MCM 120 Mercarb Question

[BillysBoat1986]

Hi everyone! I just got a rebuild kit for my 2.5, 120 hp, carburetor PN: 13898490. It has a lot of gaskets, but I have an old rotted out gasket that's at least 1/4 inch thick that mates the carb to the engine. Does anyone know the PN to that gasket or where I can find it in the manual? I need a new one.Thanks a bunch!

 

[hemi rt]

It's not a gasket but an insulator to keep the heat from the manifold away from the carb. There should be a gasket glued to each side of it; if not you can carefully scrap the old gaskets off and use the 2 that should be supplied in the kit. The better kits usually have this insulator. If it's in bad shape you could take it to a car dealer ship and match it up to a car one.

 

[BillysBoat1986]

A dealership would have a part from an engine that was never used on any car and made in the mid eighties? Sounds like a long shot.

 

[thumpar]

A dealership would have a part from an engine that was never used on any car and made in the mid eighties? Sounds like a long shot.

The 120 2.5l was used in a car. It was the mid 60's Nova. The 3.0l was never used in a car.

 

[BillysBoat1986]

Awesome! I didn't know that. Thanks for the info. You all really teach me a lot.

 

[Fishermark]

You mention having a Mercarb. These engines either came with a Mercarb or a Rochester - they are very similar. BUT, if memory serves, (and it may not!), the bases are slightly different and not interchangeable.

 

[BillysBoat1986]

I have looked everywhere for this insulator and can't find a new one. I'm going to make one. Does anyone have any ideas what I can use for stock? It has to withstand high temps.
Thanks a bunch!

 

[BillysBoat1986]

Hi Fishermark! I have a Mercarb. I spent a lot of time rebuilding it. I used the Mercruiser manual and you tube. I'm debating on using 8802 b 1/2 sealing compound on the old insulator. It is used on aircraft extensively and is heat resistant. Only problem is it dries hard as a rock and is hard to remove. I have no doubts though this stuff will seal the carb to the manifold without any leaks. Any thoughts?

 

[Fishermark]

I personally would not use a sealer between the carb and the manifold.

 

[NHGuy]

Either order the exact gaskets or make some.
To make them.
Get some gasket material sheets at the auto parts store. Then you'll need to experiment a little. I'd use some padded clamps to hold the gasket between the spacer and a piece of wood. Not too tight though, don't want to distort or break the spacer.
Once clamped, cut the gasket with a razor knife. Or mark it and then cut it afterward.

 

[BillysBoat1986]

I want ahead and just used the gasket that came with the rebuild kit and removed the 1/4" spacer. When I installed the carb I had to add extra washers to the mount nuts so that the carb would have a good seal to the engine. Ran it up this weekend on the river for several hours and everything is working nicely. It was a really hot 90 degree plus weekend too. Thanks everyone for your help.