Need support on building a transom on an aluminum sea king

Hello Yall.
I'm sorry I am very new to this site and also new to be having a outboard motor for my boat, I have always used a trolling motor. My 12' sea king that is light and can be carried by two people and also can be carried to the top of a vehicle to add a motor. I did see holes before I patched them on with screws and washers and a nut with 3m 5200 silicone to cover any leaks and now I just realized I need to make a transom since I bought a 15 hp outboard evinrude motor. I know you will say it's to much power but I am a careful driver to not even exceed full throttle for then the boat can be handle. I just want to make sure the materials and enough support to add the outboard on the back end of the boat. Please help me and God bless

 

Welcome to the forum.

Your boat should have a "capacity" plate or label on it. Don't exceed it's max HP recommendations for obvious reasons, but the less obvious one is the weight. A 15 HP 4 stroke, can be asking too much of the hull volume on some 12' boats, so check the label. If you don't have one, measure the transom from top corner to the opposite corner and post it here. A typical 15 HP outboard will need 1" of plywood (minimum) in the transom and this is best achieved with two layers of 1/2", glued together, especially if using construction grade, instead of marine plywood.

 

Photo of inside of the boat

I don't know the year but here is the inter design original. Before it was painted black. I don't even have the year when purchase from Craigslist but is register.

 

Thanks Par,
I will get back to you on the dimensions. The plate was not on when I purchased it. So still trying to find a rough estimate year of the boat. The 15 hp is a two stroke motor. It also feels like the weight of a 10hp.

 

Many 9.9hp and 15hp motors are based on the same design, so the weights are the same.

On some light 12' aluminum boats even a 9.9 can be a little too much, so if you use a 15 on there be careful.

The boat should have had plywood attached to the transom when new so an outboard could be mounted, I don't see any on the inside in that pic, could be on the outside though. There may be an outline of where the wood was first mounted, if not make the plywood cover as much area as possible.

Some of these old boats were made to be very light, so when used with an outboard over time they tended to develop cracks in the aluminum on and around the transom.

 

Ondarvr,

Thank you with some notes with the outboard. The outside there is no wood but there is wood inside that is 1"x3". Ill send more pictures later right now the boat at my neighbors up in the hills. I will be camping may 16 and would like to get this motor on the boat before the time comes. Since this year coming very fast .