Polyurethane, polysulfide & ABS transom...

[lineofsight]

The Mercury Airdeck has an ABS sheathed transom that needs a couple through bolts sealed below the waterline.

Reading about the various sealants polysulfide (3M 5200, 3M 4200 & Life-Calk) are incompatible with ABS (the Polyusulfide attacks the ABS, hardens & cracks). Polyurethane (Life-Seal) is supposedly more aggressive than polysulfide.

Does that leave me with a polyether (3M 4000)? Suggestions?

Also want to put a brass tube through the transom above the waterline for when I want to use the engine bolts (through the tube). 3m 4000 good enough to hold them in place (thinking through bolt, stainless washer, rubber washer, transom) or is an epoxy needed (Marinetex)? Suggestions (photos?).

[lineofsight]

Should this be helpful to others with same question - response received from Boatlife:

It can be confusing. Life Calk (polysulfide) is not compatible with ABS plastics, nor is a pure polyurethane. Life Seal is a hybrid of silicone and polyurethane, and what makes it so special is that we were able to remove the performance detractors of both the silicone and polyurethane and leave only the great attributes of each. Yes, Life Seal is compatible with ABS and the polycarbonate plastics, yet it has great adhesion, something you normally don’t get with silicone.

In answer to your next question, no, we do not offer a polyether.

[Erin]

My engine supplier advised me that plain old silicone is absolutely fine for engine bolts. Certainly worked for me.