Re: Tounge Weight
Basically, here's how it works. The amount of torque exerted by the tail end of the load should be roughly 90% of the torque exerted by the front of the load. Let's say you have a load that weighs 200 pounds and is evenly distributed along the length of a 20 foot trailer (ridiculous, I know). If you put the axle half-way along the trailer at the 10 foot mark, the axle would essentially balance the entire load and there would be no tongue weight at all. This trailer would dolphin on you up and down the road, very dangerous.
Now let's say you moved that axle to 8 feet from the rear of the trailer. Now you have 8 feet behind the axle and 12 feet in front of it. Using some fancy math, you figure the torque on the back half (trying to raise the tonque and drop the back) is -320ft-lbs. The amount of torque up front (trying to drop the tonque and raise the back) is 720ft-lbs. The trailer would be very tonque heavy, perhaps too much for your tow vehicle.
A more ideal measurement would be 9 feet from aft, giving you torque numbers of -365ft-lbs and 605ft-lbs, which would be somewhat reasonable. Of course, these numbers assume that the load is evenly distributed. In practice, this is impossible with a boat.
In your case, the heavy outboard and light body is going to place much more torque on the rear of the boat than on the fore, so you'll have to move your axle back further. How much I can't say without some numbers. How much does your boat roughly weigh, how long is your trailer (including any portion of the boat that hangs off the back) and how heavy is your outboard? With that info, we can get pretty darn close.
