fuel consumption

[reefman]

I'm 4 months into my new to me '02 2120 sc w/ 150 yamaha 2 srtroke. Thrilled with the boat and it has met or exceeded all my expectations. The only thing I wasn't prepared for was how much more fuel I burn than my previous boat (17' cc w 85 hp) I dont have a floscan meter so I can't easily monitor my usage. I typically cruise at 3800 rpm which pushes me along @ 18-20 mph. If I slowed down and cruised at say 15mph, could I expect to see a decent improvement in fuel economy?

 

[ryanc2]

Adding a fuel computer will pay for itself over a season. You can pick up a Northstar F210 for ~ $85 which will allow you to adjust speed in varying conditions to maximize efficiency.

 

[DaleH]

Yam performance bulletins, regardless of boat/hull tested, specific to the F150 motor, appear to show that THE best miles-per-gallon comes in at 4000 RPMs.

This assumes you are properly pitched. To do that, you need to know the maximum RPM for your motor, which Yamaha lists as 6K, according to their on-line specs. If it were my motor, I'd want my RPMs to be at least turning at 5700 with 1/3rd fuel and typical gear carried on board.

Oh, the MPG values were all above 2.0, most 2.5 to 2.7, but YOU are driving a heavy hull with a high wind drag full cabin on it ...

 

[DaleH]

He has a 2 stroke.

Haha! Well now ... THAT clearly changes everything!

OK, best RPMs should be between 3800 to 4200 I'd guess, and your MPG would drop to 1.8 - 2.2, depending highly on weight pushed and prop she wears.

 

[reefman]

I think i'd have to empty out a lot of non essential gear to hit 27+ @ 4000 but I'm in the neighborhood. I haven't run her @ WOT yet so I'm not sure what she can do but the Garmin unit she cane with shows max speed obtained was 37knts. Does that sound about right to people who run the 2120 sc?