2002 Mercury 150xl Saltwater Fuel consumption

[Jetkiller]

Fellow 2 strokers, I have a 18 1/2' Off Shore Dynasty with a 2002 Mercury 150xl on it. Lately my fuel usage has really go WAY down. I'm only getting about 1 MPG ??? The boat & motor are less than 1400lbs and I'm just running around 4200 rpms. Any thoughts or input r than a new motor?? thanks

 

[Chris1956]

Check for leaks. A steady drip-drip-drip adds up.

Check the spark plugs and see if they are black with fuel. If carb motor, check the see if the enrichener is stuck open. Check to see if the fuel pump is leaking internally or externally.

 

[Scott Danforth]

First, welcome aboard

2-stroke outboards burn about 0.55# of fuel per HP per hour (BSFC). This is crankshaft HP, not prop HP

make sure to weigh your boat. reality weight and catalog weights are two different things.

however lets assume that you are putting out 135hp at the prop at your 4200 RPM. that is about 150hp at the crank. 0.5#*150 is 83# of fuel, or 12 gallons of fuel. How far did you get in that hour? Did you burn more than 12 gallons?

things that effect burn rate:

• too high a pitch prop
• too heavy a boat
• trim tabs down
• wrong tilt/trim angle
• wind
• current
• dirty bottom
• running rich (carb issues)
• motor compression
• bad plugs

in addition, you could be leaking

 

[dingbat]

Something is not right.

I’m getting 1.9 gpm on a 200 hp pushing a #5k boat @4400 rpm

Fuel would literally being running out of the motor and pooling somewhere to be using that much fuel.

What is your speed at 4,200?
I run 27 kts. at that rpm

 

[airshot]

Why not start at the basics, do a compression check to make sure your engine is healthy. Then look for leaks, pump, hose, squeeze ball...have saw many develope small cracks that leak fuel, connections/ clamps, just found a small leak on my OB on the shake down cruise for the start of the season. Clamp around the fuel line had a drip, replaced with new clamps.. Fuel is going somewhere....