Crankcase Sealant.-

[Sea Rider]

Was wondering if it would be proper to use Mega Gray Silicon to seal both crank case halves as opposed to Loctite 518 which is what Tohatsu factory uses on 2 strokes portable engines for a good seal.

Happy Boating

 

[Faztbullet]

Nope as it will wash out....

 

[wrench 3]

Loctite 518 is an anaerobic sealer (it sets up when air is taken away from it) as opposed to silicone sealer that needs air to setup.

 

[Sea Rider]

OK, its for sealing a small 5 HP OB engine, when silicone is applied to both mating surfaces and torqued to specs, assume silicone will form a good gasket once cured, right ? How can silicone be washed. Mega Gray is used to form gaskets. Usually apply a thin coat on both sides of thermo gaskets and once removed after months of use it's still there intact.

Happy Boating

 

[racerone]

????----You need to understand that an outboard crankcase joint is a precision joint !----What this means is that it is a metal to metal joint for proper bearing fit / clamp-up.---Some sealers have too much filler and will not squeeze out properly.--Use only the proper stuff and not what you think is " good enuff or better " for this application...-----BRP " gel seal " or loctite 518 are used on outboard crankcase joints !!!

 

[Sea Rider]

Well it's not a I think issue, was just asking due to having seen many OB engines just sealed with silicone. If will have issues or not in the short run it's their problem, Now have the overall tech information and how crankcase sealers work, thanks.

Happy Boating

 

[Faztbullet]

Silicon no matter whats the usage states will turn soft/goooey and slick in the constant presence of fuel. This and crankcase pressure will cause mating surfaces to "wash out". Try to seal a fuel sender on a fuel tank and you will see the same think happen. On some older outboards you could have gotten away with it as they used a o-ring spaggitti seal the length of crankcase

 

[Frank Acampora]

Crank case halves are a precision joint. SO precise that in may cases the sealer is redundant--they will seal without anything. For my engines I use whatever is handy at the time. I never have any problems. .When rebuilding an engine for a customer I spend the 14 or 18 bucks and get the manufacturer recommended sealant-- it is a question of good workmanship.