Polysulfide, Polyurethane, Polyether & ABS Transom... Am "poly"confused

lineofsight

Cadet
Joined
Jul 12, 2012
Messages
12
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?).
 

ajgraz

Lieutenant Commander
Joined
Mar 1, 2010
Messages
1,858
Re: Polysulfide, Polyurethane, Polyether & ABS Transom... Am "poly"confused

Re: Polysulfide, Polyurethane, Polyether & ABS Transom... Am "poly"confused

Of the 3M products, the 4000 material is the one most recommended for plastics, and based on 3M's own testing it appears to be the best of these choices for ABS--though perhaps still not great:

4000:
http://multimedia.3m.com/mws/mediaw...6EVuQEcuZgVs6EVs6E666666--&fn=60440094930.pdf

4200:
http://multimedia.3m.com/mws/mediaw...zHvTSevTSeSSSSSS--&fn=Fast Cure 4200 Rev2.pdf

5200
http://multimedia.3m.com/mws/mediawebserver?SSSSSu7zK1fslxtU48_eoYtvev7qe17zHvTSevTSeSSSSSS--

I have my doubts that epoxy would stick well to ABS either. I think I would use the 4000 for all the applications you describe, it is rated for above and below waterline, and it also holds up well to UV. You won't need the rubber washer either, just put a dollop under the stainless washer and let it extrude into it's own seal.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: Polysulfide, Polyurethane, Polyether & ABS Transom... Am "poly"confused

Re: Polysulfide, Polyurethane, Polyether & ABS Transom... Am "poly"confused

You also have the option of using Silicone RTV as long as you let it cure for 24 hours before water contact.

No matyter what you use, take a countersink and chamfer the hole so there is a "wedge" that the sealant can fill--in effect creating its own O-ring.

Hmmmm! That's a thought--how about an actual O-ring? Someday I may try that.
 

lineofsight

Cadet
Joined
Jul 12, 2012
Messages
12
Re: Polysulfide, Polyurethane, Polyether & ABS Transom... Am "poly"confused

Re: Polysulfide, Polyurethane, Polyether & ABS Transom... Am "poly"confused

Appreciate the replies.

Will go with the 3M 4000 then.

For the motor mount through bolts the washer is needed as the hole itself wont be filled - will "4000" the sleeve (brass tube) through the transom and the bolts will run through that when used to secure motor.

Had thought about a mechanical seal using a washer that has a thicker inner radius just like an o-ring but not this time.

Good point on the chamfer - good to have some mechanical help.

Cheers.

---- EDIT ----

Just got this from Boat Life manufacturer:

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.
 
Top