust might be the result of salt water condensation more than cooling channel water. It is pretty badly pitted though, so you're probably on the money.

I'll pour some more water through it when we get back to the yacht and see where it runs.

Also found a local small engine machine shop mechanic who will grind a new exhaust seat for $60 and insert and grind a new one for $100 if the old one is beyond grinding.

I have watched some of Aussie50 videos and he has resurrected some pretty beaten up old engines.

Also just watched a vid of a Yanmar 8 that had been sitting in a back shed for over 20 years and the new owner got is started and running after bleeding the fuel lines and kicking it over on some kerosene.

I will def get in contact for a new head if this one is fubar.

If we can't free up the piston as is, I think I will disconnect the prop shaft and tip the Yanmar on its side so we can soak the piston in some Acetone and ATF for a time. The horizontal piston makes it hard to let it soak.

I watched a vid of a bloke using coarse dry sandpaper on a valve seat and it seem to clean up nicely, so last night I tried it and it made a difference but not a huge one so machining/cutting might be necessary.

If we get it turning over, we might just reassemble the motor and see what happens.

[Wotname]

Whereabout is the piston sitting in the cylinder?

Near TDC, near BDC or somewhere in the middle.

[Gregted]

Originally Posted by Wotname

Whereabout is the piston sitting in the cylinder?

Near TDC, near BDC or somewhere in the middle.

Hey Wotname.

I measured the visible bore at 70mm and the stroke should be 90, so just off bottom, I guess.

If we can't free it up as is, and we tip it on it's side, I might remove the pan and try to tap it up the bore.

Don't really want to mark the bore with a broken ring or rust but we'll see.

[Wotname]

Originally Posted by Gregted

Hey Wotname.

I measured the visible bore at 70mm and the stroke should be 90, so just off bottom, I guess.

If we can't free it up as is, and we tip it on it's side, I might remove the pan and try to tap it up the bore.

Don't really want to mark the bore with a broken ring or rust but we'll see.

No need to tip it on its side.

Remove the crankcase cover on the LHS on engine (viewed from the flywheel) and you should be able to see the conrod bolts and remove the conrod cap. This cover is the equivalent of a pan on a vertical engine but way easier to access.

Insert a suitably sized piece of timber against one face of the conrod and apply the hammer! Flood the cylinder side with anything like WD40 or any thin oil.

It may break a ring or at the worse, a piston land - neither is a big deal in the large scheme of things. It may just break the rust seal.

[Gregted]

Originally Posted by Wotname

No need to tip it on its side.

Remove the crankcase cover on the LHS on engine (viewed from the flywheel) and you should be able to see the conrod bolts and remove the conrod cap. This cover is the equivalent of a pan on a vertical engine but way easier to access.

Insert a suitably sized piece of timber against one face of the conrod and apply the hammer! Flood the cylinder side with anything like WD40 or any thin oil.

It may break a ring or at the worse, a piston land - neither is a big deal in the large scheme of things. It may just break the rust seal.

Hitting up from the bottom/port side would be my next step before tipping it over. I can hammer a block of wood from the head/starboard side but so far it won't budge.

Have tried a jack onto the wood above the piston against the seat opposite but the engine mounts gave too much to allow me to apply too much pressure.

Hoping freeze and release to the piston will crack the rust seal or I might also apply some butane torch heat on the sleeve and freeze the piston as well.

Disconnecting the prop shaft and tipping it over is a last resort. I can flood the combustion chamber if I reinstall the head but can only fill it to the height of the injector unless i fit a hose to the injector port to raise the height above the motor height.

Then I still have the problem of the valves not sealing watertight and the ATF leaking out past the valves so on it's side would have the piston upright and negate all that.

Still, hope we don't get to that.

[Wotname]

You could silicone a piece of plywood etc against the block in lieu of the head with a bit of tube siliconed into the wood in which to feed in lubricant of your choice (say diesel /ATF&Acetone etc) to flood the cylinder.

I THINK that once you have removed the conrod cap, the piston will drive out OK with a good whack, especially if the cylinder has been flooded with lubricant.

Looking forward to hearing how it goes.

[Gregted]

Originally Posted by Wotname

You could silicone a piece of plywood etc against the block in lieu of the head with a bit of tube siliconed into the wood in which to feed in lubricant of your choice (say diesel /ATF&Acetone etc) to flood the cylinder.

I THINK that once you have removed the conrod cap, the piston will drive out OK with a good whack, especially if the cylinder has been flooded with lubricant.

Looking forward to hearing how it goes.

Hadn't thought of the plywood cover idea. That will be added to the list of solutions before any tipping goes on.

Access and room to swing a hammer at the conrod end/port is about as limited as the head/starboard. I was also very conscious of the proximity of my hammer blows to the head bolt threads. Don't want to add removal and installation of new head bolts to the bills.

I cut some circles out of thick junk pine to hammer on at the starboard side and wailed on that as much as room allowed but no joy. The pine absorbed much of the impact so might have to cut some hardwood and try again.

Also thought about making a pusher like a wheel puller across the head bolts and a large piece of all thread in the center to push the piston down. That would allow me to put significant force on a block of wood on the piston. Aka a bush press.


Attached pic is of the cylinder liner puller but place the nut on the other side of the cross bar and crank down instead of up and it becomes a pusher.

[Compass790]

Ok Gregted,
Yes I need to give myself a slap for not mentioning getting a new valve seat installed. That will be a lot cheaper than a new cylinder head.

Very surprised its not the exhaust elbow but yes if no water comes down cylinder head side its ok atm. Be good to test it with garden hose pressure. I would still make another one that cant fail like they do when you get a chance. Maybe it was the owner continually operating the starter motor with no start & water inlet open & flooded the exhaust. That could explain the flooding, you have too much water damage for condensation. I just assumed it would be exhaust elbow failure as that is the most common problem but I'll try & remember flooding engine from no start next time I post with a YS seized engine. Dont forget to check for cracks in the head & block.

You are very lucky that sleeve looks ok.
It sounds like you are thinking through the problems pretty well. I'll be interested to hear how yr improvised screw jack works. .Easier to help people who are mechanically minded

I hear you trying to hamer with engine in situ, especially in Queensland heat.
Looking fwd to hearing you have freed it up.

[Compass790]

Forgot to add be careful heating sleeve as its sealed by o-rings near the bottom & they are over 40 years old assumedly. They seal the crancase from the seawater. I put silicone around the bottom of the new liner where it sits in the block as well when I install as a second line of defense. Not necessary as they go for 40+ years without silicone backup.

[Gregted]

Originally Posted by Compass790

Ok Gregted,
Yes I need to give myself a slap for not mentioning getting a new valve seat installed. That will be a lot cheaper than a new cylinder head.

Very surprised its not the exhaust elbow but yes if no water comes down cylinder head side its ok atm. Be good to test it with garden hose pressure. I would still make another one that cant fail like they do when you get a chance. Maybe it was the owner continually operating the starter motor with no start & water inlet open & flooded the exhaust. That could explain the flooding, you have too much water damage for condensation. I just assumed it would be exhaust elbow failure as that is the most common problem but I'll try & remember flooding engine from no start next time I post with a YS seized engine. Dont forget to check for cracks in the head & block.

You are very lucky that sleeve looks ok.
It sounds like you are thinking through the problems pretty well. I'll be interested to hear how yr improvised screw jack works. .Easier to help people who are mechanically minded

I hear you trying to hamer with engine in situ, especially in Queensland heat.
Looking fwd to hearing you have freed it up.

Just reading your reply and thinking it can't be condensation either or the inlet would be just as bad, so it must be that mixing elbow.

Maybe the rust is that bad that it has grown enough to seal the original leak hole and will probably leak again when it gets hot so I will definitely make a stainless elbow with the water inlet on the exit side.

Had a quick look over the head and block and can't see any cracks but will have a closer look.

You are spot on about those rubber o-rings on the sleeve. I will stay the heating and hope the freeze and release will crack the rust seal.