Mercruiser V8 seized?

[sylvana]

Have recently bought a power boat with a 250HP 5.7 V8 Mercruiser - year 2001.
Engine has very low hours but has been left sitting for a couple of years.
When trying to start it there is a loud clunk as starter motor engages but doesn't seem able to turn the engine. I'm thinking of removing plugs and pouring some oil down and then perhaps trying to somehow turn the engine over by hand.
Any suggestions would be very welcome.......................

 

[Cliveshep]

Plugs out, some diesel in the cylinders, leave for a week or so, get large wrench on crankshaft nut and lever it over. If it moves fine, turn it a few times that way then try the starter without plugs in.

If you need a bit more "welly", buy one of these chain wrenches and clamp it around the crankshaft pulley, by flipping it over you can increase any gradual movement up/down/back/forwards until you get it loose. Trying to reverse the wrench on the cranklshaft nut will undo the nut, a chain wrench on the pully which is keyed will not. The top edges of the pulley do not interract with the drive belts to the pump/alternator and any burrs you make can be filed-off later.

Suitable chain wrench here: http://shop.ebay.co.uk/i.html?_kw=S...aterials_Plumbing_MJ&_trksid=p3286.m104.l1198

 

[MapisM]

Plugs out, some diesel in the cylinders...

Why not oil as the OP mentioned?
Btw, also the recommended mixture for the fogging of these engines is 50/50 gasoline and 2 stroke oil.

PS for sylvana: don't take me wrong, I'm just curious (and apologies if that hurts), but! ...did you buy the boat without even checking if the engine was running?

 

[Sandyman]

I dont know this engine so please ignore my comments if irrelevant.

Are you sure the starter motor is engaging ??? Could the clunk you hear just be the pre- engaged starter operating ?? or bendix ??? In which case it could just be the starter motor jammed. Hope that helps.

 

[sylvana]

mercruiser v8

Thanks a million for your responses,will take the advice and see how we go.In response to your question,yes I did know the engine may not run but this is all part of the challenge!I allowed for this when buying the boat.

 

[MapisM]

I did know the engine may not run but this is all part of the challenge!I allowed for this when buying the boat.

Aha, fairenuff.
In this case, it would have been a good idea to turn it manually as Cliveship suggested, before trying to start it...
...though I'm afraid this is not a very useful suggestion anymore!

 

[Cliveshep]

Aha, fairenuff.
In this case, it would have been a good idea to turn it manually as Cliveship suggested, before trying to start it...
...though I'm afraid this is not a very useful suggestion anymore!

CliveSHEP not ship!

Your earlier response - diesel will find it's way down the rings a lot quicker and easier than oil will, and it's probably a rust film locking the pistons that is holding the lump from turning over. An oil mix is good to STOP your engine seizing, that particular horse, however, has already bolted out the door so closing the door behind it won't help.

 

[carlton]

Have you checked the starter solenoid(s)?

 

[MapisM]

CliveSHEP not ship!

Whoops, apologies. My mind must have translated into what seemed more appropriate for a boating forum...
Point taken re. diesel vs. oil.

 

[gordmac]

Other option is a paraffin and oil mix. Watch it doesn't have sticking valves, you can bend them if you are a bit "enthusiastic".