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Old 04-14-2014, 07:38 AM   #1
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Default Confused - epoxy or sealant/tape?

17-foot fibreglass hull back from a major refurb, including new transom etc. Need to re-attach all deck fittings and engine.

For deck fittings: Was planning to over-drill, fill with epoxy, and re-drill. But then came across this very helpful article that relies almost exclusively on butyl tape (

The tape approach will save a lot of time, but some of the fixtures are screwed in rather than bolted on - so I'm wondering if I should bite the bullet and just go the epoxy route regardless. What do you all think?

For engine mounting: The epoxy route (I think) would be needed since there's a lot more wood core to protect/seal. But I'm wondering if these epoxy 'hole liners' will be strong enough to handle the mounting bolts? Can we even consider the tape approach here? Obviously I haven't done this before : )

Please share your advice/insight!
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Old 04-18-2014, 09:04 AM   #2
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Typically the over drill and fill with epoxy is a step in addition to your preferred sealant, not in place of the sealant. This approach provides you protection, because invariably most any sealing method has the probability of failing at some point, and back filling with epoxy will prevent any water intrusion into the core material given a future sealant failure.

I believe in the article that you reference it specifically states that the butyl tape is insufficient for below the waterline repairs. Typically, 3m 5200 or equivalent would be used for below the waterline repairs of this type, but again, this is just a structural sealant. In place of the butyl tape for your deck fittings you could also use 3m4000 or equivalent; in this application these are all just primarily sealants.

In your case, I think the most appropriate course would be to over drill and back fill with epoxy to ensure the integrity of the core, and also use the sealant of your choice when installing the hardware.

Also, I believe that the epoxy should be sufficient in compression to prevent damage when tightening your bolting on the transom, but often some form of a crush sleeve is used when bolting a cored structure. I have usually seen these as a PVC pipe of appropriate dimension being epoxied in place on the transom, although I'm sure that aluminum or stainless steel could be used, but I expect that would be overkill.
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Old 04-18-2014, 09:25 AM   #3
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Thanks for the comprehensive and very helpful reply. I'd completely overlooked the fact that the tape couldn't even be a contender for below the waterline use!

TBH, I'd never considered using both approaches simultaneously (for the deck hardware), but you make a valid point that sealant failure is always a possibility for a number of reasons.

Regarding the engine mounting holes, there is just so much contradictory information out there! Those against any kind of sleeve/insert say that compression is needed, and the discussion goes on and on!

I think I'm going to use a transom plate to spread the load, use thin epoxy on the holes and let it seep into the wood over a couple of days/coats, and then mount with a suitable sealant as professionally as I can : )

I confess, I just don't have the skill/experience to be messing around with resin in that critical area with those kinds of loads, vibrations and all that!

But I will probably do as you suggest for the deck hardware, where any mistakes that I make will not have serious consequences : )

Thanks a lot for the pointers.
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