Advice on outboard motor wedges

g,day,
I have built a 6.2 meter aluminiumn plate boat, 5mm keel sheets, 4mm sides, powered by a 140 suzuki. The transom angle by the plans is 13 degrees, When I first trialled the boat and had the engine fully trimed in it is right on the edge of porposing, as I could not trimm the bow down enough. I fitted a set of three degree motor wedges and the boat works well in the rough now, but my problem is that this has made my transom an inch thicker at the top and the steering cylinder fowls it when I tilt the motor for transport. i would like to rectify the problem properly but can only think of two ways to do it,
1, cut the back out of the boat and rebuild the transom to 16 degrees,
2, Remove the wedges and fit trim tabs to the boat

Would the trim tabs work? as there is a fair amount of work in redoing the transom? any veiws appreciated, troy

 

Pictures Troy. Lots of pictures. The description of the problem is a bit of a puzzle. Can't guess at a solution without seeing the boat.

 

I don't see why trim tabs would not work as you wish. A simpler solution might be to add some wedges under the transom. You can experiment with some wedges cut from wood and taped to both sides of the bottom at the transom. This will cost nothing and allow you to find out how much wedge is needed. I've done it with wedges cut from a 2x6 with varying height of the wedge at the transom. Start with about 6" width and height of 1/2" and go up or down as needed. Of course wedges don't allow adjustment like trim tabs but the motor tilt can be used to trim the boat out.

 

You could move the engine out from the transom on a small pod...this would allow you to change the angle....see pods on www.stabicraft.com but these project rearwards 18 in while you only maybe need 4 -6 in This is the one on my 6m stabicraft....easier to weld a thinner version of this on than to tear the back out ....also means you can lift the motor a little which is better for shallow water ...zoom in on the right hand picture ...does not go all the way down the the bottom of the transom though you can if you want ....

Had another thought .....cut the transom vertically on two lines 18 in apart ...bend centre back to correct angle then weld in two vertical wedges and re make top of transom ...design feature ....

did you try some fins on the leg these tend to push the back up fast when going onto the plane and will in effect be adjustable trim tabs as you move the motor...

 

Hi Troy

I have had a couple different variations of this problem.

One boat had no dramas with trim related porposing but when the motor was trimmed all the way up the hydrive cylinder fouled on the transom. Soloution, there was -no solution, the motor trimmed up enough for a travel leg to mount, and also went high enough for the leg to clear the bottom of the boat. So we accepted the loss of trim and the boat went out, the customer was made fully aware of the problem.

Second boat had insifficient negitive trim so a set of wedges were installed, fixed the problem but then the cable steering fouled on the transom cut out. We had to scollup the transom so the steering would not foul.

I know it's not really a definitive answer for you, what sort of steering do you run? I noticed recently that a customer had installed Baystar "bullhorn" set up, this is a similar type of set up as the hydrive but dosn't seem to foul on the transom motor mount as the hydrive dose. Changing the steering to a different type would be alot cheaper.

Cheers