Cracked top cap on my transom...*(progress update)*

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kenzy31

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Central Ontario
I noticed a crack right near my motor last week that concerns me (as any crack should). I did some searching around the site but didn't really find anything similar to mine. I'm looking for a reliable repair that I can hopefully do myself. That means no welding, but I can handle most other tasks myself or have someone close who can. At the end of the season I may also replace the transom wood, inside and out, but for now the crack in my main concern. Here are a few pics of the area in question...

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And the ID plate from inside the boat..

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I think the main thing to repair here is the transom. Fix that and you should be fine. I wouldn't bother working on the metal w/o replacing the wood first.
 
At a second look, it appears your transom is supported mostly from the outside, is that correct? Do you have a pic of the transom not so zoomed in?
 
I agree. The aluminum cracked because your transom is weak. Any repairs to the aluminum without fixing the wood base will only quickly cause another crack.

Good luck!
 
One pic looks exaggerated because the customer wanted a long-shaft height transom the whole width of the back of his boat, presumably for back-trolling etc... Another pic is my little model B. And the other was a step-down transom converted to long-shaft.

But, yes, replace your inside transom plywood. And get rid of that stupid piece of plywood on the outside of the boat. I hate that method. And replace with 1/8" to 3/16" aluminum plate, preferably bigger than the piece that was there. If you have a cheap source of aluminum, get enough to T it up over the whole back of the boat.

I like to replace existing transom caps with u-channel 1/8" wall thickness and 1" height. Speedymetals.com carries various sizes to allow for various thickness transoms. Be sure the inside dimension of the u-channel will accommodate both the thickness of plywood and whatever aluminum you place it over. Unfortunately, you do have to cut out some of the overall height of the u-channel where the motor will go, otherwise it clamps on over 2 different levels of aluminum. All of mine are held in place with solid 1/4" rivets.
 

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Unfortunately, you do have to cut out some of the overall height
of the u-channel where the motor will go, otherwise it clamps on over 2 different
levels of aluminum.

Ericman, wouldn't it make more sense to just use shims or spacers under
the motor mount instead of cutting the U-Chanel ??
seems like that is just defeating the purpose.



also, Please complete your profile when you have time as to what State you hail from.
 
Just look at the pictures dated 6-6-10. That's what I mean by cutting some of the overall height of the u-channel down. Just enough for the motor clamps to fit in there.

1/8" wall thick u-channel with 1" height works best, for me anyway, because it is strong and it gives you meat to attach with 1/4" solid rivets through the plywood, instead of just attaching with a wood screw through the top of the cap. The argument could be made that it could be or maybe should be tack-welded to the boat after the transom is put in. . . . but I do not weld, so that is why I do these this way.
 
Ictalurus said:
At a second look, it appears your transom is supported mostly from the outside, is that correct? Do you have a pic of the transom not so zoomed in?

Sorry it took awhile but here are a couple pics of the transom...

CB6955D2-9B51-4D53-9A6F-59768094EEE3_zpsgbmc4otp.jpg


https://i1298.photobucket.com/albums/ag58/jesse_long27/Mobile%20Uploads/7185DD85-9266-43D4-9B83-0D83C51367FD_zpszajfbxbo.jpg[/

[img]https://i1298.photobucket.com/albums/ag58/jesse_long27/Mobile%20Uploads/1FF5207F-9821-4B98-AA5C-F76684348D53_zpsavvyysku.jpg
 
The last 2 pics help a lot. I'd replace the exterior plywood, but try to fill in more of that recessed area, preferably attaching to more of that angled transom support near the bottom on the inside of your boat. Then I'd attach a plate of aluminum (1/8") that is the same exact shape of your new plywood on the outside. Then, no wood on the inside, but put a new cap over the existing like in my pictures. You want a "lip" above your motor clamps, just in case it loosens a little during transport, that lip will prevent your motor from coming off.

And actually, the way I would attach your new plywood would be to grind away the rivets that hold your transom support and use those holes as your guide and drill from the inside through your new transom board and bolt through those holes. All that should make it 2x stronger than factory original.

A note about a new transom cap. Make sure the inside dimension of your new u-channel is basically exactly the same as the outside dimension of your existing cap. You want a snug fit. Measure precisely and scribe it out so that when you put it in there, it will fit up tight to your corner plates. Then have someone put a good weld between your new cap and your corner plates. That should eliminate any future issues.
 
Looking at the overall pictures of the back of your boat, I'm guessing you are pretty significantly overpowered. I don't know if you can read the info on your manufacturer's tag, but looking at the width of the transom and the size and thickness of the plywood on it, I'd say you should probably be in the 8 hp range or less.

To use that 15 hp on that boat, you're going to have to make the new transom quite a bit larger to spread the load. I would go as wide as you feasibly can, and definitely make the new plywood go all the way to the bottom.

Your motor is pulling back on the top of the transom and because the wood is so narrow, it's causing major stress on the aluminum cap. If you simply fix the cracked aluminum, it's going to crack again in short order.

Can you give us the overall size of your boat WxL?
 
kenzy

Thanks for posting the second set of pics, they do help.

There are many ways to tackle this problem. For me, knowing my skills and resources, I'd replace the same system as what is there. Get some new ply, match thickness, and make a new exterior transom. If you can, go larger as mentioned for more support, you could go down to the bottom to put some pressure on the seam rather than in the middle of the transom. Just make sure you coat the exterior piece w/ 4 or 5 good solid coats of spar urethane. I've had sealed ply that is below the waterline w/ no problems after many years. Then, use some 1/2" ply and replace a section on the interior. Your motor clamps can dig into the ply for grip.

Now, I know others will say to do something else, like bring the wood to the inside, but for what it appears you're looking for and your rig, this should be an economical and relatively long-term fix.
 
kofkorn said:
Looking at the overall pictures of the back of your boat, I'm guessing you are pretty significantly overpowered. I don't know if you can read the info on your manufacturer's tag, but looking at the width of the transom and the size and thickness of the plywood on it, I'd say you should probably be in the 8 hp range or less.

To use that 15 hp on that boat, you're going to have to make the new transom quite a bit larger to spread the load. I would go as wide as you feasibly can, and definitely make the new plywood go all the way to the bottom.

Your motor is pulling back on the top of the transom and because the wood is so narrow, it's causing major stress on the aluminum cap. If you simply fix the cracked aluminum, it's going to crack again in short order.

Can you give us the overall size of your boat WxL?


max HP according to the tag is 15. It came with a 6hp Johnson but was just too under powered. The boat dimensions are 13.5' long X 48" wide.


Thanks all for the suggestions :)
Looks like some new wood and U channel are on order as soon as funds allow!!
 
Ok. Sounds good. I'd definitely maximize that new wood size and you should be good to go.

Before fixing any C channel cap over the top of the existing, make sure that your motor will fit over it properly and be able to clamp in place.

Good luck!
 
Well I finally got around to doing some fab work on my transom cap. I picked up a length of 1.75 x 1.75 x .125 wall U channel from my local Metal Supermarket here in Barrie. If you need ANY metal for any project, they're the guys to see! Great service and just good people to deal with =D>
Anyhow, on we go. I decided the best for now was to just re-cap the transom and go with a full overhaul in the off season (between ice fishing trips of course lol). I cut to length allowing for 2.5" of overlap on the corner braces to tie it in nice and strong. I had to notch each end with a hacksaw and cutting wheel, deburring all edges for a nice finish. After positioning where I wanted, I drilled through to accept 1/4-20 bolts. While test fitting I noticed, like mentioned in one of the replies, that I'd have to notch my cap to tighten the motor clamps. So off it came and back to the bench with the hacksaw and grinder. Once finished, it was a little pounding here and there and it went right back where it was..almost lol. I did have to go back with the cordless again and re-drill a couple holes but it worked out well! Here's a few pics of the test fit. I'll post up a couple more later of the bolted finished product when I get time. Thanks for all the advice and I'll try and be a regular around here to pay it back :D

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