Trying to Max. fuel mileage

Bullet[BS]

Recruit
Joined
Jul 31, 2005
Messages
5
Hello everyone, I have a '79 Mercury 115 hp. I am looking to find what RPM's will give me max. fuel economy. For now I have been running it around 3800 rpms. Running the stock aluminum 3 blade prop. Any help is appreciated.
 

Ben Konopacky

Petty Officer 1st Class
Joined
Apr 5, 2004
Messages
296
Re: Trying to Max. fuel mileage

I don't go by RPM, just get the boat on plane w/trottle forward then back the trottle off just to maintain speed on plane.make sure the eng. is proped correctly.
 

JasonJ

Rear Admiral
Joined
Aug 20, 2001
Messages
4,163
Re: Trying to Max. fuel mileage

There is a point where the engine sounds kinda gravelly, then as you advance the throttle, it suddenly sounds smooth. It is this point that you will realize the best economy. On my setup, this is achieved around 3800 rpms, depending on load. It is also true that minimum planing speed will give decent results, but you want the engine working within its powerband, and minimum planing speed may be too slow on your setup. I know on my setup minimum planing speed is too slow, and I have yeilded less than optimal economy at that speed. You could try some experimenting as well. It is hard to give a set number, because it can vary from trip to trip, even day to day. Good luck...
 

Bullet[BS]

Recruit
Joined
Jul 31, 2005
Messages
5
Re: Trying to Max. fuel mileage

Thank you for the info guys, and Jason...Thank you for your service and your help. I will get back to you guys and let you know the results. So far on about 7 gallons of fuel I can make a 20 mile trip that is if my trip meter is accurate on my X-65. We'll see.
 

JasonJ

Rear Admiral
Joined
Aug 20, 2001
Messages
4,163
Re: Trying to Max. fuel mileage

Thats about what I end up using, 6-7 gallons in a 22 mile trip (depending on conditions). You may just be about as efficient as you are going to get unless you swap the motor onto an aluminum hull. That'll give some good economy there...
 

imported_scott_m

Petty Officer 2nd Class
Joined
Oct 24, 2004
Messages
139
Re: Trying to Max. fuel mileage

And another alternative is to invest a couple of hundred dollars in a FloScan - then you can monitor your consumption vs. RPM vs. conditions in real time and adjust accordingly.
 
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