And saved 5-6 lbs... for a 3.5 HP 4 stroke. I have since decided that greater horsepower and a detached gas tank would have been worth the 5-6 lbs. The range of the detached gas tank, plus the ease of not having to fill up en-route would have made all the difference.

An engine in the 5 HP range with external tank would all me to plane when desired, give far longer range, and still not weigh more than about 55 lbs.