Transom Replacement

Hey guys, I know there are 10000 different post on proper ways to rebuild transoms/fix old problems etc. but I am a complete amateur when it comes to this kind of thing and need to make sure I am on the right track/see which direction to head now. I have a 1983(ish) Ebbtide Dynatrak bass boat which had the tilt and trim replaced on it about 2 years ago. Well the very next trip to the lake after it was fixed I realized the boat was taking on a great deal of water. We rushed back home and realized that the lower motor mount had cracked through the fiberglass and created a entry point for water.

Well Monday we decided to pull the motor and get an idea of how bad the transom really was, it appeared like the interior wood was still good until we opened up the cracks a little farther and realized all of the interior wood was rotten. So we cut the cap off the transom and stripped the whole interior of the transom out. The two "cracks" in the rear skin of the transom were made bigger into on hole approx. 3 inches tall and about 10 inches long. The interior skin had already been cut into a hole at approx 2 inches tall and about 6 inches long.


We are planning on using 5 gallons of seacoast poured in the transom (it has been ordered and is on its way) but I am just a little concerned with how the fiberglass will holdup or if we are even taking the correct methods to do this rebuild. We have began putting fiberglass over the interior skin hole, I just want to make sure we are going the right way. Any tips/tricks would be greatly appreciated! Below is a picture of the back of the transom with the size hole we have at this moment.

 

Sea Cast will not make the 'glass repairs you need on the skin. It's just a core material. To fix it, you need to grind back the damaged areas into good mat, then replace the missing material with more laminate. Then you can pour in the Sea Cast.

 

That is what the plan is, I just wanted to make sure that those holes were not too much of a problem for fiberglass, I have never used it. So the best thing to do is add some layers of fiberglass then sand if smooth then add seacast in and ill be on the right track?

 

The trick (or problem, depending on how you look at it) with Sea Cast is getting a truly clean bonding surface, inside the transom void, before the pour. Pay extra special attention to this portion of the project, as it's the only way this stuff will work (it has to have a really good bond).

As to your holes. The boat was 'glass before, it'll be fine if it's 'glass again. Make sure you use just as much, if not a little more material when you patch the holes. Bondo and similar isn't the stuff. Boat resin or epoxy and 'glass is what you need. You'd also be wise to epoxy "bond" the fastener holes to prevent future issues.

 

We have basically scraped the inside of the transom skins near free of any wood. There are still a few small splinters that are near impossible to get out, will this be sufficient for Seacast? What if we took 2 sheets of very very thin aluminum and mounted one to the front skin and one to the rear skin for the seacast to bond too (add in their aluminum bonding agent.) Would this be a better fix and also add strength to the fiberglass skins?

 

Nope, just scraping will not work, it has to be sanded with a coarse grit, which adds "tooth" to the surface for the resin (Sea Cast) to grip. 40 grit or less is ideal and typical for polyester resin.

Aluminum skins just add more bonding issues to the mix and I wouldn't bother. The only (easy) way to improve the strength of the skins, are to make them thicker with more laminate (fabric and resin). For Sea Cast to work, both skins have to be "sound", as again, it's just a really heavy (and costly) core material. The skins bear the loads, the core just keeps the skins separated and attached to each other. So, if the bond surface isn't ground clean with coarse paper, the skins will not stay in contact with the core and you'll be relying on just the outer skin's stiffness, which will fail quickly. Technically, you could use aluminum, but thin sheets will not add much stiffness. You'd need 12 gauge or 1/8" plate, to make any appreciable difference.

 

try the following-

use carpet tape, a lot of it, to stick a scrap piece of half inch ply to the outside of the transom for support. Cut some wood strips to stuff down the slot to position the front skin equidistant from the aft skin. This is important, be fussy and get any junk out of the way of the strips. Stabilize the front skin somehow so you can remove the spacer strips from inside. Take a 36 grit 4 x 24 belt sander belt and fit it over a wood block the correct thickness and screw a handle on the side of this and go to town. You want almost no pressure and a lot of patience. Tell everyone you know that they owe you fifteen minutes on the stick if they ever want to set foot on your boat again. you're done when you have about a breadbag full of FG dust. It should be flat as a countertop in there and rock hard. Its important to keep the skins flat and properly spaced during the entire drama. Does seacast come with instructions?

 

philsweet thank you i will def have to try this out, yeah it came with instructions. Ordered it 2 days ago and got here today. (if nothing else they are fast at shipping!) PAR thats what i figured but had read a few places that it could have "splinters" didn't believe it but figured id ask anyways! I will update pics as soon as possible, we have put a few pieces of fiberglass on to fix the holes. Def a long process but it keeps that $2000 the shop wanted for this in my pocket, for the most part