When installing a motor mount on the transom, does it have to be mounted on the beam which goes across the bottom or can it me mounted thru fiberglass higher up. In my case on my cal25, that beam is not accessible.
Outboard mount on transom
- Thread starter josegatos
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You install the mount as the motor requires. Reinforce the transom on the inside where the mount will be located and you should be fine.
This is the part of the job that is called engineering, planning the place and the reinforcement. Installing these pieces is called work. In ordinary talk it is called figuring it out.
This is the part of the job that is called engineering, planning the place and the reinforcement. Installing these pieces is called work. In ordinary talk it is called figuring it out.
Mine is higher up. It also sits on a wedge that is thicker to the outside of the stern than the middle to compensate for the rounding of the transom. It is reinforced from the factory with a fiberglassed sheet of 1/2" marine plywood. I got the old ply out over the winter, laid in 4 layers of mat, resin soaked new 1/2" marine plywood, glassed it in and put an aluminum plate over the glassed in plywood to absorb any flex.
Yes it was mine. It is much more solid now than ever before. That picture was before the stern repair. I added a ladder while doing the stern work. I do not have a close up but it is very solid and the repair came out very good. After putting in 4 mats of fiberglass it was an easy glass job to fill in the place that got cracked. All fiberglass in the repair. This is the closest shot I have since putting her back in the water.
On our boat, the manufacturer glassed in a plywood plate on the port side of the transom for a motor mount, and this has been dependable. Recently I've added some aluminum backing plates, because the washers alone were sinking in a bit.
As you've already heard, you can add a backing plate of 1/2" marine plywood to help spread the load. In your shoes, I'd seek out other Cal25 owners to see what's worked for them.
As you've already heard, you can add a backing plate of 1/2" marine plywood to help spread the load. In your shoes, I'd seek out other Cal25 owners to see what's worked for them.
Remember the load on a transom-mounted outboard is PUSHING on the transom. I have seen too many installations where the owner or builder provided a really nice backing plate as though to keep the outboard bracket from falling off the boat, when in reality the REAL issue is to keep the outboard from pushing through the transom. They're not the same thing. In your 'engineering' phase be sure to allow for spreading the load over a wide area, ensuring a good bond between backing plates, and properly treating surfaces to avoid water intrusion and rot.
I have not done this yet but I aim to remove and replace Diana's motor mount using G10 backing plates OUTSIDE the transom, thus using the skin of the transom to spread the load. The plates are a little bigger than the aluminum ones of the mount itself and will get faired-in to look decent. The original 'plate' is 3/4" plywood inside the transom which is suspected to be riddled with rot. I will treat this with epoxy when it is dried-out and apply the backing plates as I reinstall the mount. That should be all right.
I have not done this yet but I aim to remove and replace Diana's motor mount using G10 backing plates OUTSIDE the transom, thus using the skin of the transom to spread the load. The plates are a little bigger than the aluminum ones of the mount itself and will get faired-in to look decent. The original 'plate' is 3/4" plywood inside the transom which is suspected to be riddled with rot. I will treat this with epoxy when it is dried-out and apply the backing plates as I reinstall the mount. That should be all right.
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