Thru Hull Pick ups. (Removing and plugging the holes back up). Can it be done?

[BAron Sportsman]

I have two thru hull pickups (scoop type but with no locking screw holes), that were fitted 5 years ago to feed a 4 pot Volvo. About 18 months ago I swapped out completely for a 4.3 V6 Merc and made the thru hull pickups redundant by simply joining the two together with hose and closing both ball cocks.

Stuck my head under the boat this morning to inspect the trailer rollers and noticed the left pickup has spun about 15 degree?s to the left but the nut on the top inside the engine bay has stayed put. The nut has tried to move but hasn?t. The entire floor and engine bay was re-flow coated when the engine was changed over and the flow coat around this one does show a micro-hair line crack in the flow coat but it hasn?t actually moved the nut with the pickup.

That tells me all the sikaflex around the pickup and in its shaft threads must also have crack fractures when it?s turned. It also tells me the pick up must have actually tightened itself up rather than loosened off. I've not seen any signs of water at all in the boat since the engine change but leaving it like this is potentially a disaster waiting to happen in my opinion. I?m thinking it?s done it because the boat is capable of much higher speeds now with the V6 and the increased friction on the scoops has turned it. I never in my wildest dreams expected to see this. They were cemented in tight with sikaflex everywhere around them and never showed any signs of moving until now.

I?m keen to get rid of them completely but I cant see how you could repair two holes through a hull like that successfully without extensive money and major fibreglass reconstruction.

My thought?s are to simply replace the scoop type now with the round flat ones to eliminate the friction on them and just leave them blocked of once more at the top with the ball cocks. Better yet, is there actually one of these flat type that is actually solid instead of hollow that is deliberately used for this type of plug to seal off holes where pickups once lived? It would be a much better plan if the product did exist.

 

[Scott Danforth]

remove the thru-hulls, install large stainless steel carriage bolts with lots of 3M 5200

 

[fhhuber]

Fiberglassing the holes shut is "educational" in fiberglass repair techniques.

Bevel out the hole to appx original dia + 20X thickness of the fiberglass

Attach a backer of some sort on the inside of the hull to help you work. (coroplast held in place with a brick might do. This will peel off when the fiberglass cures)

Layer in the cloth with resin building up to the needed thickness.
Some apply first layer full area coverage and then make each new layer smaller.
Some lay in the small layer (size of the original hole) first and then each layer larger to fill the patch area. Either works but the second is slightly neater. If you are using poly resin and some mat layering then you use the second method every time and last 2 layers are cloth for smoother surface.

Let the patch cure (its watertight and can float when it cures)

Sand and prep for gel coat patch.
Apply the new gel coat building up a little too thick.
Sand and buff down to where (if color matches) you can't find the patch.

Yes, its quite a bit of work. Its the REAL right way.

anything else is a plug in a hole.

 

[Lowlysubaruguy]

Have a machine shop make you a beveled aluminum plug. Something thats smooth highly polished and wont catch on things in the water or trailer. OK Id throw a piece of aluminum in my lathe and make something that fit it perfectly with just enough room for some marine silicone between it and the boat. If you decide to use them for something like a live well pump or raw water wash down later your half way there. On that note do you have a raw water wash down station if not find one that the pump intake fits this hole and install it there. Now youve killed two birds with one stone.