Last time I looked at a SUBARU vehicle the drive train was using a constant-velocity transmission that had rubber belts. While I think the car is a nice design, the rubber belts in the transmission were enough for me to drop it from consideration to purchase. For that reason, I would be very cautious using a SUBARU with a constant-velocity transmission as a towing vehicle.
The total towing weight limit of 1,500-lbs and a tongue weight limit of 200-lbs are in harmony. As a general rule the tongue weight should be about 10-percent of the total trailer weight.
The hull weights for the 13-foot and 15-foot hulls are listed in their REFERENCE section pages. See
http://continuouswave.com/whaler/reference/13/and
http://continuouswave.com/whaler/reference/15/for information about the bare hull weights.
The weight of modern outboard engines is available from their manufacturers. The weight of older outboard engines is available in a comprehensive archive thread at
WEIGHT OF OLDER OUTBOARD ENGINES
http://continuouswave.com/ubb/Forum3/HTML/011042.htmlThe weight of a trailer will vary with its construction. To save trailer weight look for an aluminum trailer. Trailer weights are usually listed on the trailer itself on its capacity plate.
When buying older Boston Whaler boats there is always a concern about the hull having gained weight due to retained water entrapped in the double-bottom sealed hull construction. For that reason, you should figure that the published original hull weights are going to be lighter than any actual hull you might own.
Vehicle towing weight specifications are generally given for the optimum vehicle configuration, usually allowing for only the driver to be in the vehicle and for the driver to weigh about 175-lbs. The weight of anything else in the vehicle, including any other passengers in the vehicle, will need to subtracted from the specified maximum rated towing weight .
Towing at the maximum rated towing weight is never the best option. Acceleration, handling, and most important braking will all be more difficult. That said, I am sure it will be possible to get under the 1,500-lbs with careful selection of boat, engine, and trailer.
By the way, I towed a 15-footer around the Great Lakes for several years. I used a Ford V8 sedan with a 5,000-lbs tow rating. I added an auxiliary transmission cooler to the engine before I used it for towing.