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Let me kick the dead horse one more time ...

If I want to permanently bond something on my boat, 3M 5200. Permanent. As in grinding it off someday. (which is why several members won't ever use it)

(and does it make a big difference whether I use regular or quick cure?)

If I want a really really good adhesive, but much more removable, 3M 4200.

If I want to seal the gap between my side console (fiberglass) and the boat, White Boatlife Caulk? If I want to prevent water intrusion into a hole with a screw ... is this Boatlife, also?

And finally, never Silicone, because upon later application, neither Silicone nor anything else will stick where Silicone once was.

How am I doing? Comments??

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Hi Bill,
I think you've got it right for the most part. I think of 5200 as an adhesive, not a sealant (although it does seal too of course). My most unpleasant encounter with 5200 was a boatyard using it to seal the bolt holes of my motor mount to the transom. It squeezed out between the mounting plate and the transom, and ripped off a bunch of gel coat when I removed the motor. I swore I would never use it again. That being said, I just used it a couple of days ago to bond a t-nut to a stripped out wood face.

I've never used 4200. It seems to be an intermediate step along the adhesive/sealant curve.

I've used 3 varieties of BoatLife: Life Seal, Life-Calk, and Silicon Rubber. Life Seal is an excellent sealant which cures overnight and has modest adhesive properties. I use this to seal hull penetrations almost exclusively. My technique is to countersink a bit about the hole, clean, and fill with Life Seal, letting it cure overnight. This forms a plug which will not get dragged in or out of the hole The next day I flatten the dollop with a razor/knife and reapply a small amount of fresh sealant on top. I then drive my fastener into the hole. This has both the hole and the threads well sealed. I spoke with the founder of the company, who offered that the most common error in sealing fasteners is applying too much force and squeezing most of the sealant away from the site. The countersinking keeps that from happening.
I used Life Seal to seal the fuel tank cover back to the deck.

I used Life-Calk to join the gunwale boards on my 1985 Outrage 18. It is very stretchy and will accommodate significant wood movement. The downside is it takes a long time to cure.

My use of the Silicon rubber product was in rebuilding a modified grommet for cables into my outboard. It bonded well to the existing grommet material, and filled gaps where I had ground out excess stock.

Dennis

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What Dennis said !!

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Can anyone recommend what is good to use between a cmc tilt unit and the transom by the bolt holes to keep water out?? Is 5200 to strong?

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I use and recommend Life Seal in that application. The 1/2" bolts are holding your motor to the transom. You want a sealant to keep the water out. Life Seal has moderate adhesive properties and will do the job brilliantly.
Dennis

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Get on the LifeSeal early and a damp/wet cloth clean up. Surprisingly....water based sealants are more mildew resistant that those needing acetone, mineral spirits, etc...from what I heard from a manufacturer.
Garris

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Lifeseal's description is "blend of marine silicone and polyurethane". Is it exempt from the silicone ban many here at Whaler Central practice?

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FYI - Sometimes, a heat gun can be your best friend.
Heat will loosen the bond of 5200 in short order.

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I have used 50 lb spectra fishing line to "saw" through 5200 in the past, once the fasteners were removed. It worked, I cleaned up the residual with sand paper.