Below the waterline sealant for screw holes?

First time aluminum boat owner here. The previous owner upgraded the transducer and did a real nice job mounting it on a block glued to the transom. But I don't really like the looks of the sealant around the previous screws from the original transducer. If this were a fiberglass boat I would be using 5200. Is that what I want to use here? Or is there something better for aluminum boats?

rpt50 said:

First time aluminum boat owner here. The previous owner upgraded the transducer and did a real nice job mounting it on a block glued to the transom. But I don't really like the looks of the sealant around the previous screws from the original transducer. If this were a fiberglass boat I would be using 5200. Is that what I want to use here? Or is there something better for aluminum boats?

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5200 below the water line. 4200 above. 5200 is near permanent. 4200 you can get the screws back out.

I always use Life Calk Polysulfide for anything underwater. Been using it for over 30 years on sail and power boats. IMO, 5200 is too permanent.

Tin Man said:

I always use Life Calk Polysulfide for anything underwater. Been using it for over 30 years on sail and power boats. IMO, 5200 is too permanent.

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That was great stuff, just takes to long to cure....my old Lyman was sealed up with that stuff...never had an issue after.

Specs on Life Calk....I began using it as I had teak on my sailboats, then began using it on many other items.....deck hardware, railing, etc. It's very versatile.

Per Boat Life:

"A long lasting, permanently flexible marine polysulfide sealant which can be sanded, painted***, and used above and below the waterline. Tack-free in 1 to 3 days, excellent resistance to teak oils, gasoline, and diesel fuel. Ideal for teak decks, to bed deck and hull hardware, seal thru-hull fittings, and underwater seams. Will bond to fiberglass, wood, metal, glass, and itself. Cures to a firm flexible rubber seal with excellent waterproofing and adhesion qualities. Can be applied underwater for emergency repairs. Can be applied to damp surfaces."

Life caulk or 4200 for me…

If possible, I install solid rivets into any holes under the waterline, no sealant needed