Mercruiser 470 locked up

[Grady79]

I have a 470 that won't crank and I'm at a loss. I pulled the plugs and tried to crank it and nothing. I put a breaker bar on the crank and it won't even budge. I poured trans fluid into the cylinders and left it sit for about two weeks and still nothing. I'm not sure what else to do. Any help I could get would be great. Thanks in advance.

Trevor

 

[Bt Doctur]

Re: Mercruiser 470 locked up

Is there anything elese we should know on how, why it got locked up.
ran hot
no oil
drive oil missing /lost
severe impact history
etc,etc,etc.

 

[cooter2506]

Re: Mercruiser 470 locked up

Remove the outdrive and see if you acn spin engine. That will tell you if it is the outdrive or engine

 

[Grady79]

Re: Mercruiser 470 locked up

Unfortunately I don't know the history on the boat or the motor. I bought it a couple of weeks ago (not running). I found another 470 but I don't want to purchase it until I find out why this one is seized.

 

[Bt Doctur]

Re: Mercruiser 470 locked up

control box in full fwd, remove rams and 6 mounting nuts and pull drive to isolate the problem

 

[Don S]

Re: Mercruiser 470 locked up

Pull the drive, it may not be the engine.

 

[Don S]

Re: Mercruiser 470 locked up

One other possibility, pull the front pulley off the crankshaft. If the magnets came loose and got wedged in there it would lock the engine up.

 

[Grady79]

Re: Mercruiser 470 locked up

Ok going to try all that now. will be back in an hour or so thanks.

 

[Grady79]

Re: Mercruiser 470 locked up

Got the outdrive off. Tried turning the engine with a breaker bar and it won't budge.

 

[Grady79]

Re: Mercruiser 470 locked up

Took the valve cover off and it looks brand new in there. not a lick of dirty oil.

 

[Don S]

Re: Mercruiser 470 locked up

One other possibility, pull the front pulley off the crankshaft. If the magnets came loose and got wedged in there it would lock the engine up.

.....

 

[Grady79]

Re: Mercruiser 470 locked up

.....

I'm not quite sure how tha comes off. There is one bolt in the pulley of the crank but it seems like it won't unscrew.

 

[Bt Doctur]

Re: Mercruiser 470 locked up

remove the spark plugs and probe with a wooden dowel, wet or rusty would indicate trouble

 

[Grady79]

Re: Mercruiser 470 locked up

I'll have to try probing the cylinders once I figure out how to get the crank pulley off. I think I'll just end up pulling the head to see what they look like. Worst comes to worst I'll buy that other 470 on tuesday. I just want to find out why it won't turn. It wouldn't be the starter stuck against the fly wheel would it?

 

[45Auto]

Re: Mercruiser 470 locked up

Most likely scenario is a piston rusted into a cylinder by a leaking head gasket or a leaking riser/manifold while it sat up for a while. Not a long enough breaker bar in the world to overcome that situation. Lots of times you'll have to break the piston to get it to come out.

Good Luck!

Probably worth your while to look into replacing the manifolds and riser if you're going to the trouble of replacing the engine.

 

[Grady79]

Re: Mercruiser 470 locked up

Most likely scenario is a piston rusted into a cylinder by a leaking head gasket or a leaking riser/manifold while it sat up for a while. Not a long enough breaker bar in the world to overcome that situation. Lots of times you'll have to break the piston to get it to come out.

Good Luck!

Probably worth your while to look into replacing the manifolds and riser if you're going to the trouble of replacing the engine.

That's what I was thinking as well, but at least if that's the case it makes me a little more happy that it was just neglect and not some faulty aspect of the engine.

 

[Grady79]

Re: Mercruiser 470 locked up

Piston rusted fast to the cylinder wall. Pulled the head only to find about a 1/4 inch of rust on the cylinder wall.