Screws + fixings on aluminium boat

[seasponge]

I’m relatively new to boating and bought an old second hand aluminium boat a couple of years ago. I am slowly learning all the boats do’s and don’ts, both on and off the water.

What is the practice for using screws/fixings into aluminium hull. I’m assuming 316 stainless steel, but then what about the use of dissimilar metals? I’m looking at two scenarios; outside boat below water (ie to mount a transducer bracket), and inside boat above water (ie to mount rod holders to inside back of boat and cup holders and fish finder display to dashboard).

[PaddyT]

Duralac on everything- dont forget even having two different grades of aluminium will potentially cause dissimilar metal corrosion. Nylon sleeves on fittings can be a help too- but its bloody hard to completely overcome.

[raging]

Probably the same thing but I use tef-gel

[Berleyguts]

For the transducer bracket, why not consider getting someone to weld on a mount for you? Saves drilling holes through your transom so close to the waterline.

[Welster]

It’s hard to know what’s the best way.

We use Tefgel as above as one option.  Fittings like rod holders we drill the appropriate size rivet holes and prime and paint them.   We use sikkafkex under the rod holders to seal them, rivet them down and clean off any excess.

Other fittings we have drilled over size holes primed and painted. We used nylon fixings with sikka or tefgel on and around the hole.

We avoid self tapping screws as much as possible.   They break the paint moisture gets under it, the aluminium oxidises and the bubbles grow from there.  That’s my take on it anyway. 

To us it’s all about stopping moisture and salt getting near raw aluminium at the fixing point. 

It’s a bit of mucking around.   Another thing we have done is wax the top deck off the boat trying to prevent any minute imperfections in the paint allowing moisture through.  That makes it slippery though.

I hope that helps.  Good luck. 

 

Edited January 29, 2018 by Welster
Typo

[rickmarlin62]

I amostly used rivets..end rivets so no water intrudes..if not 316 s/s bolts  oversize holes  sikaflex or heat shrink...rick

[Guest Guest123456789]

For the transducer mount I used an Old ice cream container to make plastic washers. Perfect material, helps with watertight seal and eliminates electrical interference or risk of a reaction to the metal. Plus it cost $0 

[Berleyguts]

38 minutes ago, flatheadluke said:

For the transducer mount I used an Old ice cream container to make plastic washers. Perfect material, helps with watertight seal and eliminates electrical interference or risk of a reaction to the metal. Plus it cost $0 

And it’s an excuse to eat more ice cream. ??

[Guest Guest123456789]

26 minutes ago, Berleyguts said:

And it’s an excuse to eat more ice cream. ??

Does make it harder to get up on the plane though ? 

[seasponge]

Thanks for all the replies. It appears i'd underestimated the issue. I havent put any fixings in yet, but was about to. None of the videos i watched about transducer installation mentioned anything about treating the screws or holes. 

Although, it appears the previous owner or (owners) weren't too concerned. There's fixings everywhere and i havent seen any sign of any duralac or  tef-gel (man, that stuff is expensive by the way).

The boat is old, and there's signs of corrosion at the transom. 

 

Rick, for rivets, do you coat them in anything prior to installation?

[Berleyguts]

29 minutes ago, seasponge said:

Although, it appears the previous owner or (owners) weren't too concerned. There's fixings everywhere and i havent seen any sign of any duralac or  tef-gel (man, that stuff is expensive by the way).

You don’t need a lot of Duralac. It goes a long way. ? I just dip the screws into the nozzle of the tube and the screw or bolt is coated. I just changed rod holders over from riveted plastic ones to s/s with a gasket and s/s bolts and lock nuts and my tube of Duralac had been sitting in the garage at my old place for a few years and I’ve been in Port for 10 months. I keep a bit of gaffer tape around the cap to keep air out.

[rickmarlin62]

just a smear of sikaflex  it works on everything haha

[seasponge]

On ‎30‎/‎01‎/‎2018 at 8:31 AM, Berleyguts said:

You don’t need a lot of Duralac. It goes a long way. 

 

18 hours ago, rickmarlin62 said:

just a smear of sikaflex  it works on everything haha

I think i'll try to go sealed rivets wherever practical, with plenty of Duralac or similar. 

Are aluminum sealed/closed rivets readily available. I tried the major hardware store, but they didn't have sealed rivets.

 

[rickmarlin62]

if bunnings don't have them try a metaland agent

[Berleyguts]

Or your local chandlery.

[Welster]

They might call them cherry blind rivets.