Glen-L.com

Was Talking with my uncle who used to run a lot of flat bottom type river boats with outboards. He said that often if they over powered the old woodies they would tear the transom off the boat. What I am wondering is why? Over torque from the outboard with a jet? Weight? Trailering? Rot? What are the major concerns with assessing motor weight vs boat size and torque also what modifications can be made to transom designs to strengthen them to prevent this tearing. (im building a 16 ft scrambler btw and am thinking of puttin g a new 75hp etec with a jet on it)

Add some extra transom knees midway between the knee and the chines, Make sure your motor well is sturdy and tied into the frames, and always transport with a transom saver motor support will help.

Roberta

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Roberta
Built Zip "Oliver IV" and Super Spartan "Jimmy 70"

I would do every thing that Roberta has in the posting.

The reason transoms get torn off is too large a motor for the transom, boat pounding in heavy waves, rot, trailering with motor bouncing, and loose transom clamps are just a few that I can think of.

Yep, I agree with what is said above (strong motorwell side supports, knees, transom saver). I have no experience (yet) with a broken transom. I do have a 16ft Glen-L boat with a 2007 ETEC 90 bolted to the transom. That engine weighs 320lbs just like the 75 you mentioned. I have an oversized center knee with a strong back extending forward to the frame. I added two really large 2" thick knees that extend all the way to the top of the transom on each side of the well. They also extend forward to the frame. Those are epoxied and fiberglassed with biaxial glass. They are also bolted through the transom and the bottom and the bolt holes are sealed with 3M 5200. I use a really good transom saver between the engine and the trailer so that the trailer takes the weight of the engine when I hit a bump.

There was a thread last year about a guy with a zip that had a large engine and no transom knee. He trailered it from somewhere in the midwest to Florida without a transom saver and broke his transom. At the same time that thread started, I was realizing that my big engine was probably a transom killer and thanks to some patient people here, I was able to build and add some new support.

There is another guy here in the Atlanta area who had to rebuild his entire transom. Maybe he'll see this and add some thoughts.

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2011 MALAHINI - KICKED IN THE HEAD

I wake up with a 16ft woody every morning
Video: http://www.youtube.com/watch?v=534DBtp1Cnc
Website: https://sites.google.com/site/2011malahini/

The Scrambler is rated to 100 HP. Just follow the design instructions for the transom and you will be fine. If you cut corners then you get in trouble. Just a word of caution for anyone. No matter how strong you think you've built it, if you run an open throttle for too long in a heavy chop you could be asking for trouble. Common sense in operation is just as important as following the building plan, maybe more.

One consideration as to the size of the motor to be used is the weight of it. My old 50 hp Merc weighs only 165 lbs. A new 50 hp Merc weigh about 100 lbs more. The new 100 hp motors are HUGE compared to the older 60s ad 70s vintage motors.

Roberta

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Roberta
Built Zip "Oliver IV" and Super Spartan "Jimmy 70"