1972 Hydrodyne mild restoration

Boat had twin 140's which appear to have pulled the transom apart. I am waiting for a 2nd opinion before I drop the $2000 for replacement. Next up is a full deck restoration (sand to bare glass, fair and awlgrip). Then a seat replacement. I could use some (used) outboard recommendations (make, model). Thinking of a Merc 115 tower of power.

 

That is a very nice looking boat, and welcome to the forum.

That wrap around transom plate places a stress concentration right where the transom failed, and is a bad idea. I have a similar plate on mine, but it is single engine, so there is not as much stress.

I need a little more information before I comment on the restoration. Does it have a flat raised floor? Is there an ID number stamped on the outside of the transom on the right side? If so, what is the number?

If there is a number there and the last two digits are 72, then the boat is worth restoring for sure.

Is the floor soft anywhere? Look at the seat mounting bolt area. Look at the rear of the floor.

I would try rubbing out the deck first. I have seen some pretty rough looking decks rub out.

Are you going twin or single engine?

Does the 2k transom replacement quote include removing the deck or cutting the deck?

If you are going single engine, I would go with a 90's or later V-6.

jim

 

Jim,
What is the proper shaft length? Using boat standards it would seem a 20" is right. Agree? Disagree?
Thanks for your time.

 

Agree, 20 inch.

 

I have a Dyne like yours that was used in shows with twins. The transom plate was used but it is failing further out where your is splitting. As a temporary fix, I inserted a 4x4 fence post sideways in the space in front of the well and dove 2 threaded rods from them, across the well through the transom and tightened a nut from the back until it supported the transom against the motor pull. Simple but not the prettiest but cheap fix for now. I will try to upload a picture.

 

Jim, My CMI number is CMA501500375. The digit after the CMA might be an S instead of a 5 ,I am not sure which. Why did you mention that if it was a 72 at the end it is worth restoring. Mine is a 75, What are the implications. Is that the manufacturing year ? I am thinking of restoring mine, that I have owned continuously since bought new.

 

That type of identification number began about the same time that they started using the end grain balsa core which your 75 has. The end grain cores rarely fail which makes the boat easier to restore because core replacement is rarely necessary.

The older boats with the core grain running length wise to the boat hull do fail and the restoration is time consuming and expensive. And there is a risk of not being able to keep the planing surface straight during the rebuild. A hook or rocker in the planing surface will destroy the performance.

jim

 

• Thank you ,Jim

 

wwmtn:

Looks like a good boat hull to rebuild if the core checks out, but you will definitely want to get that transome addressed correctly. $2K is around what I was quoted a couple years ago for my 1985 20 i/o but with the installation of new engine stringersfor the i/o, the price rose up a bit. I would have the transom done with the deck removed if this were my decision. would give the builder ou yourself a chance to properly address the top deck corners from inside. Good luck with your project and thanks for sharing,

Kevin-