2001 Honda 115HP, needs different prop.

[staticman4414]

I have a 2001 Honda 115HP Four Stroke on a Lowe FM169 Aluminum fishing boat. We use it more like a fish and ski however. We just bought the boat and motor combo and is currently has a Stiletto SS 3 blade 13.25" by 19 Pitch prop. With my wife and I sitting in the middle seats of the boat (600lbs people and gear), and full tank of gas, I was a bit disappointed with the nose up take off of the boat and slowness to plane. This was with the motor trimmed all the way down. Once up on plane, the boat seem to perform decent, with a top speed of 43MPH by GPS and Engine RPM at 4900. The boat also seem to really bounce a lot in the water. Maybe this is just part of this boat, but it is worse than any boat I have ever been in. I need to keep the engine trimmed way down most of the time to keep it from being such a misserable ride that we are ready to head in as soon as we get out there. This is in reasonably smooth early morning water on the Ohio river even.

So it appear my motor produces max HP at 5500rpm and redline at 6000, yet I am only getting to a WOT of 4900rpm. So I assume my boat has too much pitch on the prop. Honda's prop calculator says 13.25 or 13.875 by 17pitch - 3blade. From all my reading, I am reading that I will gain about 200rpm per inch of pitch drop. So if I went to a 17pitch, I would estimate I would be at 5300 rpm which is still not even to max HP rating. This is my first Four Stroke Engine, so I don't know what to expect compared to the merc 1980s tower of power units I have had in the past. I had the same size and pitch prop on a 17' bass boat with a 1981 90HP merc and it did very well. So should i go all the way down to a 15 pitch? The engine seem to run very well and seem have no problems, but it is new to me, so I am not sure of that. I also see where holes are drilled for a stingray fin on the outboard, but it doesn't have on it currently. Thanks for any advice. We will cruise more than anything with this boat and pull a tube or knee board from time to time.

 

[Sea Rider]

Sometimes crazy boaters like putting props on wild guesses assuming that will work spot on for their combos. Ideal is to test factory deliverd OEM props as currently loaded and then go for a prop maximization depending if needing more or less wot revs.

If combo has deck weight evenly balanced you need to sit OB at 90? for when at plane boat and cav plate rides parallel to water level. Seems will need to invest some money dialing a perfect prop for that combo. I would start by testing a prop recommended by Honda prop calculator, check max wot rpm achieved as currently loaded and go from there for another less pitch if revs are still tad low, or even modfiying Honda prop pitch at a prop shop.

The Rule of Thumbs of + 200 vot revs per one less pitch does not always dials that, conservatively would go per one less pitch instead than 2 if yours is a light or medium light combo.

Happy Boating