adding a aluminum transom on rebuild

[bdva]

i recently bought a older 20ft pontoon, i am making it into a duckblind/fishing/booze cruiser, the motor that came with the boat(1964 merc 35hp 350 twin) was mounted on a angle iron homemade transom, i have redone everything on boat including painting pontoons, i want to add a Aluminum transom that i picked up, My question is...How far back from the last cross brace/ back of the boat does the motor have to be? see pics, thanks for the HELP, Brian

 

[ahicks]

With the engine installed, tip it all the way up. You'll see the top front of the engine's shroud swings forward quite a way. The taller the engine, the further forward it's going to swing (thinking old 6cyl. Merc. here). If you can clear the engine when it's all the way up, thinking you're golden!

Myself, I would want a wall in front of the engine to help control the noise when under way. So you might want to consider that as well?

With the transom assembly you have, it might be a good idea to double up on the 2 rear cross members?

 

[deadend]

I just went out and measure on my 18' and the back side of the transom is 17". It is 12" from back of transom to the cap weld on the toons. As ahicks pointed out I would double that rear cross member. I just redone my pontoon and my work toon at the lake not having extra cross members I got a piece of 3 x 1 1/2 x 1/4 alum channel and bolted to the rear crossmember.

 

[bdva]

thanks for the info, yes i do plan on adding to help strengthen, i will look into building something to help keep noise in check, thank you both for responding