Mercruiser 260 V-8 Starts, Idles, then siezes at normal to high RPM

[Lubeboy]

Sorry, if repost of similar problem

Engine starts right up.

Idles okay, for as long as you want.

As soon as I try to raise RPM, it will give sieze like stop (very agressive stop). Problem is we can just keep doing this. It will start back up and give same problem.

Any hints on what could be wrong? Assuming if bad piston, rings, bearings, it would not let me restart so easy?

thanks.

 

[JustJason]

Re: Mercruiser 260 V-8 Starts, Idles, then siezes at normal to high RPM

so whats locking it up... have you pulled the plugs to see if you got water out of them (you usually would not on a hi rpm sieze). Any water in the oil?
Pull the drive unit and run the engine on a garden hose straight into the thermostat housing and see if its the drive thats doing it. Its probably an alpha 1 in which case you can pop the top cap and have a look at the upper gears anyways.

 

[Lubeboy]

Re: Mercruiser 260 V-8 Starts, Idles, then siezes at normal to high RPM

The engine locks up... no water in oil, have not checked plugs, will do.

Pulling drive? Do I really need to do based on engine lock up? Getting plenty of water shooting out of exhaust.

thanks for help.

 

[Bt Doctur]

Re: Mercruiser 260 V-8 Starts, Idles, then siezes at normal to high RPM

The outdrive shafts turn with the engine ,so a drive locking up would stop the engine.

 

[jtybt]

Re: Mercruiser 260 V-8 Starts, Idles, then siezes at normal to high RPM

...but I think at any RPM above 2000, it would shear the teeth. Besides, what would cause the gears to lock up the engine over and over.

Sounds like hydrolocking right at the top of the compression stroke from the minimalest amount of water getting by a bad gasket or warped head.

Hard to diagnosis this one without inspecting.


One thing, don't continuing running. It can only get worse.

 

[Lubeboy]

Re: Mercruiser 260 V-8 Starts, Idles, then siezes at normal to high RPM

okay, checked out plugs and cylinders, found no water, but surprise, surprise, found one cylinder with no compression... consistent over 120 on all except one with less than 25... probably the problem... siezes when rpm up, but can restart with other 7 cylinders, till I try to get rpm up again.

shutting her down for now... trying to figure out how to rebuild. lol

 

[Don S]

Re: Mercruiser 260 V-8 Starts, Idles, then siezes at normal to high RPM

Engine starts right up.

Idles okay, for as long as you want.

I'm sorry, but if you have a cylinder with 0 compression, it does not idle OK. You have a dead miss.

Pull the head.

 

[Lubeboy]

Re: Mercruiser 260 V-8 Starts, Idles, then siezes at normal to high RPM

Thanks all for help... did inspection of outdrive today... no oil and gears broken... long story short, it was the outdrive causing lock-up... getting new one.

Now working on one cylinder with no compression...