Great new sealant

[witenite0560]

I was putting my lower end back on and needed the big rubber gasket that goes between the lower unit and the inner exhaust housing (1970 115hp Evinrude). Unfortunately, my boat guy didn't have one. But, he told me to go to the Auto parts store and get some stuff called Great Stuff gasket maker. He said he loves it! So, I did and it seems to be.... well, Great Stuff! It comes in a aerosol can with a plastic screw on tip and costs about $15. It says on the can that it will make 8 - 10 standard 4 cylinder valve cover gaskets. So, should make about the same number of lower end/exhaust housing gaskets. I was a bit concerned with how it would hold up to exhaust temp. But, it's good up to 500 degrees and the boat guy said it's worked great for him. It has about a 5 minute working time, so you want to put it on just before you assemble.
One word of caution, I'd be careful about using it where it might squeeze out to the inside of oil wetted or coolant systems. Use sparingly in those situations, so you don't end up with a lot that squeezes out and could potentially come loose and block passages and such.

Oops, my bad, it's called "Right Stuff", not Great Stuff. Sorry.

 

[Cofe]

Re: Great new sealant

I haven't used that aerosol yet, but for exhaust gaskets I would be wary. For water gaskets blue rtv works well, but you have to smear it on thinly with you're finger.....real thin. I have used it in combination with gaskets to seal water and oil on damaged gasket areas. Dow/Corning makes a red 736 silicone that withstands 700 degrees. I have used it on hot applications but not exhaust stuff. Gaskets for exhaust in the long run, is what i suggest.

 

[witenite0560]

Re: Great new sealant

Yep, I've used blue rtv a lot on gaskets, too. You're right, put it on very thin. One of my pet peeves is people who gunk it on. I just overhauled a 6 cyl engine that likely failed due to someone gunking RTV on thick and pieces of it blocking oil passages. The #1 connecting rod bearing cooked and eventually the cap bolts failed.
I agree, I have my reservations about this stuff. But, the guy who recommended it is the local Johnson/Evinrude expert, so I'm giving it a try. Besides, I figured the OEM gasket is just black rubber, so this stuff should do as well. It appears to be designed to be thick and fill gaps to some extent. I also use the orange on high heat areas. First place I ever saw it was in the engine bays of F-4 Phantoms! Talk about a high heat area! LOL The engine bays were full of the stuff. It was used for everything from gaskets to just fill in spaces where you didn't want stuff to be able to lodge or hide or places you didn't want things to chafe. Good stuff!

 

[Cofe]

Re: Great new sealant

Hey witenight great post... Who makes the orange rtv? I have used lots of red by locktite and dow/corning, but I have never seen orange. Must be great hot stuff if used on jet engines.

 

[witenite0560]

Re: Great new sealant

Permatex makes the orange stuff I have. I guess it comes in a red tube. But, the sealant itself is orange, at least to my eye.