transom replacement 21 ft alum boat

[Ken G]

Re: transom replacement 21 ft alum boat

I've used West System epoxy on both transoms I've done on aluminum boats. It works very well to glue the two pieces together. Both were done with marine plywood and I broke apart some sample pieces afterward and the plywood failed rather than the epoxy joint. The cloth on the Starcraft transom wasn't really necessary for strength but it was added to help seal the wood and also add a little thickness as the new transom was slightly less than 1 1/2" thick.

The fiberglass boat I'm currently working on, and using, I used exterior grade plywood and added some wood flour to the epoxy to thicken it slightly to help fill some voids as the BCX is rougher than the marine plywood. I've also been using a different brand of epoxy which is much more economical than the West System.

You can get the pink and blue foam board at least 2" thick at the big box stores and yes it is expensive. The white 2" foam board is a lot cheaper but it is a little coarser but it still floats. My Starcraft had big blocks of real coarse white foam blocks when I removed it. I scavenged some white foam blocks from the local hardware store for free. They are about 12" x 12" x 16". The store sells utility trailers and the trailers are stacked with these blocks when shipped in.

 

[jspano]

Re: transom replacement 21 ft alum boat

I've also been using a different brand of epoxy which is much more economical than the West System.

do remember the name?

 

[Ken G]

Re: transom replacement 21 ft alum boat

Yes but I probably can't post it here. I sent you a PM.

 

[jspano]

Re: transom replacement 21 ft alum boat

well i got all the old transom out and cleaned all the alum.
i am coating the inside alum skin with fiberglass
i will start to fig the plywood i need to match the thickness looks like 1 5/8 total.
i plan on appling the resin and cloth and the clamping them together using 2x4 as clamps.
after it cures i plan on coating the whole piece with fiberglass before installing it in the boat... hoping for strenght and water proof.

i need to get the large alum bracket(from the floor to the transom) welded. (small crack on 1 side and an ear came off on the other. will seek out a pro for that.

then on to the floor....

 

[ezmobee]

Re: transom replacement 21 ft alum boat

Sounds good. That transom should outlive you if you are careful with sealing anything you drill through it in the future. By the way, that bracket you are talking about having welded is called a knee brace.

 

[jspano]

Re: transom replacement 21 ft alum boat

i spoke with a gentleman at a local marina and he suggested sizing the wood first with resin (no harder) and acetone first. letting that cure and then bonding the 2 pcs together with the resin, harder, and the cloth.

any input

i'm trying a small pc of ply wood first

joe

 

[jspano]

Re: transom replacement 21 ft alum boat

also when csrewing the new floor down what kind of screws should i use

 

[ezmobee]

Re: transom replacement 21 ft alum boat

A number of us are using rivets. On my Jupiter I used the tan deck screws from Home Depot. They seemed to work fine and I may very well use them again on my SS project.

 

[jspano]

Re: transom replacement 21 ft alum boat

what material were the screws made of?
just wondering cause i read about dissimilar metals

 

[ezmobee]

Re: transom replacement 21 ft alum boat

I think steel http://www.deckmatescrews.com/ I didn't notice any issues with them in the 5 years I had my last boat, and I didn't notice any issues with the stainless screws I just removed from my current project. Both the screws and the aluminum seemed to be in perfect shape.

 

[jspano]

Re: transom replacement 21 ft alum boat

i had a 115 johnson on the boat i might even try the repair on that(but that's another job).
do all the motors have the same bolt pattern.
would a 90 hp from another company match.
cause i'd like to use the engine mount holes as addition clamp spots

thanks again

joe

 

[Bob_VT]

Re: transom replacement 21 ft alum boat

You should find the mounting holes for most outboards today are matched to BIA standards and the holes should match.

 

[mikastorm]

Re: transom replacement 21 ft alum boat

I had a 90, older motor, not sure what year but it was very large.
I too was worried about the holes matching up to my 84 , 75hp evinrude.
But no fear, they matched.
I have a 16ft. Sylvan but everything seems to match the Star Craft design.

Be sure to get the foam out from under the stringers to allow for better drainage.

 

[Andy in NY]

Re: transom replacement 21 ft alum boat

I'll comment on what I know....

#1 I would do a single U and fit it in. That should be strongest transom. I hadn't actually seen an SC with a pieced transom before yours.

mine was pieced...

see how it keeps going straight? i had already removed the triangle piece...

also when csrewing the new floor down what kind of screws should i use

i used stainless steel screws. they are a bit more expensive, but there is zero chance they will react to the aluminum.

 

[jspano]

Re: transom replacement 21 ft alum boat

[Be sure to get the foam out from under the stringers to allow for better drainage.
/QUOTE]


how do you do that???

 

[mikastorm]

Re: transom replacement 21 ft alum boat

You may not have this issue but mine did. What happened was when they poured the foam it expanded and sealed under the stringers. I had to use a small puddy knife and a small pry bar to pull it all out.
I believe this helped rot the floor. The drainage was closed off.
Anyone else see this?

 

[Andy in NY]

Re: transom replacement 21 ft alum boat

You may not have this issue but mine did. What happened was when they poured the foam it expanded and sealed under the stringers. I had to use a small puddy knife and a small pry bar to pull it all out.
I believe this helped rot the floor. The drainage was closed off.
Anyone else see this?

i can say that on mine there was so much junk under the deck that the drainage was clogged and there was a good amount of standing water under there. thats why its not recommended to use poured foam in a tinny.

 

[timfives]

Re: transom replacement 21 ft alum boat

As convient as poured foam may seam, if you ever have to do other work on the boat, you will curse yourself. Further it will clog any drains and thus the boat / floor will hold water.

I've just spent a bunch of time removing the factory foam, and will not be using it again.

Tim

 

[timfives]

Re: transom replacement 21 ft alum boat

oh also i used a sharp hatchet and heavy duty putty scrapper to remove the foam. If it is dry it will come out pretty easy, if wet, welcome to the 4th level of Dante's inferno.

Tim

 

[jspano]

Re: transom replacement 21 ft alum boat

so even if the foam looks good you think i should reolace it???

all of it or just replace the middle section to aid in draining

also what thicknes wood should i use for the flooring( i plan on sealing al 6 sides)