Mileage

Themanofsteel

Petty Officer 1st Class
Joined
Jul 11, 2015
Messages
312
I have a 1989 Force Outboard 85hp. Does anyone know what the average miles per gallon should be?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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47,296
will depend on what it is pushing (load). use 2 MPG as a rule of thumb and be happy if you get more.
 

Themanofsteel

Petty Officer 1st Class
Joined
Jul 11, 2015
Messages
312
I figured it's getting about 1 mpg. Approx. Is there any way to improve mileage?
 

HotTommy

Lieutenant Junior Grade
Joined
Mar 15, 2013
Messages
1,025
As Scott said, the answer to your question is more about the load you are moving than the engine that is pushing it. Unless the engine is badly out of tune or driving a bad propeller, any improvement in MPG will come from changes to the boat or how you operate it. .... The old rule of thumb is to expect to use about one gallon of fuel per hour for every ten horsepower. So an 85 HP motor at full throttle should use about 8.5 gallons per hour. If you are getting about 1 MPG, that means you are going about 8.5 MPH at full throttle. That sounds like you are pushing a very heavy load on something like a pontoon boat. ... What kind of boat are you driving?
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
The other thing to check is the engine rpm at WOT (wide open throttle). It should be around 5000 RPM. If it is way less it means either the engine is misfiring, pushing too much of a heavy load or it could just be the boat is not properly trimmed (boat is plowing) and finally it could be the propeller is of the wrong size and pitch. Personally, unless you made changes to the prop, it should be the right size. So look into misfiring first and next experiment what is the proper trim for the boat to be efficient through the water.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
47,296
Bayliner made the Capri from 16' to about 24'

also, bayliner capris are known to get water logged. you could be carrying 800# of extra water which would impact performance and fuel economy.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,923
Load, propeller, rpm's.
​Load: 1-2 people, 1/2 tank of fuel,small cooler and CG equipment.
Prop: good condition no nicks or bent blades.
Rpm's: running wide open hurts the economy.

I have twin 88/85's on my 21 center console.
I run with about 40gal.(I go out 15-20 mi.) and never need more than 25gal.
I usually run 2-4 people and 2 coolers.1 for food and drink the other for bait, fish.
Also the normal equipment, rods and tackle boxes etc.

I usually get about 2.2-2.4 mpg.

Running wide open cuts that way down to 1.3mpg.

​I cut up and took to the dump the same model boat as mine.
I found about 800# of soaked foam.
 
Last edited:

SkiDad

Lieutenant Commander
Joined
Jul 18, 2010
Messages
1,518
i average about 3 mpg on my boat when pulling skiers in the 3700-4300 range. This is about 1500 rpm below full throttle and seems to be a happy spot. If i go full throttle it probably gets 2 mpg. And i agree with what Jiggz said about prop and trim - i think my boat does better with lower pitch prop - it was propped for only 4700 rpm when i got it and now i have it propped for 5200-5500 depending on what prop i put on.
 
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