Fuel efficiency in Power V 115 two stroke

[kevin donald]

I recently purchased a 19' Arima Hardtop. I am only getting 1 mpg with a Yamaha Power V 115 two stroke. I have been running the engine on small chop in the Columbia River, 3500 - 4000 RPM at 24 mph. Only 1 person in the boat. Any advice?
Thanks!
Kevin

[boats.net]

You might try a smaller pitch prop if can, operating range is 4500-5500 rpm's and rev limiter activates at about 6200 rpm's, prop to high end of range for better fuel economy.

[kevin donald]

Fuel efficiency Power V two stroke

I am so new to this I don't know where to start. Aluminum or Stainless?
What size and pitch prop would allow me the best mileage?
Thanks!
Kevin

[boats.net]

What prop do you have now and what rpm's are getting at wide open throttle?

[LLAMAHA]

I have an '87 V4 115 that performs like a big block Johnson 140. My boat is a Crestliner 18 ft deep V and very heavy with all the lead and toys. It will do about 3 ~ 4 mpg at max range cruise which is 3400 ~ 3600 rpm and 30 mph. This happens because the engine mounting is at the optimal trim height and I'm using a 21 inch stainless performance prop which will turn 5800 ~ 6000 rpm on a good day. I have a fuel-flow monitoring system that confirms the efficiency values. One thing is evident: engine rpm and fuel flow are almost perfectly linear, meaning that more rpms equals more gph. At 3600 rpm my rig burns about 8.5 ~ 8.7 gph and the speed is 30 mph. Speed numbers are GPS confirmed, also.

My suggestion for you is to experiment with different props. Will your engine reach 6000 rpm at full throttle? It is limited to 6200 by the gov. A so-called double cupped stainless performance prop might be a worthy investment as it has been for me. My original Yamaha prop was worthless and unstable on my boat at 19 inch pitch and maxed out rpms. You may want to try more pitch as long as your engine can still reach its 4500 ~ 5500 rpm range.

[99yam40]

Do you realize you just gave 2 different GPH fuel burn rates for the same RPM and MPH

[kevin donald]

fuel efficiency on Yamaha Power V 115 two stroke

I tested the RPM rate yesterday. At WOT I the engine will only reach 5200 rpm. top speed is around 30-32 mph. The engine appears to be mounted correctly. Unfortunately there are no numbers to be found anywhere on the two identical aluminum props.

Ideas?

Many thanks!
Kevin