how to strengthen the transom

[Dave b]

I want to strengthen the transom for additional support for a 15hp 4 stroke outboard. It is mounted now but it flexes too much and I am afraid it willcrack the fiberglass. Thanks Dave B

 

[georich]

Strengthen the Transom

My O'Day 25 had the same situation with a flexing transom. Much of the plywood in the transom had softened and rotted from topsides leak. We tore out all the rotten wood, using a grinder and sander to get down to bare fiberglass. Then cut to fit some 1 inch salt treated plywood to fit into the space. The plywood was scored vertically every 2 inches so it could flex and conform to the conture of the transom. We painted both surfaces with resin and screwed them together until it cured. Next a couple layers of glass and resin, then sanded and painted with base coat. Lots of work but better than from the factory and ready to accept the new 15 hp.

 

[Droop]

Easy Way

Install a backing plate inside the boat on the transom. You can make it out of wood or this white thick plastic material. I think they call it King Starboard. You can use the motor mount screws to hold it on. The bigger the more support. Use large washers to distr the load.Good Luck!

 

[Dave B]

additional info on transom

I did use a Starboard backer plate but stillhave a need to make it stiffer. Would addingepoxy and glass matt help?? If so please giveinstruction..Thanks in advanceDave B

 

[Bruce Niederer]

A Stiffer Transom

Since adding the Starboard backer didn't give you the stiffness you need, you'll probably want to build a sandwich panel to get the stiffness you're looking for. This involves bonding a core (probably marine grade, untreated plywood - I'm not sure how epoxy would bond to Starboard) to the transom then laminating a couple layers of fiberglass to the plywood. In doing this, you don't want to just create this stiff transom independent of the rest of the hull, meaning, once the cored laminate is in place you should create fillets around the outside edges to bond it to the sides of the hull and tape over the fillets to spread the load into the hull.