are orirignal GM pistons for a 454 the same as mercruiser?

[PicoPico]

I need to buy only one piston to replace a damage one for my 7.4 MPI Mercruiser, as this is a 454 GM engine, can use the GM piston instead the mercruiser as the difference in price is huge?

 

[Summer Fun II]

OOPS, I posted in the wrong forum.

 

[AKBASSKING]

Should be OK if they are the same, meaning compression in the cylinder.

 

[scoflaw]

Piston pin height, cc's of the dome, material its made out of that would affect its weight are all very important aspects of a piston. Might not be worth trying to save a couple of bucks.

 

[Ten Years Gone]

Pico, there is no such thing as a Mercruiser piston. It is a GM engine, period. And there are only 3 or 4 piston manufacturers in America. GM contracts out those parts, as well as others. I would suggest you get a second opinion on replacing just one piston. You may find that putting a band aid on a bullet wound is false economy. Depending on what actually transpired to cause such a need for piston replacement, other collateral damage may have already occurred to the engine internals. This will require a professional rebuild in any event. Do not mess around with a rotating assembly if you don't understand the complexities of how the system of moving parts must be in balance to avoid the engine grenading itself. If you need further explanation, PM me. I would be glad to help you through your dilemma.

 

[AKBASSKING]

Pico, there is no such thing as a Mercruiser piston. It is a GM engine, period. And there are only 3 or 4 piston manufacturers in America. GM contracts out those parts, as well as others. I would suggest you get a second opinion on replacing just one piston. You may find that putting a band aid on a bullet wound is false economy. Depending on what actually transpired to cause such a need for piston replacement, other collateral damage may have already occurred to the engine internals. This will require a professional rebuild in any event. Do not mess around with a rotating assembly if you don't understand the complexities of how the system of moving parts must be in balance to avoid the engine grenading itself. If you need further explanation, PM me. I would be glad to help you through your dilemma.

Very good point.

 

[PicoPico]

Thanks my friend very good explanation, after making hundreds of calls I found a standard piston (used in perfect shape) from the same mercruiser engine the problem was definetly the pin, so we replaced both the pin and the piston as well as all the bearing, we left all the original rings to keep it original. it transpired that the reason for the pin to fail, was that water got in the engine some time ago when some gaskets and seals were replaced. Engine has now been put together and tested this weekend, everything went well, oil pressure, compression, tempeture, etc, only a small water leak at the back in one of the hoses of the steering oil cooler, but fixed!

Pico, there is no such thing as a Mercruiser piston. It is a GM engine, period. And there are only 3 or 4 piston manufacturers in America. GM contracts out those parts, as well as others. I would suggest you get a second opinion on replacing just one piston. You may find that putting a band aid on a bullet wound is false economy. Depending on what actually transpired to cause such a need for piston replacement, other collateral damage may have already occurred to the engine internals. This will require a professional rebuild in any event. Do not mess around with a rotating assembly if you don't understand the complexities of how the system of moving parts must be in balance to avoid the engine grenading itself. If you need further explanation, PM me. I would be glad to help you through your dilemma.