Any Transom experts here. I have a Transom Rebuilding Question.

[1985 Century Mustang]

I would not use pressure treated. Regular exterior grade plywood works fine.

Too many potential problems with PT wood, such as interaction with any fasteners/thru-hull fittings or problems with the resin sticking to the wood. Not worth the risk, IMO.

Thank for that.

 

[Scott06]

Can u resend the link, I can't click on it, its a dead link.

| Mercury Marine

Manufacturers of outboard motors and MerCruiser inboard engines, with over 4000 dealers in the United States.

www.zmm.ca

not sure why the pdf link didnt work ...the drawing is the first link on this page Alpha Gen 2 1992-2001

 

[1985 Century Mustang]

Can anyone advise what resin I need to use on the plywood transom. Resin or Epoxy Resin, I'm confused about the both of them. Is epoxy resin better than just regular resin?

 

[todhunter]

Just go with layup polyester resin like 435 from US Composites. Epoxy is more expensive, you can't tweak the catalyst to speed up / slow down the cure, and your boat was originally built with polyester. Epoxy is stronger, but the extra strength isn't needed in a rebuild.

 

[1985 Century Mustang]

Just go with layup polyester resin like 435 from US Composites. Epoxy is more expensive, you can't tweak the catalyst to speed up / slow down the cure, and your boat was originally built with polyester. Epoxy is stronger, but the extra strength isn't needed in a rebuild.

Do I need to purchase a hardener also? And what would the estimated curing time be if not?

 

[matt167]

Can anyone advise what resin I need to use on the plywood transom. Resin or Epoxy Resin, I'm confused about the both of them. Is epoxy resin better than just regular resin?

That’s a complicated question and answer. Epoxy is superior BUT it is not the most cost effective or required and can actually complicate things… your boat is polyester resin so

Do I need to purchase a hardener also? And what would the estimated curing time be if not?

MEKP is the hardener and it usually is included. It is required. Cure times vary depending on temp, humidity and how much hardener you use

 

[JASinIL2006]

Polyester resin uses MEKP as a catalyst. MEKP is nasty stuff, so handle with care.

 

[todhunter]

Do I need to purchase a hardener also? And what would the estimated curing time be if not?

It won't cure without the MEKP. As said above, it should be included with your purchase. Make sure you buy laminating (umwaxed) resin so you can do several layups without sanding. Honestly, based on the questions you are asking, I recommend picking up the phone and calling US Composites. They are friendly and helpful. And/or, you should watch some of the older Boatworks Today videos on YouTube, and the FriscoBoater SeaRay video series on YouTube.

 

[1985 Century Mustang]

I removed the rotted center transom down to the gel coat. The transom on the port and starboard are fine.

Question What is my next step, after I sand, vacuum, clean and acetone the center transom area, do I resin coat and use chop strain firstly in that targeted area of the gel coat (photo) below, and then plywood?
I will assess the stringers etc, I just need to know if I should use some chop strain and resin first before I do the 1 1/2 plywood. Your thoughts, thanks.

 

[JASinIL2006]

First of all, you really want to have good clean, fiberglass, similar to the pink suction on the left side of the keyhole. I’m not sure you’ll get good adherence to that stuff that’s sort of a light white color on the right side of the keyhole.

The standard approach would be to next prepare a piece of plywood to the desired thickness, usually by gluing together two pieces or by using thickened resin between two pieces of plywood to obtain the desired thickness. I used Titebond III to glue together the two pieces of plywood in my transom. after you dry, fit the plywood transom piece to make sure it fits, then you create a large batch of thickened resin with fiberglass strands (called peanut butter, due to its consistency) and use it to glue the plywood transom core to the hall.

The plywood transom core needs to be carefully clamped to make sure the flatness of the hull around the keyhole on the outside of the boat is maintained.

If you’re interested, I go into a fair amount of detail (with pictures) on this process in my restoration thread, starting about post number 50. The link to my thread is in my signature below. My transom is shaped a little differently than yours, but the procedure should be pretty much the same.

 

[Chris51280]

mine looked the same. you need to grind a bit more so the 1708 can wrap around and hold on to something. the "beanut butter" mix will fill the voids and adhere well to it. make sure you do a couple dry fits with the double plywood glued together. then make sure it will be parallel to the outside

 

[1985 Century Mustang]

To marry the two pieces of 3/4 " ply for the transom, is marine glue good such as titebond 3, or should I use resin and chopstrain to bind them? I have been reading good feedback on the titebond 3, A shout out to @JASinIL2006

 

[Chris51280]

yes, titebond 3 is the way to go

 

[JASinIL2006]

When I was trying to decide, I came across some steam/soaking tests of glues, and the glue that bonds the layers in exterior plywood failed before Titebond III did. It's more than sufficient.

You could use 'peanut butter' but it's much more of a pain, and for this application, it really doesn't have any advantage.

 

[1985 Century Mustang]

After I sand the transom and acetone it, should I do a light coat of just regular polyester resin? It could use some support in my opinion. It couldn't hurt or could it?

*And would the peanut butter mix adhere to it, if I do a light coat of resin to the transom first. Your opinion. Thanks

 

[Chris51280]

thin coats of resin don't cure very well and there is no advantage over using PB and then clamping the plywood down so the PB will squeeze out on the side. use the squeezed out PB to fillet and blend the valleys. This will give a good transition for the 1708 to adhere to

 

[JASinIL2006]

After I sand the transom and acetone it, should I do a light coat of just regular polyester resin? It could use some support in my opinion. It couldn't hurt or could it?

*And would the peanut butter mix adhere to it, if I do a light coat of resin to the transom first. Your opinion. Thanks

If you're talking about a coat of resin on the inside of the hull, I don't think that gains you anything. I think you're better off leaving the inside of the hull rough; it will have more tooth for the peanut butter to grab onto.

I do think there is value in skinning your transom core with fiberglass, though. I encapsulated mine with CSM before installing to make sure it was protected against any contact it might have with water. For that, it is good to wet out the wood with a coat or two of resin. (I went a little light on MEKP so the resin would really soak into the wood before 'kicking off'. That helps avoid air bubbles under the fiberglass later on.)

Just make sure you wipe down the hull and the transom core with acetone right before you apply the peanut butter. It is highly recommended you do some 'dry runs' with the core and your clamps to make sure you can handle everything quickly enough before your thickened resin hardens.

 

[1985 Century Mustang]

When I remount the gimbal housing back into the newly repaired transom I noticed the gimbal bolts are on an angle. Do I drill the transom bolt holes with that same angle? I saw a video awhile back but can't remember the YouTube vide. I watched. Thanks

 

[Chris51280]

yes

 

[1985 Century Mustang]

yes

Is there a proper way of doing this? And what angle would it be. Thanks.