TOPIC: Tramsom inspection for internal rot.

What is the best way to discover if a transom is solid. The Larson Thunderhawk Jr. design gives the transom much more reinforcement than a standard boat design so stress cracking is less likely. How can I find out if I have a fiberglass sandwich with a fluffy dry rot core?

Obviously I could drill a hole, but that would only tell me what the material is like where I drill. Tapping and listening doesn't really yield any good data. A big C clamp can only check the top edge.

Thanks.

Good question. The best way I have found to check the strength of a transom is to lock the motor in a tilted position, then yank downward on the lower unit violently, like you are trying to break the tilt lock. Don't get carried away with this though! If it is a vintage Evinrude or Johnson with a little pin that locks the motor in the up position. don't do this, as you can break the lock. Best to lower the engine on these and stomp your foot against the rear of the exhaust tower at the base. The idea is to stress the center point of the transom to see if it " gives" or bends at all. You may need 2 people to do this, one to reef on the engine, while one looks across the transom to view any sign of movement. Some boats are so rotted that this will make the transom flex outward like rubber. It may not sound like a elegant approach, but it is simple & will give you a good idea of the condition. Keep in mind, that a rotted transom that has not seen use in many years, may appear solid, only to quickly turn to "mush " after a few outings. Bad transoms area fact of life in the old boat hobby.

The design of these old Larson Falls Flyers and Jr. Thunderhawks does not allow for an aluminum plate or anything like that to disburse the pressure from the motor thrust either. On a typical flat transom, another layer of some strong material can "fix" the problem for a while, or just buy you a few seasons of time.

step up on the cavitation (ventilation) plate and hop on it a few times. if the transom doesn't move your good to go. ron

The problem here is that the transom is only around 14-16" wide. Moving or bouncing the engine up and down doesn't really have much effect on whether the transom will give any "bounce". It's really rigid with the bracing that it gets from the rear deck that wraps around the engine. Even if the wood was water-logged or powder, the transom would still pass these tests. I think that the only way would be to drill into it from the top. That way if the wood was good, you could just fill the holes with epoxy and re-gel the top. If the wood was bad, you could cut the top off of it and replace the wood from the top and then re-glass and re-gel the top of the transom. It's such a small area to work in. I hate to drill into anything if I don't have to.

Lee Wangstad

i jumped on a few when looking for our project x boat a few years ago and believe me, they moved. i was told by a marina owner this was the way to do it, if you didn't want to start drilling holes.

Lee,

I assume the 1-1/4" thick transom wood goes all the way across the boat. Not just where the motor mounts. Correct?

So replacing a transom would involve removing the interior fiberglass and pulling whatever is there out through the back seat.

I'll bet one of those new sonic-crafter vibrating cutting tools would work great! It might even make the job, dare I say....easy.

The important thing is to wait for the hottest day of summer and work in a hot garage when sanding fiberglass.

It doesn't go all the way across the back, it's focused just at the center part between the rear deck extensions. The deck extensions are an integral part of the structure at the rear of the boat. You could split the deck from the hull, but they are put together without any thought of anyone ever wanting to go back to split them apart again. I've never seen a bad transom on a Thunderhawk. I'm sure that they're out there, but I haven't come across one yet. You might just have to go by the "thunk" test and run with it.

Lee Wangstad

That's quite a testimonial to the design and construction of those boats coming from you, Lee. Your Thunderhawk has to be in my "Top 5" list of all time great restored 'Glassics, it's absolutely stunning.

Sorry for the intrusion, Jepster, I couldn't help myself. This knowledge should make you feel great about your project though, have you got any pics you can share with us?

The photos need to be taken lightly.
I bought the boat in Iowa. I asked the fellow if the trailer could make it back to MN. "Sure we drove 85 miles on the freeway with it last week" So.....when I got here, I could wiggle one wheel almost and inch of wobble, the bearings were so bad. In haste, at 4:00 pm in De Moines, I'm running all over town trying to find a new hub. These situations always restore my faith in human life. People were helpful and I got what I needed.......on the far side of town.

The important thing to note is that the owner could not tell good bearing one from a wildly dangerous one.

Ysterday I removed the 3" black paste on letters proclaiming "HUMDINGER II" As a joke, until I get to the external restoration it now says "DINGE"

I sold the 1970's Johnson 40 to a buddy of mine who had a Chrysler that was on the fritz and needed some expensive parts to fix. He discovered they had been in the Carburetor and installed the wrong float which worked badly, but well enough to cause massive frustration.

I have a 1960 Evinrude Lark 40 with a 59 shroud that I just put on it last week. I still need to get it running. It has been lying around my shop for 15 to 20 years.

The boat is a mess. Full of pop cans, stale sun tan oil bottles, and leaves. The windshield was made from a piece of 1/8" Lexan rather than 1/4, but then someone used a chemical in it that made it translucent rather than transparent. The surface has stress cracks in the gelcoat and there are some scratches and a few other cracks in the structure here and there, but still much better than where I started with my 57 Falls Flyer! The Flyer had trees growing in it. I'm missing the plexi tail fin stern lights but I think some one makes them...(Lee, hint hint).The hardware is all there, and if I can get the motor to run I'm going to test it out yet this year. In spite of the nasty appearance, I think it is sea worthy.

I put forth this disclaimer..." This is not the world's crappiest boat....It is a restoration project."
[img] [img]http://www.fiberglassics.com/media/kunena/attachments/legacy/images/Dinge.jpg

The transom may be sound, but I think this reinforcement rib needs replacing. Maybe I can get another year out of it. What do you all think. LOL

You may end up going to the extreme like I did, but it worked.

Nidabond... pourable transom material...

I did my '67 MFG with it... and if i had it to do over again- would have done the Fabuglas as well..
REALLY tough stuff!! and you never have to worry about it again.
I will most likely do the Hydra-sport with it too... before selling it.

I used Seacast, but they must be similar. It was work, but now I could use the boat in a James Bond movie, as the transom is bulletproof.

Yes, Seacast and NidaBond are the same basic stuff. The Nidabond was less expensive for me when shipping was included.
I agree- Bulletproof!