gas drinking motor

[truckdrivinnut]

I have a 1977 evinrude 85 horse outboard on a dixie bass boat of the same model. I am running 87 octane with 50:1 mix of johnson/evinrude oil. Just out riding around or tubing I am using around 6 gallons an hour. Is this normal?

 

[dingbat]

Re: gas drinking motor

That's about right. For WOT opertion figure 10% of your horsepower rating.

85 Hp = 8.5 GPH

 

[truckdrivinnut]

Re: gas drinking motor

thanks for info. also on this boat i am only running at about 32mph does that sond right? It is a 16 ft. tri hull.

 

[steelespike]

Re: gas drinking motor

thanks for info. also on this boat i am only running at about 32mph does that sond right? It is a 16 ft. tri hull.

Would seem to me about 40 would be closer to right.Many things contribute to your final, speed.What is the rpm at speed.Speedometers are notoriously inaccurate. speed by GPS is the only way to tell.Have you tried trimming the motor for best speed?Is the bottom clean,is the antivent plate(just above the prop) approximately even with the bottom of the boat.Have you checked your compression?Is the throttle opening all the way?What is the condition of your prop?What size is prop -- X --? Usually stamped on the prop.

 

[truckdrivinnut]

Re: gas drinking motor

Everything is in check with what you said. I am running 5000-5200 at WOT. I have not checked the compression, right height on motor, prop has very few MINOR dings nothing major. Tilt and trim is out of comission right now but boat planes out almost perfectly. prop size is not stamped but appears to be somewhere in the 17-18 pitch range. bottom is clean.

 

[chainsawjunky]

Re: gas drinking motor

I don't run WOT all the time and my boat is almost like yours. It's a 1977 glastron tri-hull with mercury 85 hp and mine gets a little less than 2 hours on one tank of gas(6 gallons). According to my speedometer(probably off) it tops at 31mph and I usually run it between 25-30.

 

[steelespike]

Re: gas drinking motor

Everything is in check with what you said. I am running 5000-5200 at WOT. I have not checked the compression, right height on motor, prop has very few MINOR dings nothing major. Tilt and trim is out of comission right now but boat planes out almost perfectly. prop size is not stamped but appears to be somewhere in the 17-18 pitch range. bottom is clean.

I think I would start with actual GPS speed.
Antivent plate even with bottom is a starting point.Try raising motor one hole at a time until venting becomes a problem.An inch could give you 2 to 3 mph.Keep an eye on pumping water.
Once you have the height and trim set then you could try some props usually a dealer will let you try them if you intend to buy.
Over at the prop forum They can tell you your pitch based on number off prop then they can tell where you are at based on GPS speed and rpm.
I'm not an expert but it just seems to me you should be running closer to
40 again over at the prop forum they can figure that as well.

 

[kenmyfam]

Re: gas drinking motor

I have a 1977 evinrude 85 horse outboard on a dixie bass boat of the same model. I am running 87 octane with 50:1 mix of johnson/evinrude oil. Just out riding around or tubing I am using around 6 gallons an hour. Is this normal?

Thats pretty much normal for that size motor.