Exhaust Leak?

[mikeg205]

Originally Posted by TRBenj

The only thing I would be using silicon for on my boat would be to seal the cupholders!

Permatex RTV has its place inside the engine (intake manifold gaskets, etc), but not on the hull.

Seriously, below the waterline? Thats just a bad idea. You get a leak there and your boat can sink. A marine sealant meant for underwater gear would be the proper thing to use.

Ok TRBenj...your MC-OCD just got a merit increase...

I would only use RTV on those exhaust screws and flanges - okay and maybe for the mature ladies on the pitot screws. Anything else would get a polyurethane or or poly sulfide...

Cool...this is almost like and oil discussion...

[MIskier]

Originally Posted by mikeg205

Ok TRBenj...your MC-OCD just got a merit increase...

I would only use RTV on those exhaust screws and flanges - okay and maybe for the mature ladies on the pitot screws. Anything else would get a polyurethane or or poly sulfide...

Cool...this is almost like and oil discussion...

Mike,

TR knows what he is talking about he is a mechanical engineer by training and does boat restorations as a hobby. What he has said about the sealants is correct, although I would be more in favor of the 3M 4200.

[madcityskier]

5200 is worse, but to take off normal silicone look for a product called De-Solve-It.

[mikeg205]

Originally Posted by MIskier

Mike,

TR knows what he is talking about he is a mechanical engineer by training and does boat restorations as a hobby. What he has said about the sealants is correct, although I would be more in favor of the 3M 4200.

TR mentions underwater gear... I would agree - 4200 for underwater gear as well - underwater gear - prop, rudder assembly, shaft, strut, shaft log.

I will agree 4200 is a better sealant then RTV... however, my chemical engineer friend got into some things with adhesives and sealants that went way over my head. He agreed it's all about work scope, application of product and surface prep - work at Los Alamos.

Anyway, I also have worked on hull repairs at in-laws summer home up in the great white north. RTV has held up and not leaked on us in over 30 years. Is 4200 stronger - I will agree yes.

What is the best way? Okay - 4200 - that enables my MCOCD

[TRBenj]

Im not a MC owner (CC fanatic) and an EE by degree... though I do deal with mechanical stuff at work a fair amount. My recommendations on the sealant are based on practical experience (restored/rebuilt several boats from the hull up). Theyre consistent with the advice I have followed from people much smarter than I am. Silicone just doesnt belong below the waterline.

I use 5200 for pretty much everything now, but Boat Life Caulk works well too. Never used 4200 but Im sure its good stuff based on the other 3m products Ive tried. Ive had to remove running gear that had been installed with 5200 just months before and its not *that bad*. I cant think of any reason you'd need to remove an exhaust port... if you use the proper sealant, you shouldnt have to re-do it in your lifetime.

[lakeoz tristar]

I use 5200 for pretty much everything now, but Boat Life Caulk works well too. Never used 4200 but Im sure its good stuff based on the other 3m products Ive tried. Ive had to remove running gear that had been installed with 5200 just months before and its not *that bad*. I cant think of any reason you'd need to remove an exhaust port... if you use the proper sealant, you shouldn't have to re-do it in your lifetime.[/quote]

http://mastercraft.com/teamtalk/showthread.php?t=51600 POST # 6
is a reason to take it apart and then there's the fact that I am taking them apart right now.. I just like to think ahead and the previous owner had used Silicone and that was not the reason for taking the flanges off so it must have held together pretty good..But I do have some 3-M 4200 and silicone...Guess it will be a game time decision..

[Wake190]

Thanks guys! I certainly did not intent to spark a debate. Sounds like 5200 is the best solution. I'm also going to give the mufflers a thorough inspection. Hope to have a dry bilge this year. Spring can't get here soon enough!

[mikeg205]

5200 maybe a little strong what if you want to get your swag on or maybe go fresh air exhaust... just thinki' ahead

[Lumbergh]

I used black RTV when I replaced my flanges with SS (the old style {94 and older} are NLA in poly 8 screw).

Did a bunch of reading and RTV was recommended a great deal. The idea being that 5200 is TOO permanent. The factory used some sort of clear silicone product.

Bunch of scraping with plastic putty knife and so on to get a clean surface to bolt the new flanges to the hull.

No issues with water leaking from flange area after all of that work.

YMMV.

Old, bad flange: