Sealing Thru-Hulls Plugs In Aluminum Boat

[JoLin]

I've removed the livewells and plumbing from my Sylvan aluminum and have 5 holes through the transom (below the waterline) that I need to plug and seal. After an attempt with thru-hull fittings and hoses that didn't work perfectly, I've decided to do the following...

I'm going to cut an aluminum spacer to fit inside each hole, and sandwich it between 2 (larger diameter) aluminum washers. My hole saw kit will create the spacers and washers, which will then be through-bolted together. Should make for a strong cover that can't slip out of place. A neoprene washer will seal the bolt head.

Obviously I want a good, pretty permanent seal between the washers and the transom. 5200 is my first thought, but the tube says nothing about bonding to and sealing aluminum. Is there something better?

(FYI, I don't weld and don't know a welder or I'd seal it that way).

Thanks.

 

[jasoutside]

Re: Sealing Thru-Hulls Plugs In Aluminum Boat

Here's how I plugged up my aluminum baitwell if it helps you out any...

http://forums.iboats.com/boat-resto...mph-ss-165-rebuild-545380-66.html#post3942513

I know you are talking about your transom but the procedure would be just about the same eh.

 

[JoLin]

Re: Sealing Thru-Hulls Plugs In Aluminum Boat

I decided to cover each hole using a single bolt through the center, rather than 4 or more around the circumference. IMO, it's just a different method of accomplishing the same thing.

The key to your thread (for me) is that you used 5200 as the sealant.

Anybody else?

 

[JoLin]

Re: Sealing Thru-Hulls Plugs In Aluminum Boat

^^bump^^

I guess 5200's the way to go, then? Thanks, Jasoutside.

 

[Scott Danforth]

Re: Sealing Thru-Hulls Plugs In Aluminum Boat

5200 is an adhesive sealant for below the water line. it sticks to everything from painted parts to fiberglass to stainless and aluminum. it also sticks to skin.

 

[jbcurt00]

Re: Sealing Thru-Hulls Plugs In Aluminum Boat

Yep ^^^

5200 is promoted as PERMANENT, but below the waterline, it'd be my choice too.

Above the waterline 3M 4200 is less permanent.

 

[JoLin]

Re: Sealing Thru-Hulls Plugs In Aluminum Boat

I always use 5200 below the waterline. I know how well it works, but never used it on aluminum. I just found it curious that the tube makes no mention of aluminum, which is why I wanted to double check.

Thanks, guys!

 

[Landof9000lakes]

Re: Sealing Thru-Hulls Plugs In Aluminum Boat

I would install a thru-hull type fitting in the holes and then loop the hoses back to the other.

It would just look like you had those components in place but you wouldn't. And you wouldn't take on water or have patches/plugs on the outside of the boat

 

[JoLin]

Re: Sealing Thru-Hulls Plugs In Aluminum Boat

I would install a thru-hull type fitting in the holes and then loop the hoses back to the other.

It would just look like you had those components in place but you wouldn't. And you wouldn't take on water or have patches/plugs on the outside of the boat

That's exactly what I tried in the previous attempt. Had some problems in 1. finding thru-hulls that would fit precisely in the holes vacated by the aerator pumps, and 2. sealing the replacement thru-hull fittings. The thinness of the transom forced me to make spacers for a couple of them, as the fitting's 'nut' wouldn't screw down far enough on the fitting to tighten it against the transom. That left several that were prone to leak and had to be redone. I never did get rid of all the seepage.

Seemed like a good idea, but in the end I had no confidence in the result. Metal cover plates will work better.