Aluminum boat: Patching screw holes below waterline

[Buzzwindrip]

I have an aluminum boat that had a transducer mounted below the waterline on the transom. Is there a preferred method for plugging the holes left after removing the transducer? I bought some stainless screws and washers, and thought about sandwiching some rubber washers on either side of the transom, then compressing them with the stainless washers, screws, and nuts. Just looking for some feedback from anyone that has done this before.

[Bubba1235]

I would take it to the local welding shop and have them tig weld it.

[dwco5051]

I have done that and it has worked. I used nylon insert lock nuts to make sure they don't work loose. Last one I did on one of my small fishing boats was eight or ten years ago and it hasn't leaked since.

The end result is just the same as used on a through the hull fitting that uses a washer and nut to seal from leakage.

[Expidia]

If they are only the small holes left where the screws were just dab the threads on the new screws you bought with some 3M 5200 or similar product and just screw them back in!

5200:
A faster curing version of 3M™ Marine 4200 Adhesive Sealant. The high performance polyurethane becomes tack free in one hour and fully cures in approximately 24 hours. The seal is extremely strong, retains its strength above or below the water line. Stays flexible and allows for structural movement. Has excellent resistance to weathering and salt water.

[koko1]

If they are only the small holes left where the screws were just dab the threads on the new screws you bought with some 3M 5200 or similar product and just screw them back in!

5200:
A faster curing version of 3M™ Marine 4200 Adhesive Sealant. The high performance polyurethane becomes tack free in one hour and fully cures in approximately 24 hours. The seal is extremely strong, retains its strength above or below the water line. Stays flexible and allows for structural movement. Has excellent resistance to weathering and salt water.

I just had to move my transducer also and that is what I done but on a fiberglass hull.. I didn't put screws back n though, just let some the adhesive cure in the hole, then I had to put the bottom mount smart tabs bracket over it... Worked perfectly...

[arks]

I just had to move my transducer also and that is what I done but on a fiberglass hull.. I didn't put screws back n though, just let some the adhesive cure in the hole, then I had to put the bottom mount smart tabs bracket over it... Worked perfectly...

Same here but with an aluminum boat.
A dab of 5200 inside and out. 3 years so far without a leak.

[rosser1]

RTV works great !!

[109jb]

RTV works great !!

No it doesn't. Many years ago when I bought my Starcraft it had holes like that "sealed" with RTV. Problem is they weren't sealed. The RTV was loose and flapping and letting water in the boat. I re-sealed with 5200 and didn't have any leaks in the 9 more years I owned that boat. Use the 3M 5200 if you want it to last.

[Buzzwindrip]

Thanks for all the replies! I'll hold off on the welding for now, and will get some 5200 sealer. Amazing how that transducer, and two tight fitting mounting screws, with nary a drop of sealant to be seen, didn't leak a drop of water. Oh well, my intent was to get the boat ready to launch on a whim, now that we seem to be getting some decent weather. I ended up spending the day working on the trailer instead.

[5150abf]

Ya, just a dab of 5200 and reinstall the screws, mine hase been like that for a long time and doesn't leak at all and I am an aluminum welder.

Welding will jack up your paint and need to be sanded down then repainted, way easier just to reinstall the screws, alot cleaner fix I think.

[CaptainSkip]

I agree with the 5200. Don't use rubber washers with aluminum, that will cause galvanic corrosion