Optimizing for 2 cycle fuel economy

[taleon]

I have a 1990 Force 50 I just got going, mounted on a Lund 16? Mr. Pike. I was very excited to get the motor going and it runs great, only to be disappointed by the apparent fuel economy. I changed plugs. Have a new prop (10 3/8? by 14 ??) on the way, not yet mounted. I can?t read what the current prop is as it?s beat up.

I?m going to check / adjust the low speed idle jet this weekend. I don?t believe this motor has an adjustable high speed jet. I?ll check the timing and set that.

I?m getting 3 ? 3.5 mpg best guess using Magellin?s Map Send Streets software to re-plot my two weekends of running. I have power tilt / trim, but don?t have a tach. Although the motor didn?t sound to be over tach?d. Actually sounded about right. I only got 27 MPH max with one other 180lb person in the boat. I do have a 9.9hp kicker and an electric motor on the boat adding some weight. Total extra weight with all, excluding the 50 is probably about 600lbs. I would think this thing should get North of 30 MPH?

I?m heading to Quebec in 10 days for an 8 day remote trip. The Island we stay at is 20 miles by water and water is the only access. I?d sure like better fuel economy. Any thoughts about what else I can do to optimize the fuel economy? Do you think I should get more than 30 MPH? Do you think the prop will make much difference? I forgot to mention compression is good at 140lb / cylinder.

Thanks
Tim

 

[Scaaty]

Re: Optimizing for 2 cycle fuel economy

Force's like gas WOT...'bout all ya can do is throttle back a bit

 

[JB]

Re: Optimizing for 2 cycle fuel economy

You could replace that beat up prop. Drag uses fuel.

 

[jerryjerry05]

Re: Optimizing for 2 cycle fuel economy

Put a tach in the system.Check rpm at wot and get back with the results.
You should run at about 5200-5500 rpm loaded.Jerry

 

[Frank Acampora]

Re: Optimizing for 2 cycle fuel economy

DO NOT mess with the low speed needle in an attempt to get better fuel economy. You will do better by leaning it but you WILL also melt piston(s). Believe me! I learned that lesson the hard way on a cruise to Canada many years ago when I was still wet behind the ears.

27 MPH at WOT is just about right for that engine on a 16 footer. You may find the 14 pitched prop is just a tad too much and while your fuel usage will decrease a little --just as if you had overdrive in an auto--your top speed will also suffer a bit.

Throttle back to a cruise speed of 20-22 MPH and you should cruise for about 2 hours on a 6 gallon tank. That's not too shabby.

On calmer water, trim the engine out 'till just before the prop starts to cavitate. This helps lift the bow out of the water for less drag and better fuel economy. In heavy water, trim in to have the bow cut into the waves and minimise pounding.

ALSO, BE SURE TO USE THE RULE OF THIRDS: 1/3 fuel to get there, 1/3 to get back, and 1/3 in reserve. Buy another 6 gal tank at Wal-Mart for 15 bucks and 5 bucks for the male fitting. --Cheap insurance!

 

[roscoe]

Re: Optimizing for 2 cycle fuel economy

A 13.5 or 14.5 prop may be ok.
Make sure that kicker is COMPLETELY out of the water while underway with the main motor.

2/3 throttle will save you half the fuel over full throttle.

27 mph is right for that load.

You better find a way to haul 40gal of fuel for the trip.

 

[taleon]

Re: Optimizing for 2 cycle fuel economy

I appreciate all the replies. I didn?t figure there was any magical fix out there, but thought I?d make sure. Throttling back to 20mph will help and I think the new prop should be noticeable. Since we were mostly test running we did have it WOT most the time which is eye opening when you start looking at fuel. I?ll make sure the jetting is set per mfgr?s recommendations this weekend and verify the timing also.

I have lots of gas cans and was planning to bring 35-40 gallons which adds a lot of weight, but you got to do what you got to do. I was looking at tach?s and see most are for 3 cyl and up. Does it really matter how many cylinders? One would think it would matter if it has 2 cycle or 4 cycle, but not the number of cylinders.

Thanks

 

[ezmobee]

Re: Optimizing for 2 cycle fuel economy

The tach reads the poles of the alternator/stator so it has nothing to do with 2/4 cycles. I think Forces have different # of poles than other outboards so make sure you get a tach that will work with your Force.

 

[jim_b_20653]

Re: Optimizing for 2 cycle fuel economy

Most tachs will not work with Force. Force motors use a 12 pole tach, most other manufacturers use between 2 and 6 poles,so make sure you buy one that is designed for Force. Number of clyinders in not important.