Are intake Gaskets same as automotive?

[boatrboy]

On my 7.4 MPI (RWC) I dewinterized and during start up I found my intake gaskets leaking water at the rear of the engine near the distributor. I pulled it all apart today and saw a "GM part number" on the intake gasket. These are the plastic type with a rubber embedded around all the ports.

I never consider using auto parts on the boat, however this item has me thinking that the intake gaskets and the plenum gaskets are the same --- OR --- the wrong ones were in there already.

Does anyone know for sure?

Thanks

 

[fwebster]

Some are, most are different. Mercruiser uses truck blocks with some added features to make the engines more suited for the power needs and rpm range a marine engine operates in. Many engines have heated wet passages where the truck block has none or has a dry passage (depends on year, hp rating, etc.). Unless you know exactly what you are doing, what you save in cost isn't worth the risk of having to do a major repair over again because the gaskets weren't a fit for the application.

I hate the cost, but it is really pretty cheap insurance.

 

[fc3]

Merc does not change the gaskets to a marine grade. So your mild steel head gaskets, for example, are exposed to brine when GM expected that they would only be exposed to protective engine coolant.

Felpro makes a set of marine gaskets for the 7.4 which the machine shop I use recommends. Expensive, but worth it.

Best regards,
Frank

 

[J Levine]

The last time I ordered Merc intake gaskets for one of my BBC's I ended up with a GM part with a Merc sticker on it. I would go aftermarket for these gaskets.

 

[boatrboy]

Thanks for the feedback. I talked with a couple of mechanic friends of mine before getting to read this, and the advice was consistent with the boards. So I went to the auto parts store that stocked the Felpro gaskets, brought mine and compared them in the store. I used a gm truck as the look up. They looked identical so I installed them earlier today and they seemed OK, but I will run it more tomorrow to verify.

Now the problem - my manual says I need the merc scan tool just to time the motor. Anyone know another way??