Through hull bolts under water line.

[dave.zap]

Hi this ones fairly urgent (cause im out of the water just this week) so sorry if I've missed an obvious past thread on this topic.

I had removed my Zinc from my GRP boat and was attempting to undo some corroded nuts on the inside of the hull and of course the hole bolt twisted around. So what ever seal was set, is now broken.

Assuming I can remove the old bolts without doing any further damage what would be the general procedure for fitting new ones?

Epoxy the bolt in? some kind of resin? What types of bolts should I use and how to generaly restore boats previously water tight status (that I have now broken )

Thanks

 

[prv]

When I fitted new anode studs I just gave them a good dollop of Sikaflex. A little bit into the hole, but mostly under the square plate that's welded onto the stud and goes on the outside of the hull. Don't squeeze it all out as you do the nuts up - ideally leave it to set hard before doing up the final bit.

Pete

 

[maxi]

You will need to buy 'anode fixing bolts', which have flat plates already welded on and are galvanised - they should come with washers, nuts and connector rings for the electric cable. They are not expensive & should be attached with an underwater sealant such as Sikaflex.

It's a good idea to replace these every couple of years or so - before they give up of their own accord.

Don't forget that there must be a full electrical continuity between the zinc anode and whatever you are seeking to protect; propeller, engine etc.

 

[ithet]

I had to cut the old bolts out and replaced using Sika as per PRV's advice.

 

[prv]

They are not expensive

Actually they are quite expensive for what they are - a bit of galvanised studding with a square washer welded on, should be able to be knocked up for pennies but they charge something like a tenner for them. Some of my first ever posts on here were asking about cheaper alternatives. Sadly the going price proved just low enough not to be worth the effort and hassle of making my own, which I guess is the idea.

Pete