170, perpetual riser gasket leak

[nola mike]

Leaking AGAIN from the reservoir/manifold gasket. This is an almost yearly occurrence. I've tried OEM, and I think every aftermarket brand. Tried with and without gasket sealant. I stripped out another bolt on the manifold today, and replacing it with a helicoil was an adventure (the bolt hole is shallow). Anyway, noticed that the replacement gasket has 2 slots in it, where the manual shows a gasket with one slot. Since the other slot dead ends on the reservoir, I didn't think that that was the problem, but now I'm not sure. I've had the manifold resurfaced, and though the reservoir is now a few years old, it leaked after the first season. Any other 470 guys have this problem? Am I using the wrong gasket? It always leaks around the aft 2 bolts (which is where that rogue slot in the gasket is)

 

[stonyloam]

Aluminum or cast manifold?

 

[nola mike]

Aluminum

 

[stonyloam]

sounds like you have the correct gasket. this one right? http://www.mercruiserparts.com/showSpecialPicture.asp?pn=18272

 

[nola mike]

Yeah. If you look in the manual though, the choice is either a 3 gasket sandwich or a gasket with one slot. Manual says slot should face forward.

 

[stonyloam]

Yeah this gasket supersedes. The old sandwich setup.

 

[nola mike]

See how the one in the manual has only one slot though? Anyway, so far so good. 35 mile trip for lunch (without the kids!), ran great. No more exhaust leak, shifted OK but not perfect, no coolant loss, and it seems that the water in the gas tank is finally gone.

 

[Eric 3.7LX Alpha 1]

Nice glad to hear she's running well for you!

 

[nola mike]

Well, that didn't last long. The threads in one of the holes was a little rough, don't know if that had anything to do with it, maybe it didn't torque correctly. No thread chasers here, trying to decide whether to run it as is for another couple of weeks, or try another repair until I can get some. Next plan is screw the gasket and use a high temp rtv. When I can I'm goingto thoroughly clean the threads and get new bolts. Suggestions welcome, I'm going crazy. Here's where the 470 is bad news. I'd love to get a new manifold and reservoir and be done with it. Also, screw the exhaust leak. I'm not taking the manifold off again.

 

[nola mike]

RTV was a spectacular failure. I was afraid after I put it together that the RTV would block the coolant passages when squished together. Although I never overheated, the leak persisted. When I took it back apart there was gasket material in a couple of passages. Cleaned out, new OEM gasket in hand. Chased threads, bolts, will try to install the gasket nekkid this weekend and see how we do.