Transom Replacement

By Dave Casper

 

When I bought my Vegas a few years ago, I knew the transom and parts of the floor were in bad shape and would need to be replaced. In this article I will describe how I went about replacing the transom. In the future, I will write about the floor replacement. It should be kept in mind that the procedure I used was based on the condition of my transom and may not be the ideal method for others. Also, I am sure there are others who have done this a different way and whose procedure could very well be better than mine. At least this will give someone who is going to replace their transom an idea of where to start.

The first thing I did was to remove the aluminum rub rail along the top of the transom. The outer fiberglass skin on my transom had partially delaminated from the wood so I decided to remove this skin for reuse. I did this for two reasons. First, by reusing the skin, it would be easier and faster to get a smooth, even finish on the transom. And second, I would be replacing the area that has the hull’s serial number on it.Transom1.jpg (46638 bytes) I used a Moto Tool with a cutting wheel to cut through the fiberglass layer around the perimeter of the transom, cutting approximately 1- inches in from the sides and bottom. I then peeled off the skin, carefully using various tools to pry it off in areas that hadn’t delaminated. I have read that a heat gun can be used to help peel the skin off. I then took a Sawzall and cut through the transom and the inner fiberglass layer. I cut a rectangle about 1- inches from the bottom, about 6 inches from the sides, and along a line BELOW the bottom of the splashwell. This step could have been deleted – it was just a faster way of removing the old transom wood. Then the tedious process of removing the rest of the wood began. I used chisels to remove all of the remaining wood and to smooth the surfaces where the inside edges of the transom wood had butted up to the fiberglass. At this stage I had most of the inner fiberglass layer remaining for the new wood to align and attach to. Also, the 1- inch perimeter remaining of the outer fiberglass layer provided a "pocket" to place the new wood into. If this pocket was not there, fiberglass cloth would have had to been layered from outside the transom around to the sides as well as the bottom. This would have required much more time and effort to fair into the rest of the hull. The way I proceeded retained the original fiberglass thickness on the outside of the transom, and a thicker, reinforced fiberglass layer on the inside.

For the new transom I used three layers of inch marine plywood. This would provide the original transom thickness of 1- inches. For additional strength, each layer would have the grain rotated 45 . To make installation easier, the first two layers would each be in two pieces, the third layer would be in three pieces. The supplies I needed for the transom installation were:

 

West System #105 resin with #206 slow hardener (to allow the longer working time needed)

West System #404 high density and # 406 colloidal silica fillers

West System #810 fillable caulking tubes (3) and caulking gun

Fiberglass cloth: 6oz woven

1-inch stainless steel wood screws

 

After carefully measuring the dimensions needed for the first, or inner layer, I cut the wood to size leaving it slightly wider than its final dimension. This was done to compensate for cutting the piece in two. This cut was not made in the middle – it was cut about 1/3 from the end. Also important was that Transom2.jpg (46186 bytes)this cut was a scarf joint at about a 10:1 ratio. The wood was trimmed until it fit in position properly. At this point, with the first layer in position, I took some scrap pieces of the plywood, doubled them up to simulate the last two layers, and placed them around the edges. This was done to make sure the pocket was trimmed out enough for all three layers to fit snuggly. The pieces of scrap would also hold the first layer in position while the epoxy dried. Before the epoxy for the first layer was mixed, I made sure that all the fiberglass surfaces were scuffed with sandpaper, and all the loose material was removed. The resin and hardener were mixed and then the mating areas were "wetted out". This included the remaining inner fiberglass skin, the inside of the pocket where the edges of the wood would butt up to, and the side and bottom edge of the wood as well as the surface area of the wood that would attach to the inner skin. The epoxy mixture was then thickened with a 75% #404 and 25% #406 mix to achieve a consistency of catsup. This mixture was thinly applied to the face of the wood and the fiberglass skin. The epoxy was then further thickened to the consistency of mayonnaise. This mixture was then put into one of the caulking tubes. A thick bead of this mixture was then applied along the sides and bottom of the pocket. This bead needed to be thick enough to fill any gaps and voids. The wood was then placed in the pocket as previously tested. The excess epoxy that was squeezed out along the edges was removed. Wax paper was then placed in the pocket and the double up pieces of scrap wood were placed in the edges to hold the first layer of the transom in place. The top area of the wood was also clamped to the back of the splashwell. After the epoxy had dried, the second layer was installed basically the same way. The only differences being that the scarf joint of this layer would go to the opposite side of the centerline than the first. Also, screws would be used to help attach the two layers to each other. The third layer was installed the same way with one important difference – the wood was cut into three pieces with the center piece being about 12 – 14 inches wide. This allowed the two end pieces to be installed first and then the center piece. The final layer is held in place by the screws, the pocket, and clamping along the top. A couple of notes:

Any cured epoxy must have it’s surface scuffed and cleaned to remove amine blush before another coat is applied or proper bonding will not occur.

All surfaces should be cleaned with acetone before bonding.

Enough epoxy must be applied so that some will squeeze out of the joints

Do not place the screws where bolt holes will be drilled.

Once the surface of the third layer of theTransom3.jpg (90455 bytes)transom had been sanded flat and smooth, the outer skin was re-attached. The edges of both the skin and the pocket were beveled at about a 10:1 ratio. The back of the skin was sanded smooth and then both it and the wood were cleaned. The next step was to wet out both surfaces with epoxy. Then the mixture was thickened to a catsup consistency with the same ratio of fillers and applied to both surfaces. The skin was placed in position and clamped. To clamp the skin down, I placed a large piece of plywood over the skin with wax paper between the two. Then I used an assortment of 2x4’s and clamps of various lengths to hold the skin flat and in position. After the epoxy dried, the beveled area, any old holes such as bolt holes, or any gaps along the top edge were filled in first by wetting out and then by thickening the mixture to the mayonnaise consistency.

Finishing the inside of the transom was completed by scuffing and cleaning the gelcoated surfaces anywhere fiberglass cloth was going to be laid. The fiberglass cloth and corresponding surfaces were wetted out with epoxy. The first few layers of cloth were placed over the bare transom wood to bring its surface more even with the surrounding area. Multiple layers of cloth were then applied over the whole transom and extending forward about 10 inches on the sides of the hull. The transom to floor joint was also covered with cloth. To prevent stress cracks in the splashwell, the transom was not fiberglassed directly to the bottom of the splashwell. When this step was completed, bolt holes were drilled and sealed and the outside of the transom was sanded smooth. I also further reinforced the transom by installing two vertical braces. These braces were made out of marine plywood and extended about 6 inches forward from the transom right up to my gas tank. They were placed to the outside of the lower engine mounting holes – leaving extra room for a reinforcing plate. The height of the braces were 1 inch short of the splashwell. Before these braces were installed, a notch was cut in the bottom rear corner of each one to allow water to drain through them. The wood was then sealed with epoxy and the braces then attached to the transom and floor with epoxy and cloth.

Painting the transom inside and out, and then reinstalling the aluminum rub rail completed the transom replacement. When mounting the engine, stainless steel reinforcing plate was installed on the inside of the transom, the inside of the splashwell, and on the rear of the transom covering an area larger than the jack plate.

Transom4.jpg (72250 bytes)

 If anyone has questions, please feel free to e-mail me at gnhhydro@aol.com

 

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