Yanmar YSE8 seized

[Mobcat]

Hi all new to the scene I have bought my self a new yacht with a seized Yanmar yse8, I don’t know how it’s seized but I suspect over heating but maybe not ? I suspect over heating because the water pump">raw water pump was seized but that may of occurred after the seizure, anyway I have tried all the usual to no avail breaker bar on crankshaft trying to rattle it with the starter motor with injector out and no movemeto of the piston ….. bottom end seems fine no water in oil etc ….. so I removed the head and what I discovered was a corroded mess in the cylinder head actually seems ok, but I still can’t get her to turn once I have removed all the gunk and sprayed WD40 in it over night repeatedly….. what’s next crew any ideas …. As usual cash is tight bla bla bla otherwise I would have a super yacht with a crew and wouldn’t be here
Thanks in advance

[Wotname]

Welcome aboard CF, Mobcat.

Well the good news is the YSE8 is an old work horse and mostly very repairable by anyone half proficient with mechanical tools.
After market sleeve, piston, head gasket and rings are available at fairly reasonable prices or at least they were a couple of years ago.

You can remove the cover opposite the head and remove the cap on the big end of the conrod. This may allow you bash the piston out using a hardwood drift and decent hammer. All depends on what access you have in the 'engine room'.

Once the piston is out, the sleeve can be removed with the engine in situ. Fit a new sleeve, piston (if needed) and new rings and you might be good to go.

Before sending too much money though, check the wear in the oil pump as the oil pump is high wear item in these engines and although fixable, they can chew up the budget. The specs are in the manual and it is not hard to check the wear.

There should be a service manual in the CF library but I can send you one if not. The YSM service manual is also very handy as it contains more detail and at least 80+% of the YSE is interchangeable with the YSM.

[LittleWing77]

Wottie is King and his advice is golden!

I would only add that the link below is a recent thread about a seized yanmar 3GM (injection pump was thought to be the culprit); it has numerous ideas for yanmar troubleshooting as well as seized-engine fixes.

Advice sought. Engine Seized after Installing Injection Pump
https://www.cruisersforum.com/forums...mp-254051.html

Have you thought of trying penetrating oil instead of WD40...?

[Wotname]

Forgot to say, if the piston is resisting a 'reasonable' tap of the hammer, you can try more extreme ways of freeing up the rings. Remove the oil and completely fill the crankcase with diesel. Let it sit for a few days, drain and try removing the piston again.

The idea is to have the diesel penetrate the rings from the crankcase side.

[GordMay]

Greetings and welcome aboard the CF, Mobcat.


Automatic Transmission Fluid, Brake Fluid, & Acetone:

Brake fluids are blends of several components, such as vegetable oils, various alcohol-based fluids, and synthetic ester base oils, diluents, and one or more oxidation and corrosion inhibitors.
Mix it 50/50 with a synthetic Automatic Transmission Fluid [ATF], like DexronVI, and you have yourself a general purpose penetrating fluid [& good surfactant].

Acetone can also be used, in combination with ATF [or /w brake fluid], to create an effective penetrating oil.

[rotrax]

To turn a siezed engine like yours I would use a 50/50 mix of ATF and Acetone around the piston.I would then place a piece of lead on top of the piston - perhaps a 1/4 inch thick - put the head on and tighten it down. This should press the piston downwards. Once it is moving or has moved a thicker piece of lead - or hardwood - can be used to keep it going.


Harley Davidson Evo engine manuals say thread a piece of cord into a cylinder coming up to compression through a spark plug hole - valves closed - and then it is possible to undo the crankshaft nuts. The cord cannot be compressed and so stops the engine turning without damage.


I was a Veteran - pre 1914 - Vintage - pre 1930 - and Classic motorcycle dealer and restorer. I am very familiar with the type of job you are dealing with. Using the cylinder head as a press does work. I have direct experience of this method being successful. The ATF / Acetone mix is essential. The best penetrating medium I have ever used.

[Compass790]

Welcome to the forum mobcat,
I venture to suggest yr exhaust elbow is knackered as it's the most common cause of water getting in the top end. I sell aftermarket parts for ys8/12 series Yammers so have a fair handle on their failure points as does Wottie. You can still get parts but i wouldnt bother rebuilding if you have to buy from a Yanmar dealer. If you search for ysm8 in this forum our rebuild story might have some useful info for you. i'd make a new mixing elbow out of sched 10 316l ss which you can stick weld.
They are noisy shakey beasts but are long lasting & very reliable with a little care.
Where in the world are u mobcat?

[Wotname]

One difficulty with using any type of penetrating fluid on the YSE rings is getting the fluid anywhere near the rings - gravity works against you with an horizontal cylinder!

Another 'trick' is to remove the pushrods so both the valves are shut, refit the head with the injector removed and fit the combustion chamber with the penetrating fluid of choice via the injector hole. Keep topping it up!

I completely concur with rotrax's choice of 50/50 mix of ATF and Acetone.

[Compass790]

Mobcat after looking at your pic I'm not so sure its a leaking mixing elbow, looks more like leaking head gasket which could well have been caused by overheating. All the salt crystals lying on the block point to the head gasket assuming the elbow wasnt leaking outside. Leaking head gaskets is not an uncommon problem on these engines either. I find if you put a thin smear of 518 or 515 Loctite on both sides of the head gasket when installing you get no grief but if you put on dry it's not a certain outcome. 518 is not cheap but I'd try any gasket cement rather than putting on dry.
If the bore isnt too pitted or over dia spec you might be able to get away with just a set of new rings.
Good luck with freeing it up & please let us know how you get on.

[Halifax Sailor]

Mobcat:

Listen to wottie and Compass. I have a 1978 ysb8 and they have helped me so much in the last couple of years. They know their stuff!!

[Jimlahey]

Have the same problem with a seized piston. Got it out with a block of wood. Liner and piston not serviceable. I'm after a piston, liner, head gasket, big end bearing std and gaskets anyone know of anywhere in australia to get these? I'm in Victoria. Any help would be greatly appreciated

[NevilleCat]

I guess you probably have tried Mariner Engineering in Newport?

[Jimlahey]

Yeah awaiting availability and price. A user named compass said he can source aftermarket parts. Hopefully he sees this thread again

[Compass790]

I will pm you re parts

[Jimlahey]

Thanks mate