Transom rebuild questions

[arcee1951]

There are a multitude of examples, and I've spent hours reading them, but it appears that it would take even more hours to answer a couple of simple, I hope, questions.

I have a 1981 tinny Starcraft, and have removed the rotted transom. I'm going to be using ACX plywood, as that is the only thing available in this city.

1) I can't find any marine epoxy within 100 miles, and that is at a wholesale warehouse. My new transom board will be about 20x70. How much epoxy would I need? Obviously, this is a first for me, and the stuff seems to be pretty expensive.

2) I saw somewhere, a discussion on the use of SPAR urethane. I can get that locally. Would this be an acceptable alternative?

3) In either of the above cases, should a topcoat of paint be put on? If so, what type of paint?

4) I also saw a thread stating that JB Weld would work for filling holes in the back skin of the transom. It looks as though there has been at least one engine swap, leaving 4, I didn't measure, but guessing 3/8" holes, along with 6 other smaller holes. The thread said to put tape on, and fill the hole. I didn't see where it said what type of tape to use? Leave the tape on, or remove it? Other than welding, is there another more acceptable method of plugging the old holes? I also read that a person should partially drill a larger hole for the JB to fit into, which makes sense.

5) How tight should the new board fit in the hole? Should it be a tight fit, or is having a little wiggle room ok?

That's probably not all I'll have for questions, but should get me to the next sense. Great site!

 

[jbcurt00]

Re: Transom rebuild questions

Which 1981 SC?

1) There's nothing else in your rebuild that you might use epoxy on? US Composites is popular for both tin & fiberglass resto's. In SD, there may be other options available online. Depends on what else might benefit from the epoxy.

2) Spar Urethane can be used but will require more frequent maintenance then epoxy. Another option would be boiled linseed oil, mineral spirits & varnish/polyurethane in 3 equal parts. Applied generously until the wood will no longer take any more, after several wet applications. Wipe the pooling unabsorbed mixture off, allow it to thoroughly dry, then topcoat. Porch paint can also be used. It's all about cost now vs longevity & cost later....

3) Epoxy requires a UV protectant to be applied to any that will be exposed to UV. Spar Varnish, oil based enamel, porch paint, among others....

4) Cover the hole w/ duct tape on 1 side. Generously fill the hole w/ JB Weld, leaving a little extra above the surface, it'll shrink some. Once dry, sand smooth. I wouldn't make the hole larger, but you want to make sure you've got good material for the JB Weld to 'grab'......

Welding isn't the best choice unless you are extremely 100% confident in the welder's ability to work on aluminum. Aluminum can be work hardened/fatigued when welding, which can lead to larger problems later. Some have had great success.

5) Not so tight as to scrape your epoxy/paint/spar off, but not loose either. Firmly seated between the rubrails/gunwale & just to the top of the aluminum transom skin. The metal & plywood will expand & contract at different rates. A bit loose before being encapsulated w/ epoxy, spar, etc can then be fairly tight once coated.

2-3 coats of epoxy per side, all edges done w/ every coat, they'll get 4-6 coats (then 2 coats of spar/paint per side, edges w/ every coat)

VS

4-6 coats of spar per side, all edges w/ every coat

Best of luck w/ your project,

Welcome to iboats dry dock, tin division

 

[arcee1951]

Re: Transom rebuild questions

Which 1981 SC?

1) There's nothing else in your rebuild that you might use epoxy on? US Composites is popular for both tin & fiberglass resto's. In SD, there may be other options available online. Depends on what else might benefit from the epoxy.

2) Spar Urethane can be used but will require more frequent maintenance then epoxy. Another option would be boiled linseed oil, mineral spirits & varnish/polyurethane in 3 equal parts. Applied generously until the wood will no longer take any more, after several wet applications. Wipe the pooling unabsorbed mixture off, allow it to thoroughly dry, then topcoat. Porch paint can also be used. It's all about cost now vs longevity & cost later....

3) Epoxy requires a UV protectant to be applied to any that will be exposed to UV. Spar Varnish, oil based enamel, porch paint, among others....

4) Cover the hole w/ duct tape on 1 side. Generously fill the hole w/ JB Weld, leaving a little extra above the surface, it'll shrink some. Once dry, sand smooth. I wouldn't make the hole larger, but you want to make sure you've got good material for the JB Weld to 'grab'......

Welding isn't the best choice unless you are extremely 100% confident in the welder's ability to work on aluminum. Aluminum can be work hardened/fatigued when welding, which can lead to larger problems later. Some have had great success.

5) Not so tight as to scrape your epoxy/paint/spar off, but not loose either. Firmly seated between the rubrails/gunwale & just to the top of the aluminum transom skin. The metal & plywood will expand & contract at different rates. A bit loose before being encapsulated w/ epoxy, spar, etc can then be fairly tight once coated.

2-3 coats of epoxy per side, all edges done w/ every coat, they'll get 4-6 coats (then 2 coats of spar/paint per side, edges w/ every coat)

VS

4-6 coats of spar per side, all edges w/ every coat

Best of luck w/ your project,

Welcome to iboats dry dock, tin division

Thanks, jb. I'm not sure what they would call this Starcraft. It's basically a fishing boat with an open bow and one console, possibly homemade.
1 )I pulled up some of the carpet in front and rear of the boat, and the wood looks good, so I don't think I'd have any other use for epoxy. Would a quart be enough, if I can even find that?

2) The boat will be put in the garage in the summer, and probably covered in the winter. That being the case, what are you thinking for "more frequent maintenance", in length of time? When you mentioned the linseed oil, mineral spirits and varnish, were you talking about mixing them all together and applying, or do each one individually? Would this process be after gluing the 2 pieces together? Would that effect the type of glue I should use?

3) Gotcha.

4) It sounds like JB Weld makes different types? I've never worked with the stuff, but am guessing that it must not be too runny, or a person wouldn't be able to keep it from running out of the vertical holes?

5) Gotcha

Thanks.

 

[jbcurt00]

Re: Transom rebuild questions

If you can find a mixed gallon volume of epoxy, that's probably the smallest, large volume you'll find. I've never seen a qt of epoxy sold, might be available somewhere. Epoxy is often sold in a gallon container that then has an appropriate volume of hardener in another container. If it's all mixed together at once, it'd be a total volume of 1.5gal w/ a medium speed hardener. Roughly 2 parts resin to 1 part hardener. I have bought epoxy that once mixed, in total, it yields exactly 1gal. I think US Comp sells the resin as a gallon so you'd have more then you need. It does have a shelf life, even unmixed.

I'd get whatever volume of epoxy you find reasonably delivered to SD. US Comp will probably be that source.

You mix the BLO, Mineral Spirits & Poly/Varnish together & apply the mixture to the already glued & cut to final shape transom plywood

You should check the transom wood frequently, no matter the finish you choose. But in harsh conditions (fishing in the rain, lots of strong UV exposure) you might need to scuff the transom plywood & reapply the poly/varnish twice a year.

Use epoxy 1st & then the spar urethane and it should still be inspected regularly, but I doubt you'd have to recoat more then once every couple of years even in harsh conditions.

Use a waterproof glue to glue the transom blank. TiteBond3, GorillaGlue (or other polyurethane based glue) are both good choices.

If you've used bondo, JB Weld is about the same consistancy once blended. In heavy globs it may run & sag a bit, but firmly pressed onto the tape backed hole, and skimmed about smooth, it won't sag out so much to sag off/out. Large defects may need a couple thin applications to build enough thickness to be slightly overfilled.

 

[Woodonglass]

Re: Transom rebuild questions

If you choose to seal your wood with the BLO, MS, Poly mixture make sure and soak it well. Really put a lot on and allow it to soak in and really coat the edges well. That's where the water will try to attack first. After a couple of hours wipe off any excess and then let dry for 48 hours preferably with ventilation and heat. I'd then recommend 2 coats of Rustoleum Pro Primer followed by 2-3 coats of Rustoleum Pro Oil Based Paint. Again Really get the edges coated well. If there are "Voids" in the edges fill them with a vinyl base wood filler prior to priming the wood. Anytime you drill into the transom you should always predrill the holes and then coat the holes and the hardware with a quality Marine Sealant such as 3M's 4200 or 5200.

 

[Watermann]

Re: Transom rebuild questions

I'm in the camp of the non-epoxy transoms. I used Titebond polyuerethane glue for the lamination of the 2 pieces. I then cut my transom and gave it a test fit with the bare wood. When convinced it would fit in without tearing up the finish, I marked all of the holes with a sharpie and on a flat surface drilled them straight through before the finish work.

After all the sanding was done and holes drilled out the entire transom pieces got the following treatment.

1. OIl base Zinser primer x 2 coats.
2. Oil based rustoleum enamel x 2 coats, maybe 3 coats if the wood sucks it up and it looks weak in spots.
3 Helmsman Spar urethane x 3 coats.

You won't believe how great that piece of wood will look when your all done. No toxic fumes and no "it's too soon to kick" of the resin to turn your batch into a hot rock. Also you would most likely need a gallon of the epoxy resin, 1 qt wouldn't do from what I've seen on here.

I made sure all of the holes were just a bit over sized for the bolts so I could get the spar down inside to soak into the wood. When installing the mounting bolts and screws I used marine silicone on them to seal it up.

If you do go with the $80-90 a gallon epoxy you will still have to cover it with spar, paint or both to hide it from the sun's rays so it doesn't degrade. Unless your transom is completely sandwiched between aluminum layers then your back to relying on spar and paint to keep your transom in good shape so the maintenance is the same.

 

[kfa4303]

Re: Transom rebuild questions

It sounds like the boat won't be getting too much wear and tear in a given year and the fact that it's garage kept will help a lot too. That being said, I'd probably just go with the Spar for its cost and convenience. The epoxy would be nice, but it may not be worth getting shipped to SD for such a small amount. Shoot, I used several coats of Rustoleum Professional Oil Based enamel and it has held up quite well and I use my boat almost year round in fresh and salt water. It sits outside under a tarp in the heat and rain and is still going strong. Just curious, where does one boat in SD any way?

 

[arcee1951]

Re: Transom rebuild questions

It sounds like the boat won't be getting too much wear and tear in a given year and the fact that it's garage kept will help a lot too. That being said, I'd probably just go with the Spar for its cost and convenience. The epoxy would be nice, but it may not be worth getting shipped to SD for such a small amount. Shoot, I used several coats of Rustoleum Professional Oil Based enamel and it has held up quite well and I use my boat almost year round in fresh and salt water. It sits outside under a tarp in the heat and rain and is still going strong. Just curious, where does one boat in SD any way?

Lots of terrific info. I'm going shopping with a lot more knowledge than I had before. I may not buy anything, but I'll feel a little more comfortable. As far as boating in South Dakota, I won't be pulling the grandkids on skis, but my neighbor and I limited out the last two days on walleyes and northern pike. The walleyes were 2-4 lbs and the northern, were small, and about the same. We did nail one walleye that was 26", so probably 5.5 lbs. Perch and blue gill season starts in a couple weeks, after this nasty heat spell is over.

Thanks again.

 

[arcee1951]

Re: Transom rebuild questions

One other question, that I'm not clear on. It's been said to make sure that the new transom fits snug, but not so snub that we take the finish off. Is there anyway of guesstimating how much play to leave on each side? Thanks again.

 

[kfa4303]

Re: Transom rebuild questions

Who knew there were so many fish in SD? awesome! Glad y'all are having some luck this year. The boat will be a fun project for you too, but be warned it's addictive. These old tinnies are the best; they're cheap as chips, easy to repair and maintain with everyday tools and techniques and there were lots of regional builders back in the day, so there is lots of variety in styles and configurations from Jon boats to runabouts to commercial fishing vessels. Best of all, the same materials and techniques apply regardless of style. (No PT wood, Stainless Steel Hardware throughout, 3M 5200 for through hull fittings, seal any wooden components with epoxy/spar/quality paint).

 

[Watermann]

Re: Transom rebuild questions

One other question, that I'm not clear on. It's been said to make sure that the new transom fits snug, but not so snub that we take the finish off. Is there anyway of guesstimating how much play to leave on each side? Thanks again.

Does your transom have brackets on the port and starboard side for the transom wood to slide into? My SN didn't have the side brackets but my Chief does, probably because of the mammoth size of the I/O transom wood. If your asking how wide to make the transom and worrying about there being a gap between the wood and the sides then don't worry. Just get the side of the transom wood as close as you can without them touching the aluminum sides of the hull. If they touch then it will through vibration rub the finish off, gouge the wood and maybe give water a place to get a foot hold into rot later on.

 

[arcee1951]

Re: Transom rebuild questions

Does your transom have brackets on the port and starboard side for the transom wood to slide into? My SN didn't have the side brackets but my Chief does, probably because of the mammoth size of the I/O transom wood. If your asking how wide to make the transom and worrying about there being a gap between the wood and the sides then don't worry. Just get the side of the transom wood as close as you can without them touching the aluminum sides of the hull. If they touch then it will through vibration rub the finish off, gouge the wood and maybe give water a place to get a foot hold into rot later on.

Awesome!! Watermann, not really a bracket, but there is a channel, front and rear. If you go too close, you hit rivets on each end, so measuring is not perfect. One other thing I noticed, is that the rear ID of the boat, has rivets that stick out a quarter of an inch, and when you put the transom back, it will definitely make 2 marks all the way down. Maybe remove the ID plate and redo after the transom is in?

 

[Watermann]

Re: Transom rebuild questions

Awesome!! Watermann, not really a bracket, but there is a channel, front and rear. If you go too close, you hit rivets on each end, so measuring is not perfect. One other thing I noticed, is that the rear ID of the boat, has rivets that stick out a quarter of an inch, and when you put the transom back, it will definitely make 2 marks all the way down. Maybe remove the ID plate and redo after the transom is in?

Good idea with the plate, any little way to make thing's easier on you, drill them out and when you put the plate back on, you could use SS screws and sealer.

 

[arcee1951]

Re: Transom rebuild questions

Good idea with the plate, any little way to make thing's easier on you, drill them out and when you put the plate back on, you could use SS screws and sealer.

Thanks to everyone. It looks like I'm going with Waterman's plan. Everything was available in town here, except I haven't found the 5200 or 4200 yet, or the back splash drain tubes. I was actually able to find the Rustoleum in a color that is close to my back splash color. Today I'll start reassembly.

Today, I'll get the ACX cut and glued together. I'm guessing to glue it before cutting in the holes, and let it set for 1 day?
I'll start filling holes in the transom and back splash. Filling those 18 holes may help keep the transom drier. The guy that owned the boat before me must have thought he was going to fix it up, then gave up. He sanded some of the back splash down to bare metal, where the holes were, then quit. I've never painted aluminum before. Does it take a special primer before being painted?

I took a lot of pictures as I was tearing the old transom out, and most of that was done with spoon. Not really, but 1/2 of it was soaked with water. I'll look again today, but do the drain tubes go in at an angle, and if so, how do you find that angle, so I get proper drainage. I'll have to look for the tubes also.

Thanks again guys!!

 

[Bob_VT]

Re: Transom rebuild questions

Home depot sells 3m5200 in the glue section. Transom drains are available in the iboats store online Boat Parts & Accessories For Your Boat - iboats

 

[arcee1951]

Re: Transom rebuild questions

Home depot sells 3m5200 in the glue section. Transom drains are available in the iboats store online Boat Parts & Accessories For Your Boat - iboats

Thanks, Bob. Once again, being out in the boonies doesn't help. Sioux Falls would be the closest Home Depot, and that is 100 miles south of me. Getting material has been a bigger issue than building the transom. There is a Lowes about 50 miles south, but I haven't found a tube in town.

 

[Watermann]

Re: Transom rebuild questions

I've used the Rustoleum self etching primer to get the paint to stick, works great. Walmart has it and so does the car parts places.

I had to order my drain tubes for the splashwell. Some guys get the plastic ones so they don't have to worry about a flange tool needed to install the aluminum ones correctly. Just put the drain tube holes in through straight, not at an angle. They need to be at the same angle as the motor mount bolts which will be slanted outwards. Otherwise if they are off the same angle as the transom skin it would make it more difficult to seal them up on the outside. Hopefully you won't be using the spashwell and drain tubes a whole bunch when out on the water. The nice thing about the tubes is you can hold off on them and they can even be the last thing you put in.

As far as 5200 and 4200 goes, just know that 5200 is a gooey messy substance that takes days to cure up but when it does its permanent unlike 4200 which is just a 100% silicone, pretty much any "marine" grade silicone is the same at 4200. I've used DAP marine silicone and have had good luck with it. ACE sells the DAP and a bunch of other epoxy stuff too if you have one check it out, they also have Rustoleum Topside marine paint.

Edit: Good lord 18 holes!!! oh and yeah let it set at least a day before pulling the clamps and working on the transom.

 

[kfa4303]

Re: Transom rebuild questions

+1 it's pretty gloopy, but it will clean up with a bit of acetone/rubbing alcohol. Give it a true 24hrs to cure and you'll be good to go.

 

[arcee1951]

Re: Transom rebuild questions

I've used the Rustoleum self etching primer to get the paint to stick, works great. Walmart has it and so does the car parts places.

I had to order my drain tubes for the splashwell. Some guys get the plastic ones so they don't have to worry about a flange tool needed to install the aluminum ones correctly. Just put the drain tube holes in through straight, not at an angle. They need to be at the same angle as the motor mount bolts which will be slanted outwards. Otherwise if they are off the same angle as the transom skin it would make it more difficult to seal them up on the outside. Hopefully you won't be using the spashwell and drain tubes a whole bunch when out on the water. The nice thing about the tubes is you can hold off on them and they can even be the last thing you put in.

As far as 5200 and 4200 goes, just know that 5200 is a gooey messy substance that takes days to cure up but when it does its permanent unlike 4200 which is just a 100% silicone, pretty much any "marine" grade silicone is the same at 4200. I've used DAP marine silicone and have had good luck with it. ACE sells the DAP and a bunch of other epoxy stuff too if you have one check it out, they also have Rustoleum Topside marine paint.

Edit: Good lord 18 holes!!! oh and yeah let it set at least a day before pulling the clamps and working on the transom.

Did I say one more question? Sheez. I have my 2 pieces of plywood cut, so never mind about the thickness. I put both in, without gluing or clamping and had one heckvua time getting them back out. There is a little play from side to side, not much, but when both pieces are in the channel, it is tight. I'm thinking that maybe I should put a couple of screws in the two pieces and maybe clamp them, and mark and drill my holes out before gluing???? I'm afraid I wouldn't get the new transom back out to finish the prep work? I wonder if I shouldn't round the edges a little with a sander? Maybe it is the square edges that make it so tight. I haven't trimmed the tops down yet, so have about 8 inches sticking up, except on the extreme outsides.

 

[Watermann]

Re: Transom rebuild questions

Did I say one more question? Sheez. I have my 2 pieces of plywood cut, so never mind about the thickness. I put both in, without gluing or clamping and had one heckvua time getting them back out. There is a little play from side to side, not much, but when both pieces are in the channel, it is tight. I'm thinking that maybe I should put a couple of screws in the two pieces and maybe clamp them, and mark and drill my holes out before gluing???? I'm afraid I wouldn't get the new transom back out to finish the prep work? I wonder if I shouldn't round the edges a little with a sander? Maybe it is the square edges that make it so tight. I haven't trimmed the tops down yet, so have about 8 inches sticking up, except on the extreme outsides.

The way I did mine was a bit different, I cut the wood to the correct height and then final shape after gluing the 2 pieces of 3/4" together. I would glue them together, sanding the raw edges is always a good thing to keep from having run away splinters while handling the wood. You can always tweak the aluminum channel just a bit too, it's not going to hurt anything if it's just a tiny bit to allow the transom to slide in better. I know that those channels can create one heck of a mechanical bind on the raw wood.

I wouldn't drill out the holes before gluing and the final fit, it leaves room for a mistake.