75hp poor gas mileage

C

Camaro guy

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Joined
Jul 17, 2013
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2
Hello guys .. I'm very new to this.. I have a 1969 Chrysler sport satellite with a 70hp of the same yr. I fixed all the fuel leaks and rebuilt all 3 carbs.. It runs awesome. Idles smooth and plenty of power.. BUT it will burn through two 6 gallons of 50/50 mix with 91octane in about 3hrs just cruising.. (Cruising is at about 3/4 throttle ) Is this normal for this engine ? At WOT it will go about 33 to 35 mph ?? Any help is greatly appreciated !!! Not sure if the prop is stock ? Thanks !
 
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jerryjerry05

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,927
Re: 75hp poor gas mileage

Welcome, Gotta figue out the rpms at WOT.
Then what prop is on the motor.
Set up right,with a normal load.
1-2 people a cooler and gas and gear.
You should be running about 53-5500 rpm at wot.
33-35 for a 70 is actually pretty good.
 
Frank Acampora

Frank Acampora

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Jan 19, 2007
Messages
12,004
Re: 75hp poor gas mileage

The rule of thumb is that outboards use about 10% of their horsepower in gallons of fuel at wide open throttle. Figure about 7-7 1/2 gallons per hour at wide open throttle and a little less at cruise. SO: Your engine is normal and maybe getting a little more than expected.
 
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C

Camaro guy

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Joined
Jul 17, 2013
Messages
2
Re: 75hp poor gas mileage

Ok thanks for the help !!! I couldn't understand how it always just ran so good !! But that's what it should be getting !! Thanks again !
 
NYBo

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
Re: 75hp poor gas mileage

Welcome to iboats!:welcome:

If you want to save a little gas money, switch to 89 octane. You could probably get away with 87.
 
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