wood transom for poontoon

[hondapapa]

I have a 1995 Manitou pontoon 24 ft with a 1995 90 hp force motor. Wood has got to be replaced before splashing this year.I do not want to use wood.I have some 1 1/2 inch aluminum plate,but I was told not to use it because it will not flex. Somebody said to use plastic instead. What do yall think?

 

[1983 ercoa 21']

Nothing wrong with wood if done properly.
Most of the newer toons are all aluminum.

 

[ahicks]

I think if I had the alum. and a way to cut it to size, that's the way I'd do it.

 

[hondapapa]

Thanks guys that's why I wanted to use aluminum, I can make myself. Just concerned about welds cracking in thin alu its bolted to. some one said it would.

 

[ondarvr]

Are you saying you have 1.5" thick aluminum plate, or one .5" thick plate? It's just that you don't see that kicking around that often.

A pic of what you're talking about would help.

 

[Scott Danforth]

Welding heavy plate to thin plate requires a special transition to not produce a stress riser and cracks. I myself would do two 3/8 plates sandwiched over 1-1/4" tube structure to get a 2" transom much lighter than a 1-1/2" thigh hunk of aluminum

 

[ahicks]

Thanks guys that's why I wanted to use aluminum, I can make myself. Just concerned about welds cracking in thin alu its bolted to. some one said it would.

Your current ply mount bolts to heavy galvanized or heavy alum angle, correct? I would doubt there would be any issue with that cracking - unless you plan on exceeding the HP rating for that mount.

Agree on the solid construction vs. built up. The only part of that mount that really needs to be 2" is the upper part of it, like where the upper bolts go through. The bottom part could be from thinner material, like 3/8" or so. There's a few ways to go there.

If this is a concern over harmonics, I wouldn't let that bother me too much. The engine vibration is pretty well isolated from the rest of the boat with the internal rubber motor mounts. What goes on with the part(s) that bolt to the transom won't make much difference.

 

[Water logged]

Is the wood currently bolted to the engine pod ( doubt it's welded)? Can't the aluminum be cut to shape, drilled, and bolted the same as the wood is now. You could sandwich some .5 inch plywood to bring it up to 2" if needed. The plywood could also separate Aluminum from galvanized steel if that is present. PLASTIC????

Glenn

 

[hondapapa]

Ok changed my mind. Are men allowed to do that ? I built it out of marine ply wood. Question now is Would covering it fiberglass make it last longer or it worth the trouble ? Nothing is better than working on your boat with some cold beer except using it.

 

[mpilot]

You could just epoxy it and that would be better than just raw boards. If you are going to glass or epoxy it and the boards are sandwiched you might want to consider putting the same epoxy inside. If you do the above though make sure to seal the holes it bolts to the aluminum and use silicone to seal the motor mount holes.

 

[ahicks]

My experience has been that the better you seal wood, the better it is at holding moisture IN.

 

[oldboat1]

To seal, consider WOG's sealant of 1 qt linseed oil, 2 qts. mineral spirits, and 1 qt. spar varnish.

I have some extra pieces of laminated joists that I've been using for motor mounts. Stuff is really heavy duty, as one would expect -- to my eye, similar to marine plywood, but thick. Very dense, no voids -- stuff I have is approx. 2 inches thick. If you can locate a piece of that at your lumber yard, might be worth a look. Mine was left over from construction of my garage -- not sure what you would run into if trying to buy a section of the stuff.

But I've used the usual double layer 3/4 ply many times, and never a problem -- construction grade for this is fine. Do not use treated ply. I recommend epoxy or 5200 to bond, along with drywall screws. Seal the whole piece with epoxy or WOG's brew, with special attention to the edges. For a two inch thickness, sandwich in a piece of half inch ply.

 

[River Rover]

Ok changed my mind. Are men allowed to do that ? I built it out of marine ply wood. Question now is Would covering it fiberglass make it last longer or it worth the trouble ? Nothing is better than working on your boat with some cold beer except using it.

lol- You and I would get along just fine....I could be wrong but I believe i'd leave the marine grade wood as is- if you seal it moisture would still get to the wood and take much longer to dry- that's a biggie on wood- it gets wet....the quicker it air dries the better.....