Filling screw holes from old transducer

[Tips Up]

What is best to use here?

I've removed an old transducer and installing new one.
I usually put a bit of sikaflex in the new screw holes before I screw anything into hull.
Just use the same to patch old ones?

 

[Fishalot]

I use Marine Tex, an epoxy. What you might want to consider as an alternative is getting a small piece of starboard and reusing the existing holes to mount it to the transom. That's what I did on mine so any future changes to transducer is just holes in the starboard rather than transom.

 

[sly_karma]

^ I rebuilt my transom a couple years ago and was squeamish about drilling holes in it after so much work to get it pristine again. I made a block of clear plexiglass about 6x6 and glued it to the hull using clear 5200. Then the transducer can fasten anywhere you like on that block. If I go with trim tabs I'll have to screw into the transom though, I they will put too much load on glued-on blocks.

 

[gungadin]

First thing is to inspect the old screw holes for any water intrusion. If there has been any, drill the holes out to a larger size, large enough that you can insert a q-tip. Mix up a small batch of liquid epoxy and dip the q-tip into it. Push the soaked q-tip into the old screw holes, do this several times over a period of five minutes or until you are satisfied that the epoxy has soaked in and is completly covering the old holes. Put a little of the liquid epoxy on a piece of paper as a test. When the epoxy hardens to sticky consistency, mix up a thick batch of epoxy, that doesn't sag, and fill the holes. You can clean off the epoxy before it sets up with isopropyl After the epoxy hardens (overnight) you can mount your new transducer. If you are using a piece of starboard or wood as a mounting platform, mask off and sand the appropriate area. If you are using wood be sure to seal it on the mounting area and sides (but not on the side that goes to the transom) with liquid epoxy. Mix up another batch of thickened epoxy and apply it to the area that you sanded. You will need to clamp the wood in position, tight enough that it does not move but not so tight that all the epoxy squeezes out. One of those long wood clamps set up to push and braced against a solid object works well. Clean off the excess epoxy and let it harden overnight. I generally try to get the lower edge of the wood along the trailing edge of the hull. You can fair it in after the epoxy hardens. Using the appropriate length fasteners mount your new transducer to the wood/starboard only. You can also paint the wood in a matching hull colour should you wish. I use West System epoxy, but that is a personal choice.

 

[Rayvon]

I used 3/4 starboard ,cut to size and shape and ran it through my table saw at 1/8 deep and about 1 in. apart in both directions to give Sikaflex something to grab onto.As gungadin said mask off the area around where you want to place the starboard and sand the gelcoat w/ 80 grit paper,wipe w/acetone,Sikaflex starboard back and push firmly into place.No need to clamp,it won't move.I've done a few boats this way,no failures yet.I use Sikaflex 291 fast cure.

 

[Fishalot]

Very interesting to read that Sikaflex worked on starboard for adhesion. I have read that nothing will stick to it.

 

[casper5280]

After redoing my transom this year I will never drill a hole in it again. The holes that I have had to were all drilled twice the size needed and filled with epoxy and left till it was cured, then redrilled for the size needed. Going to be doing the Starboard thing for the transducer. found this for working with Starboard

 

[Tightlines22]

Very neat procedure. Hadn't seen that before.

 

[sly_karma]

Thanks for posting, Casper. I never knew about the heat treatment process for bonding to HDPE. Had a bugger of a time putting in some mounting blocks for rod holders. I ended up glassing them on, next time I'll pull out the torch.