Thomas --
To answer your question -- if the manufacturer took a 90 HP, and tuned it up to achieve 115 HP, for example, it would be the same (small) displacement engine, and they would most probably have to increase engine RPM's to achieve greater horsepower. In other words, the engine would have to work a lot harder to achieve the desired level of horsepower. The whole point with Honda detuning a 150 HP engine block is to make a low-rpm, high-displacement and high-torque engine that essentially blows away its competitors in economy and smooth operation. Actually, we got around 5 statute miles per gallon on our Marinaut, but that is still phenomenal. On the Marinaut 215, the transom easily took the added weight of the Honda BF115 and Tohatsu 9.8 HP electric start, long shaft kicker without adversely affecting trim.
As for getting the Marinaut out of the hole to go on plane, the high-torque BF115 causes the boat to leap out of the hole. I don't think the BF150 would do any better at getting us out of the hole. The top-end RPM's of a BF150 would allow the boat to travel faster, but for what constructive purpose? My wife and I took the Marinaut to 31 Knots, and we did not feel comfortable at that speed. We prefer around 19 to 21 Knots, because this gives us an excellent balance between stability, safety, speed and fuel economy.
Finally, the Honda BF115 is an engineering marvel. I think that Honda may be losing ground in this bad economy not because of its technology, but because their engines cost a little bit more to manufacture. I learned my lesson year's ago on pinching pennies with a decision between buying a new 1994 Ford Taurus or a Honda Accord. I chose the former, because it was $1,500 cheaper than a Honda. Big mistake -- it was cheaper. My superbly maintained Ford lasted 9 year's before it had to be scrapped due to a bad transmission. The transmission could have been fixed for two or three thousand dollars, but the car had too low of a book value to make it worthwhile. On the other hand, my mother had a 1991 Honda Accord, sold it 13 year's later for $3,000, and it's probably still running today. We get what we pay for. Honda's engineers are brilliant, and they make proven, technologically superior products that stand the tests of time.
Thanks,
Rich