yamaha ox66 250 fuel consumption

hi, i have twinn 250 yami ox66 on my grady white marlin, i average about a mile per gallon according to my fuel management sytem this seems horrible 2 me, any ideas or is ths the norm? ( cruising speed approx 28 mph)

Re: yamaha ox66 250 fuel consumption

You are in the ballpark as far as mileage goes. I had a 28' proline walkaround with twin 250 vx76s on it. Mine are basically carbed versions of the OX-66. My mileage averaged about 1mpg also. I have talked to numerous people that ran both engines, including several well respected LA dealers. Everyone told me the same thing. 1MPG average unless it was a very very light boat. You may try a good full tune up, and playing with different props, and weights, etc, but its not gonna change by much. They are very strong engines, but very thirsty. I ended up putting twin DF250 suzukis on mine and doubled my mileage across the board.

Re: yamaha ox66 250 fuel consumption

I found this older performance bulletin on Pursuit boats website.

http://www.pursuitboats.com/Archive/offshore/pdf/3070cc/3070_OFF_CC_250EFI2.pdf

Grady Customer support may be able to provide you a report for your model.

Are both engines reporting the same gph in the fuel management system?
I had an issue where my stbd was burning 10gph while my port would sometimes burn 20gph. This was due to a faulty O2 sensor.

Re: yamaha ox66 250 fuel consumption

Yamaha actually has performance tests on many many boats. Here is one on the Marlin with 250 OX-66 engines. Just remember, their condtions are usually ideal, light, and smooth. Add a full fishing load and some seas and mileage is going down. I looked at the pursuit test, and it is just like Yamahas. Yamaha was running in 5mph winds, and Pursuit was running a river with light winds also. Naturally their mileage is gonna be better than yours. Throw it offshore in some chop and its going down. Is your 1 MPG the overall trip average? Or is that what you are getting at cruiseing range of around 4000rpm? If it is the average for the whole trip, then thats about as good as it gonna get. If it is at 4000rpm only, then you may need a good tune up, but dont expect 2mpg out of your combo. You can either live with it, or upgrade to 4 strokes, even some of the lastest direct injection 2 strokes.

http://www.yamaha-motor.com/assets/...in_otb_2StrokePerf_OX666_250hp_0190-GRW-Z.pdf