Transom rebuild advice sought

[Aquaboy]

Hey all. Need advice on building a new full transom on a 1974, 22-2. The existing transom is in good shape without water damage. Is it necessary to remove the existing half transom, or is it possible to add to it?  I understand that adding knees from the stringers is a must What is the best method and recommended materials?

Planning on hanging a Porta bracket and 175 Suzuki. Thanks in advance for advice.

[RickK]

I don't think I would even consider going through the process without the transom being one solid core.

[gran398]

As Rick recommends you definitely need one solid laminate.

Leave the existing back piece of transom fiberglass on, remove the plywood and inner glass, and build to it.

Welcome aboard

[Aquaboy]

any preference between top grade marine plywood versus coosa board? How about Seacast?

[pete]

They are all acceptable methods of repair,the SeaCast method can be done without removing the transom skins,so it may be a little more DIY friendly,any method,done correctly will result in a good repair.

[TikiDoc]

If you have never done a lot of fiberglass work, the Seacast is a good option.  I redid my old Wellcraft transom with Seacast and it came out nice, but not perfect cosmetically.  My transom had been cut down to 20", so I raised it to 25".  Not as much work as a full transom, but conceptually similar.  I did mine with the outer skin off, as the inner skin had molded boxes on either side.  I built up the skins from the outside in after beveling the glass at about 8:1 (masonite mold, PVA release, gelcoat, then glass).  Once the prep is done, the Seacast is actually very easy to use.  I was very meticulous about removing the old wood, then degreasing with acetone.  The transom is unbelievably solid.  Exterior glass job OK.  It looked perfect (with the primer coat) until I painted it red.  A dark color really emphasizes any tiny imperfection in the glass finish.

[kaptainkoz]

I am going to do my transom on my 1979 246ccp in the next few months and I am sold on the seacast method. I plan on removing the transom from the inside, rebuilding the inner skin and pouring Seacast. I will not be disturbing the exterior. I like that the material is impervious to water and will basically be the last transom the boat will ever need. I also like that I will not have to seal every little screw hole against water reaching the core because, unlike ply, the core is waterproof. It is also a bit lighter and stiffer than ply and the process is easier than ply. The downside is that it is much more expensive than doing ply but its so worth the peace of mind. I am also planning on doing the gas tank cover with the "self leveling" version of seacast. I will report the step by step on here as it happens.

[dbiscayne]

Lighter?
Than plywood?  Pretty sure it's a little heavier.

It is a little easier & definitely won't ever have to worry about water damage.

[kaptainkoz]

Dbiscayne, that's what I thought when I first heard that, but what they claim and what read from regular guys like us is that the finished product is about 15% lighter. Keep in mind the amount of glass and resin a plywood transom requires. So its not just the weight of the boards alone that they are counting. They claim the the finished product ends up lighter. I revisited my notes and it turns out it isn't as expensive as I remembered. Before shipping it will be about $700 to pour a regular 246 CCP transom. I'm closing mine off and pouring the gas tank cover with the self leveling, so I'm looking at about $1,500 for everything before shipping. Seacast also sells bars and blocks of the same material, so spacing out the cavity with blocks of Seacast is the trick. I will also cut blocks and clamp them down to hold down the gas tank cover so it lays perfectly flat.  I'm looking forward to making this all happen aroud Labor Day.

[dbiscayne]

The diff in glass layup is almost nothing.
Keep in mind with a plywood transom the wood is providing the strength, the glass & resin are there to seal it more than to add strength.

Not trying to put down the pourable mat'l though its good stuff when done right just like everything else, just didn't want anyone thinking they're going to shed weight by using it.
It typically adds some but not much, works out to 53lbs/cf vs about 35 for marine ply.
Most people remove the wood from their transom & pour in the mix, without removing any glass.