View Full Version : Seacast Transom Replacement w/Pics

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08-18-2007, 01:12 PM
Here are the pictures I promised:

Here is a shot of the transom once the motor was removed.

You can see all the holes in the transom, some had been sealed, some had not.

Here is a close-up of where the engine was literally sinking INTO the rotten transom

Seacast says use a chain saw, so I touched it to the top of the transom. Sunk right in.

Using the chain saw really was as easy as Seacast said it would be. The rotten wood came out just like mulch. Notice the soft brown shreds all around. Because the wood was soft, it was easy to shave right up against the glass. I finished the wood removal with a chisel mounted to a piece of 1x2 maple, and then used a shop vac with a piece of 3/4" hose on it to get everything clean as a whistle inside.

Then I used a grinder and glass tape to close the holes, damaged areas and giant scuppers. Then I poured the Seacast. (sorry, no pics- I had my hands full, and I didn’t want to mess anything up)

Pouring the Seacast was almost a non-event. You mix it up as directed, and pour it in. I used a stick to push it around and then thumped it with a rubber mallet to release any trapped air bubbles. I laid a piece of glass tape across the top, and three hours later, I had a VERY solid transom! I couldn’t be happier!

The patch work I did to the skin of the transom needed to be cleaned up, so I mixed powdered glass into some resin and skimmed it flat. Very easy, if you’ve ever done any drywall work. Sand it and do it again, and she was ready for spraying gel coat:

Here is a picture of the transom after spraying. Sorry about the haze, the camera had been in A/C, and I grabbed it for the pic, and it was 100 degrees outside, hence the condensation.

And that’s pretty much it. Seacast really lived up to it’s claims. I already knew this from others on this board, but I’m glad it proved true for me, too. I'm confident that this transom is stronger that it has ever been before, including when it was brand new.

In summary... It took me 5-6 hours to get the transom cleaned out over several afternoons, less than 1 hour to tape the holes shut, 1 hour to pour the Seacast, about 4 hours over a couple of days to skim out the repairs and about 3 hours to spray the gel coat. I will buff and wax the new gel coat, (about 2 hours) and put the motor back on. (about 1 hour)

So the total investment for replacing my rotten transom is $497 in materials and 17-18 hours of my time in the evenings. It would have been a LOT LESS, had the damage to the fiberglass not occurred, probably more like 10 hours.

Hopefully, I’ll finally be back on the water by next week.


08-18-2007, 08:45 PM
Nice lookin clean job!

08-19-2007, 10:09 AM
Jim-are you talking about how I did my transom? I would be happy to. Just let me know if thats what you mean before I type it all.:))

08-19-2007, 02:34 PM
I am facing the exact same job on my old Grady White. After the stuff hardens, can you mount a bracket to it for an outboard (my hull now is set up for an I/O) or is there further reinforcing that would need done?

08-19-2007, 04:08 PM

I removed the engine, and cut off the transom cap with a grinder.

Then, where the engine had sunk into the transom, I ground the gelcoat back and used 4" wide, 9 ounce fiberglass tape, and taped it shut with poly resin, as well as other spots that needed to be closed up.

Then I poured the seacast, let it set, sanded and skimmed the repairs, and sprayed gelcoat. Put the engine back on, and now it looks like this:

go to the website for specifics on how to do your transom. In short, you will need to grind back the gel around the cutout, glass it properly inside and out, then pour your seacast. Actually, almost exactly what I had to do, with a little more glass. Read up on the website for the details.


08-19-2007, 09:20 PM
Jim this what I did;

1. Cut down the back to get rid of the gunnels and get a gap big enough for your motors.

2. My boat is solid glass remember. Then I ground the paint and shine off the glass.

3. Made a template for the back after cutting out the stringers. I had to make a template
cause I left two original stringers in.

4. Trace cut test fit etc.

5. Rough up the wood (3/4'' arc good one side plywood) with a grinder-just a little to help the fiberglass(fg) adhere.

6. Mix up some polyester resin (its good have a buddy help you with this cause one guy needs to mix while the other guy paints on resin).

7. Then I took some 1.5oz FG mat laid it on after coating the wood.

8. Coated the mat. (good to have a buddy again cause if you have a wide boat it will fall off the wood so have a friend to help hold it)

9. Get the bubbles out

10. Put some FG roving 24 oz on the already wet mat. Get the bubbles out etc.

11. Then put a final piece of 1.5oz mat on it and place it against the transom which needs to be painted in resin.

12. Uses clamps to hold it in and if you have a big bend we drilled holes in it and put bolts through it to hold it back.

repeat this three times until you have 3 layers of plywood on the transome and then use the 1.5oz, roving 1.5oz FG sandwich technique on the outside layer of the last piece of plywood.

Let each layer of plywood dry before you add another. Then grind the shine off the glass before you add the other layers.

Then, yes theres more, after the glass dries and between each coat put putty in the coners and lap some glass up on the side. Heres my little picture LOL...

08-19-2007, 09:21 PM
I was on their site, there is an overwelming amount of info on there.

I'll try to sort through it again, I was just hoping for the short answer:D

08-20-2007, 08:02 AM
1.5 roving is not really a woven mat. Its just fiberglass stands that are somehow held together. Its thin and pulls apart really easy when wet.

Basket Case
08-20-2007, 04:03 PM
Its just chopped mat, strands of fiberglass chopped 2 to 3 inch long then pressed together it comes in rolls from 6" to 60 " some use 3 oz mat for the final it give a little more glass to grind smooth before you gelcoat


done workin
08-23-2007, 06:59 AM
What is the difference between finishing off the fiberglass work with Gel Coat versus sanding then priming and painting with something like AwlGrip or Interlux or any of the other paint systems available.


One better than the other?