1989 120 Looper 3MPG???

[countvlad]

last trip was 15 miles and it burned about 5.5 gallons.... i would say thats normal if i was runnig wide open but but i didnt, i cruised doing aprox 4500RPMS with the motor trimmed up....

carbs have just been rebuild, getting ready to change the spark plugs and wires... timing @ WOT is correct 18 BTDC... i was using regular gasoline with no ethanol..... recirc check valves were also changed...

WOT RPMS 5900 and i have a SS prop

is this about right 3mpg? at cruising speed?

 

[Lion hunter]

Re: 1989 120 Looper 3MPG???

Boats are calculated in gallons per hour. A common estimate used on here is 10% of the hp rating. Your estimate would be 12 gal per hour at wot. How long did it take you to travel 15 miles. How much weight was in the boat? was it against the current?

 

[countvlad]

Re: 1989 120 Looper 3MPG???

Boats are calculated in gallons per hour. A common estimate used on here is 10% of the hp rating. Your estimate would be 12 gal per hour at wot. How long did it take you to travel 15 miles. How much weight was in the boat? was it against the current?

to travel 15 miles it took me about 25 mins.....
weight of the boat including myself and gear aprox 2000lbs....
no, it was not against the current....

well 10% of the hp rating would be 12GPH which is pretty close to what im getting but my concern is, should i be getting slightly better mileage at lower RPM than at WOT?

 

[Lion hunter]

Re: 1989 120 Looper 3MPG???

I would say if your in the ballpark it's probably right. There are so many variables that i would be hard to ever be very accurate. I think you would have to measure fuel use over a period of time and average it to get actual use. I wouldn't change antthing drastic from just one reading.

 

[d.boat]

Re: 1989 120 Looper 3MPG???

As far as MPG, I've never done much better than that, but mines 200 hp running a jet l/u.

But as far as gal/minute, it seems a little high to me for the RPM's you're running. My calculation is that you're burning around 13/hr if you burn 5.5 in 25 minutes. As someone said, a rule of thumb is that you burn 10% of HP at WOT. That rate should be the same regardless of running conditions (current, wind, load, etc), but your speed of course would vary (and therefore the MPG). But RPMs is RPMs and that's what determines the GPH burn rate.

As an example, my jet burns essentially the same as my friend's prop'd unit at similar RPMs. He's going faster though since his prop is more efficient than my jet. Therefore he gets better MPG for the same GPH burn rate.

But, you're doing even more than the 10% of HP rate at substantially less RPMs.

For grins, run 30-60 minutes at WOT and accurately measure the gas used.

 

[Fl_Richard]

Re: 1989 120 Looper 3MPG???

Loopers LOVE fuel!

 

[Israel Hands]

Re: 1989 120 Looper 3MPG???

My 87 140 Looper only gets 2.8MPG. Good compression and it runs like a top!

Israel Hands

 

[tashasdaddy]

Re: 1989 120 Looper 3MPG???

there are many variables, you need to be properly propped at WOT, to get decent performance at other speeds. if no it causes lugging.

 

[countvlad]

Re: 1989 120 Looper 3MPG???

there are many variables, you need to be properly propped at WOT, to get decent performance at other speeds. if no it causes lugging.

i havent been out on the water past week or so but i didnt think 5800-5900 WOT was bad with just me in the boat....

before i got the tach to work i used to have an 19p alum prop and i was turning about 4800-4900 rpms

so im thinking this 15p SS is the one...