Mounting stuff to the hull

[Jack Long]

As of yet I haven't drilled through the outer skin of my boat. I feel a little bit like the adage about parachuting- why jump out of a perfectly good airplane? Why poke a hole in a boat that floats?

However, I scored some phat lewt yesterday. Two of them require mounting. One is a set of dinghy davits which I haven't decided how to handle yet. The other is an outboard bracket which strikes me as a good idea since... I have an outboard. Oh! I actually have a swim ladder I need to install too.

Okay, so in both the case of the swim ladder and the outboard bracket I will need to put holes in the hull. For the swim ladder I figured I would just drill pilot holes and thread a screw (you mount the bracket and the ladder sits inside it). Should I coat the screw with something to add water tightness? Gasket sealer or something?

For the outboard bracket I imagine I would want backing plate? Now, with the swim ladder there are two brackets- both very small so I am not worried about matching the curve of the boat- but with the outboard bracket I feel like something should be done. The bracket is probably 6 by 8 inches or so? My transom has a curve to it. Do I need to do something to match the outer curve to the bracket and the inner curve to the backing plate? And again, do I need to use some chemical sealant?

Thanks,
J

[speciald@ocens.]

Thru-bolt everything if you can with back-up plates or fender washers.

[Jack Long]

Consider it done!

What about a sealant?

[SkiprJohn]

aloha Jack,
Whenever you penetrate the hull, you should use a sealant of some kind. If you want the attachment to be there permanently (forever and can never remove it) use 3M 5200. If you want to be able to remove it to replace it then use a polysulfide sealant (Boat Life) makes one. If you just want to make a gasket then you can use silicone sealant. All are messy to use so mask any area that you don't want the sealant to dribble. I would try very hard to make a backing block to match the curve of your inner hull and the same with the outside when you are ready to attach your motor mount. Teak lasts forever, Oak is good if it is painted, Doug Fir if you don't mind replacing it in a couple of years.
You have the option of touring several boat yards there in the SF Bay area. I like the one out in Alameda that has lots of boats to look at and compare. I can't remember the name of it. Maybe Olson?
Screws are only a good idea if you cannot reach the inner hull to use through bolts. If you do a pilot hole and then force a screw in your fiberglass it will break the glass and weaken it surround the screw.
Good luck in your projects.
Kind regards,
JohnL

[SeaKing]

when you drill the holes, you should coat the inside of the holes with epoxy to permanently seal the fiberglass and core material if there is a core.

Also some Boat life caulk in the hole around the screw/bolt

[imagine2frolic]

Svendsen's yard

[Cheechako]

use 5200 and no worrys. Small areas like that can be taken off. You may have to make a faired block to match the hull to the Outboard bracket... you want the push of the motor to be on the hull not on the screws. You might be able to fill with 5200 up to 1/4" max to accomplish this...tichetn lightly... then let it harden for a week and retighten.

[SkiprJohn]

Aloha Jack,
Svendsen's yard is one of the good ones to go look around and ask questions. Great folks there and they don't mind questions.
kind regards,
JohnL

[easterly]

Why does everyone badmouth 5200 as "forever sealant?" It comes off just fine if you use the proper tools. It does what it is designed to do.

[David M]

In Alameda there is Nelson's Marine, Svendsen's Boat Works and Mariner Boat Yard. I know, I live in Alameda.