Re-Bedding Deck Fittings

[Mowjo]

Ok guys and gals heres one for you and I'm sure i'll get ten different answers,, I have to re-bed all my deck fittings due to several leaks, at the moment the ones causing the main problem have been bedded with silicone mastic, the others are bedded with mastic tape which I did last year and Freeman swears by, but they still have a few leaks, so is there a better more reliable way of re-bedding them, I know about not fully tightening the fittings until the mastic has set up a bit, then re-tightening them, but is there a more realiable product for the job,,

Regards Frank,,,,

[Happy Jax 3]

Hi Frank

To be honest I have used many types of mastic/silicon sealers over the years, Sikaflex, Silastic etc.. with and without success. More recently I tend to use Marine Dow Corning, if it can bond large fish tanks together without leaking, that does it for me. I must say I have never had a leak since.

[Antares_9]

Like many jobs it’s not just about the materials you use, though (the right type of) Sikaflex is one of the best for this purpose. Preperation, Preperation, Preperation, make sure everything is clean and dry , countersink the deck holes a little to allow sealant to have a larger area so it can flex (thin layers squeezed out as you tighten do little good) at the same time if possible slightly countersink the underside of the fitting for the same reason. Do not fully tighten the fitting until the sealant has cured, it then becomes a gasket and you can do the final "nipping up". Also remember to use a bit of sealant on the penny washers or backing plates you use on the underside of the fitting again with a little countersink on the boat if accessible. An area often neglected is the underside of the bolt heads on the outside.

[Mowjo]

Thanks Folks! Antares! I do all that but I still get leaks, I can only think that it's something to do with the GRP on Freemans being quite thin especialy topside and it allows more flex than normal causing the seal to break, I never had any problems with my old Seamaster, but that was at least half inch thick,

Happy! that sounds like a good idea I'll give it a try, I should have thought of that seeing as I used to make my own fishtanks,