Fuel Economy

[ken-w]

Friend has a Tracker/Force 40 hp that pushes a 20′ pontoon around a small lake with a speed limit of 5 mph. I sucks the gas like its pulling a skier. How can he get better fuel economy from it? Besides moving over to 4 stroke can anything be done?

[retiredoz]

I’d try running a prop with a lower pitch ? Unless you tried that already.

[fleetwin]

Well, most of those pontoon boats have a certain hull speed, pushing the throttle down farther after reaching that speed usually does nothing more than lug the engine and waste fuel. You mention the speed limit of 5mph, I would guess your friend is trying to exceed that limit.
Definitely have a look at the prop, you may need a different pitch for such a specific application. Some manufacturers make special "hi thrust" props for pontoons/no planning hulls. Has the pontoon boat been pulled out of the water lately? Perhaps the pontoons are fouled with marine growth or full of water. The prop may be beat up or have a spun hub as well.

[ken-w]

Looking to sip gas at idle not gulp. Waiting on carb kit right now but what about changing the main jet out?

[crosbyman]

my merc 50 Classic (45 HP) would burn 5 gal /hout at max rpm and troll all day on 5 gal /600 rpm

my 75 Etec burns .6 l/trolling or about 2 gallon to troll all day (4.8l 8hours)…. ok le’s say 2.5 gallons a big improvement on my carb Merc 50

your friend’s carbed …ported engine is pushing gas and oïl out the exhaust ports every down stroke.

he needs an ETEC !

Joining AOMCI has priviledges 🙂

[fleetwin]

No, I wouldn’t mess with the high speed jet unless you feel someone has changed it to some other size. In any event, the high speed fixed jet won’t really affect low speed fuel consumption.
Are you sure there isn’t some sort of fuel leak? Would be tough so see buried down in back of a pontoon.

[vintin]

Running that motor so slowly probably has a lot of condensed fuel being dumped into the lake via the crankcase drain reed valves. Recovery systems are not difficult to install. This may or may not apply to the Mariner you are asking about. Maybe a 5hp pony motor would be a good idea.

[garry-in-michigan]

There were smaller motors that would give you the five miles an hour …

. . . . . 😀

[ddoyle]

Yeah get a motor/prop/gear box that matches the task.

Your friend is lucky that the lake speed limit just about matches his boat’s max displacement speed. On paper it should take 5 hp to move a 2k pound 20 foot hull thru the water at the speed limit. Get an engine that produces 5 hp at 1/2 -3/4 throttle and you should be as efficient as possible with some reserve for wind, extra ladies etc.

A classic black merc 7.5 (with merc’s work boat/displacement prop) maybe? sexier,lighter,simply better then a modern 4 stroke.

[jerry-ahrens]

I’ll bet the prop pitch is too high. Take a look at what is available through Quicksilver parts and accesories. If the boat has a tach, check the RPMs at full throttle. The engine should hit 5000 at full throttle. I’ll bet it doesn’t with a 40 hp. Anytime you ”lug” an outboard expect it to guzzle the fuel.

[Author]

Posts