www.iFourWinns.com

I just removed two old transducers from the transom of my recently purchased 1987 215 Sundowner. Only one was still connected and that to a 17 year old depth finder which is being retired. I'm going to install a modern unit with navigation and side-scanning capability but meanwhile I have to deal with holes in the transom.

The old transducers were poorly installed...."Bubba" used silicone which I'll have to clean up before I can contemplate anything else.


What I'd like to hear are your recommendations for dealing with the empty holes. I was thinking that after removing the silicone I would grind a small concave depression at the opening of each screw hole then fabricate small metal plates from aluminum or stainless and drill them to match the screw patterns - then I would take a quality marine caulking, squirt some in the holes and on the underside of the plate and screw the plate down, squeezing the caulk into a gasket. The tiny concave depression would form an O-ring of sorts around the screws. I could also accomplish pretty much the same thing using fender washers at each hole but you get the idea. One wild card is having to drill additional holes for the new transducer but until I settle on a unit I have no clue what impact it will have.

Do you have any other ideas? I'm very open to suggestions.

Tim

_________________
1987 Sundowner 215
Mercruiser 230/V8 - Alpha One Gen 1
Previous Boat
1973 Starcraft 21' Chieftain 120 HP Mercruiser I/O
PADI Master Diver
IANTD Technical EANx Diver
Commercial Pilot
Flight Instructor

I think what you plan is really good. Personally, I would just clean it up completely and use some 3m 5200 caulk (24 hour cure) and fill the holes as much as possible, then wipe smooth to the finish, so that the only caulk is in the hole. 5200 will barely be noticeable, and will work forever

_________________
Current:
2000 Sea Ray 380 Sundancer "still Livin the Dream"

Past
2002 268 Vista 5.7 GXI "Livin' the Dream"
1996 Rinker 192 Captiva. "The Simple Life"
1999 Yamaha XLL 1200 Waverunner.
1976 Mercury Marquis tri hull 120 hp

On my current boat and my previous boat I installed a transducer mounting plate which is a 1/2 or 5/8 thick Starboard panel. I cut and shaped it to fit, sealed it completely to the transom with 3M 5200, and installed the 2 mounting screws while the 5200 was still wet. I taped the surrounding area and smoothed the 5200 into a fillet to seal the edges. With this panel in place I can change transducers without compromising the transom. The transducer mounting plate came from Cabelas.

_________________
Surface Interval: A scuba diving term for that time between dives to relax and prepare for life's next great adventure.

Current boat: '02 FW 268 Vista
Previous boat: '95 FW 190 Horizon

Make your pattern in the new material your going to use. Drill the currant holes bigger in case there is any wood issues and fill with Marine tex with a syringe to make sure you get it all the way in. re-drill for the new mount and use 3M 4200 for the screws.
Trying to force thickened epoxy into a blind hole with a putty knife always leaves an air bubble at the bottom of the hole. Filling from the bottom forces all air out of the hole.
You can use 404 High-Density Filler or 406 Colloidal Silica Filler to thicken the epoxy

I would be happy that Bubba had used a sealer, even if it was just silicone.

At the very right-hand side of your picture, you can see a previous hole that was filled with 5200 or similar. I don't think you need the plates...just do as the three posts above me had said. Remove the silicone, drill the hole open by 1 drill size larger, then fill with 3M-5200, MarineTex or Thickened epoxy.

I've never had trouble pumping 5200 into a hole using just the tapered tip. IMHO I don't think it matters if there is a little air bubble at the bottom of the hole, as long as you get it filled at least 1/2" deep.

Then 3M-4200 is better for installing the new transducer, as it has some flexibility. (5200 is very hard/non-flexible)

_________________

"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings

Funny, I hadn't noticed the other hole. I will say that the screws seemed to be in very solid which makes me hope that the wood is in good shape. The replies to my post are all good advice which is what I've come to expect from this group, thanks!

Perhaps I shouldn't have used the pejorative "Bubba." I'm also a member of the classic military Jeep community and that term is used to describe modifications made poorly which damage or degrade the value of such vehicles..... my complaint about silicone is that it seals poorly and interferes with any subsequently applied sealers. Silicone has it's uses, but not below the waterline

The use of some kind of mounting pad for the new transducer seems like a good idea. No additional holes in the boat and the ability to loosen the mounting screws to adjust the position of the unit without breaking the seal.

Tim

_________________
1987 Sundowner 215
Mercruiser 230/V8 - Alpha One Gen 1
Previous Boat
1973 Starcraft 21' Chieftain 120 HP Mercruiser I/O
PADI Master Diver
IANTD Technical EANx Diver
Commercial Pilot
Flight Instructor

Informative post. I noticed old holes in mine that didn't look great so i cleaned it all out and filled them with spectrum gelcoat paste but i think i'm going to dig it out and re-do it. it still seems to be holding good but i had a couple 'scrapes' on the keel that i fixed with the same stuff and noticed it all broke loose. after seeing that not sure i trust the stuff in the transom either. thinking i either use the starboard mounting plate mentioned and fill those old holes with thickened epoxy. i replaced my bunks on my trailer and extended them slightly then put the boat up too far and broke my depth finder transducer so need to replace that. plan to move it over a little to clear the bunk so need to fill the old holes anyway.

Good tricks here to use the old holes for the new mods.

West Systems 610 is pretty good for filling holes.

https://www.westsystem.com/specialty-ep ... -adhesive/

_________________
2004 Vista 298
Twin 5.7L Volvo Penta GXi-E

That looks pretty good.

I accidentally put a hole thru the side of my boat while mounting a power distribution block. I used the 3m caulk on the inside, but on the outside used marine epoxy, which comes in white, is sandable, and looked the best compared to caulk.

_________________
2008 Four Winns h180 Bowrider
3.0 Volvo Penta

2013 Dodge Durango HEMI