Using my boat as a trailer

Now I'm getting closer to what i'M TRYING TO DO. The center point in the boat is at 8'.
2/3rds of the weight is aft of center. this is where water and fuel tanks are plus say a 25 hp 4 stroke engine. Forward of center is open area plus anchor and rope storage at the bow. I can set the axle at 6' or 7' or at 8' and with blocking stiffen the 2x6 bottom frames
which will all be tied together as one with a double to support the axle all epoxied and bolted together with 3/8 galv. bolts. Boat is 6' wide at the bottom 16' long. Where should you set the axle? The front 8' is a shallow V-- 3/12 pitch and should lift clear of the water under power. the aft 8' is flat bottom.

 

As you would already know the draw bar needs to have a fair bit of weight on the toe bar, but also allow light enough to manually lift on to a jokey wheel.
If you motor and other weight at the back then your axles should be in the flat bottom area.
Any other information I would need a rough drawing to see what you are thinking.
A down fall is you are I presume, building in wood
The design boat you have is perfect for aluminium design with a light torsions suspension such as you suggest rotational and the wheels could be small aeroplane wheels that can take extra weight.
If I had the titanium suspension in production it would of made every thing simple because of the weight is about 3 times lighter that the 750kg steel torsions, plus they do not rust and give an upmarket affect.

 

This is the 12.m trailer barge that had 3 set of 2000kg torsions altogether 6000 KG.
I gave the customer the quote price, he said yea that's for the aluminium, but how much is it to build the barge, I replied that is the price to build as well as I still made profit but never charge extra for what the Aluminium cost me.
When finished manufacturing this trailer barge he placed a 115 Johnson out board and easily did 30 knots.
He phoned expressing his amassment on the performance and gratitude which makes it all worth while.
Each day he would tow the barge straight into the packaging shed with loads of mussels and then load equipment on deck and head back into the harbour.

 

This is another version of plug in wheels that work well on uneven ground although not as good towing as the rubber cord torsions.
I have actually crossed this design with the titanium torsions for the outback's in Australia such as torsions rubbers cords ware quickly and not used, so I have designed an independent suspension as pictured and placed on the end of the titanium torsion axle, for less strain on the rubber cords, also far more stable on uneven terrain such as large potholes.