Transom repair

[Kentfielddude]

Hi I have a 11ft hydroplane runabout and I need to raise/repair the transom. I have made a replacement piece of wood by glueing marine plywood on either side of a piece of mahogany. How do you suggest I best secure the wood. I was thinking of putting vertical metal rods or dowl rods through the transom and into the new piece of wood. And expoxying and fiberglass the wood and then putting aluminum plate over transom.

[deverhart1]

I use an aluminum angle inside and a flat 2in wide on back with 3/8 bolts thru top and bottom. I am able to have different transom heights this way for different antique classes by using different heights of insert boards. I used multiple pieces of okuume plywood to proper thickness laminated with West System. The bottom bolts are eye bolts for rope motor tie down. If you don't understand give me your email addy and I'll send pictures
David Everhart S52

[DeanFHobart]

Hi I have a 11ft hydroplane runabout and I need to raise/repair the transom. I have made a replacement piece of wood by glueing marine plywood on either side of a piece of mahogany. How do you suggest I best secure the wood. I was thinking of putting vertical metal rods or dowl rods through the transom and into the new piece of wood. And expoxying and fiberglass the wood and then putting aluminum plate over transom.

Per the above response... Do you need various heights?

[Kentfielddude]

No I dont

[johnsonm50]

In that case assuming you'll want a fixed transom, 1st since the motor's stress pulls backwards away from the top of the transom - I would advise putting a bevel in the vertical cuts wider towards the bow. Then match that with the transom piece. If its already made to fit it can still work but I like to use physical barriers when possible so not to rely on just glue or fasteners. That said if you make & epoxy in the transom, sandwiching it in aluminum will also work.
The idea above from David is something to think about, the set up on the boat now was for a motor height you might want in the future so not permanently gluing in the wood filler piece is reasonable in that a well made aluminum sandwich is going to be strong enough leaving you the option to change. If you haven't driven this yet with your intended motor, you won't know how it reacts till you do. You could end up wanting to change it for a host of reasons. Good luck, Have Fun.

[ZUL8TR]

What engine are you planning for the boat?
Is it a racing gear case and tower or a plain service engine?
Regardless the correct height to run is a trial process in a race hull and you need vertical up or down to get it right for the purpose you have in mind. Therefore if fixed you need to get the insert transom height right to allow for shim sticks to adjust height for different props and other. If transom insert too low too many shims may be required to go higher and run out of engine clamp area, if insert too high need to cut transom insert.

What is the present thickness of the transom? Remember if you go with aluminum sandwich to a wood block depending on thickness of alum used for strength it could wind up too thick for the engine clamps to fit over.

Reconsider adjustable insert for getting height close to right for shims and for different future engines as deverhart1 suggests.

[johnsonm50]

What engine are you planning for the boat?
Is it a racing gear case and tower or a plain service engine?
Regardless the correct height to run is a trial process in a race hull and you need vertical up or down to get it right for the purpose you have in mind. Therefore if fixed you need to get the insert transom height right to allow for shim sticks to adjust height for different props and other. If transom insert too low too many shims may be required to go higher and run out of engine clamp area, if insert too high need to cut transom insert.

What is the present thickness of the transom? Remember if you go with aluminum sandwich to a wood block depending on thickness of alum used for strength it could wind up too thick for the engine clamps to fit over.

Reconsider adjustable insert for getting height close to right for shims and for different future engines as deverhart1 suggests.

The thickness is a good point, I've used 3/16 inside & 1/8 out, it's worked well. 1/4 inside if more than 35hp is used is adviseable

[Jakeroub]

I've done something similar in the past. I used a router to cut a groove on all three sides of the newly exposed wood (very easy to do), with width something like 1/3 the thickness of the transom. The groove might be 3/8" or so deep. Then made the new piece with a corresponding tongue that fit into the groove, and epoxy in place. SS plates on both sides. I don't believe the plates I used were particularly thick or well attached. With a tongue and groove arrangement, there is little chance of your new piece escaping.