RTV on a crank case flange?

[billw]

I am resurrecting a Force 15, which is basically a Chrysler with different paint and decals. I was surprised to see black RTV used as crank case sealant and even MORE surprised to find that is what is called for in the factory service manual. I wonder why? I am thinking of using red, anaerobic sealant but I am wondering whether I will be sorry….Thoughts appreciated.

By the way, it sure was a lot easier to clean it off….kind of nice!

Long live American manufacturing!

• This topic was modified 4 years ago by billw.

[fleetwin]

Well, I usually go by manufacturer’s recommendations, but would never use RTV on OMC crankcases for sure. I’m sure the appropriate anerobic sealer would work just fine, but proper prep is absolutely necessary. Be sure to clean off all the old sealer and make sure the crankcase faces are flat. Probably best to give the anerobic sealer at least a day to set up before running the engine unless using the appropriate primer….

[Mumbles]

RTV is Room Temperature Vulcanizing sealer but silicone sealers as with most things have improved over the years. Generally, I never use any kind of silicone sealer anywhere on an outboard except for Permatex Adhesive Sealer which I use on gearcases. Crankcases usually call for an anaerobic sealer such as Permatex Flange Sealer (OMC Gel Seal) which is fuel proof when cured. Is it possible these products weren’t on the market yet or copyrighted when your motor was built?

[billw]

I went with the anaerobic sealer. I just couldn’t put RTV on a crank case flange. It’s just not in my DNA. Thanks for the input!

Long live American manufacturing!

[fleetwin]

billw wrote:

I went with the anaerobic sealer. I just couldn’t put RTV on a crank case flange. It’s just not in my DNA. Thanks for the input!

I’m with you Bill….I hate that RTV stuff, and would never use it on crankcase flanges…

[fleetwin]

billw wrote:

I went with the anaerobic sealer. I just couldn’t put RTV on a crank case flange. It’s just not in my DNA. Thanks for the input!

I’m with you Bill….I hate that RTV stuff, and would never use it on crankcase flanges…

[DAN UMBARGER]

I’m a Suzuki dealer and they call for Threebond 1207B sealant for their crankcase flanges. Have used it on all the Suzuki’s I’ve rebuilt over the last 40+ years. I think it’s a silicone based sealant and is gas/oil resistant. I do use OMC Gel Seal on all OMC’s though.

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