Transom Replacement Material Options

[wmk0002]

Just got back from the lumberyard. Bought a 3/4" sheet of BC plywood for $47 along with some 5/16"x24 ipt bolts to pull the flywheel on an old 9.8 Mercury.

Gonna get some epoxy from raka ordered up this evening. While at it I'm going to get some extra to replace some of these old patch jobs done on this boats hull. Was going to get the thin epoxy for the the transom sealing but do I need a thicker viscosity epoxy for aluminum patch work? I've been somewhat lucky and not had to deal with leaks in aluminum hulls until now.

 

[CedarRiverScooter]

I chop up fiberglass cloth (with scissors, takes a few minutes) to thicken epoxy for patches. Great for filling holes too.

 

[idruthrbfishin]

Don't use fiberglass resin. I used it on a modified V many years ago when I was young and uneducated LoL. While it might hold up for a while, it is not the right type of polyester resin for this application. Use a 2 part epoxy designed specifically for boat transoms, it will last much longer. I have used "Gluvit" with excellent results. Others will tell you West Systems makes a good product as well.

Fiberglass resin WILL peel off plywood ... not IF, but WHEN ...

Best bet, price and value in 2-part mix epoxies is www.raka.com. Figure out your square footage and call Mike or Larry and talk to them. Simple 2-to-1 mix, regardless of how much mixed (at least with their standard resins). Works as good as any non-specialized West Systms product at 1/2 to 2/3rds the price, and with no need for expensive mix pumps.

Wow, their (Raka's) prices are great! Wish I knew that before I bought 3 quarts of Gluvit at $65/quart!

 

[ClemsonAlum]

I used HDPE board for my old boat. Sandwiched two 3/4" pieces of it with aluminum in the middle. Stainless bolts. Kind of like cutting board material.

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[DaleH]

I used HDPE board for my old boat ... Kind of like cutting board material.

IMHO, HDPE is not a good choice for everyone, nor for bigger motors ... but well ... glad if it worked OK for the poster.

Weight - It weighs TWICE as much as plywood of the same thickness.

Structural Specs - HDPE is not a recognized structural material; read up on how new decks need closer joists and can't support the weight wood planks can. It is also far weaker in bending, deflection (by a large factor!), and shear than plywood. Also bends like spaghetti in warmer temps!

I've seen a 30hp Johnson warp the stern of a Lund 14SV that was re-transomed with HDPE, bent the livin' snot out of it above the knee ... thusly I would not recommend anyone use HDPE as a transom core material alone. I've seen 1/2" pieces added to a stern, but they still had wood cores.

 

[ClemsonAlum]

Yeah, I agree it depends on what size motor your hanging on. I can say it worked excellent with my 1436 and 9.5 Evinrude. No flex. Will never rot or rust.

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[idruthrbfishin]

I used HDPE board for my old boat ... Kind of like cutting board material.

IMHO, HDPE is not a good choice for everyone, nor for bigger motors ... but well ... glad if it worked OK for the poster.

Weight - It weighs TWICE as much as plywood of the same thickness.

Structural Specs - HDPE is not a recognized structural material; read up on how new decks need closer joists and can't support the weight wood planks can. It is also far weaker in bending, deflection (by a large factor!), and shear than plywood. Also bends like spaghetti in warmer temps!

I've seen a 30hp Johnson warp the stern of a Lund 14SV that was re-transomed with HDPE, bent the livin' snot out of it above the knee ... thusly I would not recommend anyone use HDPE as a transom core material alone. I've seen 1/2" pieces added to a stern, but they still had wood cores.

Agreed. I had a buddy try to talk me into using HDPE for my Grumman deep vee w/ 60 HP Evinrude. The stuff is just way too flexible for a heavier motor. Might work OK for the posters 9.9, I wish him well, but I went with good ol' tried n true plywood.

On that subject, everyone always says, "You HAVE to use MARINE plywood for your transom!" (because it uses waterproof glue) My question is, since I'm encasing it with 2 good coats of epoxy, why does it matter whether the glue is waterproof? That epoxy coating is impenetrable! LoL :lol:

Plus, the original plywood was not epoxy coated, and it lasted for 30+ years! If this one lasts that long, someone else can replace it next time. I'll probably be worm food by then.

 

[CedarRiverScooter]

Exterior grade plywood uses waterproof glue, same glue as marine.

The diff between X & marine is that marine doesn't have any knot voids.

 

[bplayer405]

Got the chance today to work on a friend's jon boat that needed a new transom. He wanted all aluminum and bought some 1.5" x 3" square tubing to replace the plywood. Turned out pretty good and is quite strong! Gonna add a piece of plate to the inside where the outboard mounts.

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