Mercruiser 5.7 Locked up Tight

[fishingman220]

one day i took my boat to the river and tried to start it and the starter grinded. i thought the batteries were low, and that caused the grinding, new batteries, new starter, and new ringgear for the flywheel. put back together, spun the motor over a few times and then sudden stop, and starter clicked. i stopped and tried to shim starter and looked and the teeth were gone on the flywheel. we pulled the motor yesterday to put new flywheel gear and i pulled the plugs and tried to spin the motor over by hand and couldnt, then with a wrench nothing, and then with 4ft breaker bar and couldnt move it. so now it is on the stand waiting to be broken down. my questions are one, what could have causeed this to lock up. and two, where is a good place to get a good rebuild kit at a decent price????

 

[Bt Doctur]

Re: Mercruiser 5.7 Locked up Tight

could have broken /dropped a valve into a cylinder, pull the valve covers and look to see if there all there..
Broken connecting rod is possable too.

 

[futz]

Re: Mercruiser 5.7 Locked up Tight

could have ingested water, froze up the cylinders, then when you tried to turn it you could have bent the pushrods, twisted a connecting rod, ive seen twisted connecting rods caused bye water in cylinders

see water can't compress, and the force is so overwhelming, the water has nowhere to go.

 

[fishingman220]

Re: Mercruiser 5.7 Locked up Tight

i understand that, but wouldnt it still move alittle bit with all the spark plugs out?

 

[Bt Doctur]

Re: Mercruiser 5.7 Locked up Tight

not if you dropped a valve

 

[jtybt]

Re: Mercruiser 5.7 Locked up Tight

Don't sound good. Just start disassembling.

 

[fishingman220]

Re: Mercruiser 5.7 Locked up Tight

thats what i figured thanks

 

[fishingman220]

Re: Mercruiser 5.7 Locked up Tight

so, update, i pullit part last night, got all the accsesories off, manifolds, wiring, carb, and fresh water cooling system. then took oil pan off and checked rod caps and main caps, all good, not even any fine scratches. a guy i know who does alot of race motors, told me to pullthe timing cover said either a bolt in the gear came out or chain snapped and might be bound up, or a dropped valve. so, tonight i am pulling the top end apart. one question i have is if the cylenders are good, and its just the timing chain or something small like that should i do a rering and berings? or leave it alone tourqe it and put it back together?

 

[Bt Doctur]

Re: Mercruiser 5.7 Locked up Tight

I`m betting on the dropped valve or part thereof

 

[jtybt]

Re: Mercruiser 5.7 Locked up Tight

Yeah, Valve covers are so easy to pull.

 

[futz]

Re: Mercruiser 5.7 Locked up Tight

keep us posted. bottom end good then your halfway there.

 

[FreeBeeTony]

Re: Mercruiser 5.7 Locked up Tight

How did the spark plugs look? When I lost a valve.......the plug in that cilinder was shot.......

 

[fishingman220]

Re: Mercruiser 5.7 Locked up Tight

well got the bad news i was hoping i wouldnt. we pulled the timing cover, looked great, pulled the valve covers, looked good, everything there and clean as a whistle. then pulled the heads and ................ rust in the # 3 and 5 and alittle bit in 1. lots of surface rust on the cylinder walls, pistons, valves, and heads. we sprayed down with pb blaster and it all cames off but you could barely feel it still. do you think i can get by with a hone, rering, and bearing? also, where do you think the water came from? the head gaskits where good, no evidence of leaks, the intake water passages are not anywhere near the inside cylinders. the only thing i can think of is manifold, is there anyway to test them?? should i go through the motor or new short block?? trying to keep the whole thing under a grand if possable(i am hoping) if at all posable

 

[AZChapBoat]

Re: Mercruiser 5.7 Locked up Tight

Was the engine running normally the prior to when the grinding noise started? Did it sit for awhile? I recently had a problem where water was leaking back into the engine because the gasket between the exhaust manifold and risers went bad. Luckily caught it pretty quick and the cylinders all look good but I've had to replace both manifolds and one riser (one manifold was actually cracked and the other had too much rust damage). Engine was not running at full rpm which led to searching for the problem, which was the water leaking back in. The month old spark plugs looked like they were 10 years old. Easy way to check for any water is to check the plugs regularly (and replace them every season). Definitely try cleaning it all up, replacing all the gaskets and see what happens. Give everything a good check and make sure there's no cracks in any of the manifolds, risers, etc. where cooling water runs. Also get rid of any rust stains so if you find any down the line, you know there's still a problem and don't confuse it with old rust stains. Good luck!

 

[300sflyer]

Re: Mercruiser 5.7 Locked up Tight

well got the bad news i was hoping i wouldnt. we pulled the timing cover, looked great, pulled the valve covers, looked good, everything there and clean as a whistle. then pulled the heads and ................ rust in the # 3 and 5 and alittle bit in 1. lots of surface rust on the cylinder walls, pistons, valves, and heads. we sprayed down with pb blaster and it all cames off but you could barely feel it still. do you think i can get by with a hone, rering, and bearing? also, where do you think the water came from? the head gaskits where good, no evidence of leaks, the intake water passages are not anywhere near the inside cylinders. the only thing i can think of is manifold, is there anyway to test them?? should i go through the motor or new short block?? trying to keep the whole thing under a grand if possable(i am hoping) if at all posable

Pour a bit of transmission fluid into each rusted cylinder, and let it sit for a day or two. Then see if you can turn the engine over by hand. You might get lucky. Check to see if there is any water in the oil pan too. Some likely slipped by the rings when it was sitting.

Sounds like your exhaust manifolds and / or risers were leaking... I would suggest replacing them with new ones.

 

[fishingman220]

Re: Mercruiser 5.7 Locked up Tight

yes the motor ran perfect the last time we took it out. then sat for maybe 2 weeks when the grinding started and maybe 2months ago from now since the last time the motor ran. no water in oil in pan. i will take pictures, but i think i will be able to hone cylinders and re ring the pistons

 

[fishingman220]

Re: Mercruiser 5.7 Locked up Tight

tore the bottom end apart tonight, and everything looked great, all the rod and crank bearings, cam and bearings, the only thing i am concerned about is one cylinder has some very very light pitting from the rust in the cylinder. i am wondering if it will come out in a hone job so i can just re ring and bearing it.

 

[Polar_Bus]

Re: Mercruiser 5.7 Locked up Tight

Water got into those LH bank cylinders somehow.....

On ocassion SBC heads will crack between the intake and exhaust valve allowing water into the cyl..... but this is more rare

Sounds like Either a blow head gasket, or manifold water ingestion...

 

[fishingman220]

Re: Mercruiser 5.7 Locked up Tight

i inspected the head gaskets and they were good, looked like the 3 and 5 were almost blown between, but where of any water comming in, and inside the head on the exhaust valves and ports have rust in them so i am almost positive it was the manifold