burned 20 gallons of gas just 48 miles. 21 pitch prop HELP.

[alphaman]

Ok. 112 Johnson on my 17ft predator bay boat. I have a 21 pitch prop on it, Boat takes for ever to get out the hole. But once on step I'm good. Well to top it off tool it out sat. Ran around the bay. 48 miles total. And emptied the gas take. Had about 20 gallons of gas. That has to be VERY BAD. TO BURN 20 gallon in 48 miles. I'm thinking that prop has to go. Prob need a lower pitch. 19 perhaps?

[jchief]

rpms at wide open?

[alphaman]

Just about. Runnin 4500rpms then backing off until she plains out. Once on step. I'm at 4000 and 23-26 mph.

[jchief]

Not a mechanic, but most motors need to turn between 5000 - 5500 rmp @ WOT. If you run it WOT how many rpm are you turning? Sounds like a lower pitch would help some. Montauk is probably the best on the site to give info.

I think you may have another problem burning that much gas. Is tank built in? When did you fill up? How much do you normally use?

I know, more questions than answers.

[alphaman]

Wot. 5300 I think. I know it's above 5000. And it an custom 30 gallon alumTank.

I think I should put a small pin hole in the gas cap. Cuz it suckin hard to get gas cap. It just a PVC plastic cap. When I would open the gas cap the air rushes out. Maybe that will help the gas flow. Air to fuel ratio. Not getting any air flow. That's y I was burning that much gas.

First time out With the boat. Just bought it. I put 25.7 gallons in the tank wed night. Ran it for 15 min. In the bayou thur. And fri. Then in the bay sat. Didn't fill it up though.

[jchief]

Thought was someone may have needed some gas and helped themselves or it leaked out prior to trip.

Don't know what the motor should turn WOT but I think you are close. Going to a 19P will add about 200 rpm at WOT.

Would definately do something with the lid/vent.

[alphaman]

That's what im thinking. Better airflow though the tank and lower pitch would help really help! My gas milage. I figured I got 1.7 mpg. This weekend that's just ridiculous. Should get at least 3.

[Montauk17]

That motor needs to turn 5500 rpm's at WOT. You will need a lower pitch for sure if your holeshot is not what it should be. My suggestion would be to run it WOT to make sure what your rpm's are. Also,if the motor is mounted too low on the transom can cause the motor to be low on rpm's. A OMC v4 motor is not the best on fuel to begin with so dont expect a big increase in mileage.

[alphaman]

Thanks fellas. I'll try it out. Drop to a 19 pitch and drill a little pin hole in the gas cap. To get some air flow through the tank. Maybe I'll get 2 mpg. After that.

[alphaman]

19 pitch save me plenty of gas with my omc 1996 112 johnson. I went 40 miles and burnt only a quarter of tank gas vs. That 21 pitch in 48 miles I ran out of gas. That is so much better!!!

[alphaman]

And she gets on step very quick with that 19 pitch prop. No struggling to get out the hole. So all is well with my predator!!! By the 3 trip all prob. Had been ironed out. Thanks for all the advice.

[Montauk17]

Cool deal glad it worked out for you.

[rambler]

i tried to PM you...looking for some more fuel problem help/advice...