70 hp mercury fuel consumption

[Toddo1969]

Im dealing with a high fuel consumption issue with my motor the serial number is 5693462, I think it's a 1982, with the cover off how much fuel should be passing through the main jet in the center of the carb? I look in the carb throat at full throttle and there seems to be a lot running through. also im experiencing loss of power at full throttle it takes a bit to get on plane. just changed the switch box and still no change. any help will be greatly appreciated

 

[roscoe]

First of, what do you consider to be " high fuel consumption."

That motor could easily use 5 or 6 gallons per hour, at full throttle.

No way to measure fuel flow by looking at it.

A problem that will cause huge fuel loss is a bad fuel pump diaphragm.
If it has small hole(s) in it, it will leak fuel into the crankcase, wasting fuel and causing a flooded running condition.
Rebuild fuel pump. $20 for parts.

Then tune the carb to specs.

 

[airshot]

Yep it sounds like something is not working correctly. About time for a thorough go thru on that motor. The rule of thumb for most two cycle outboards is 1 gal of fuel per hour at WOT for every 10 hp. Your 70 hp should be using approx. 7 gallons per hour at wot. Cut that in half for a typical cruising speed of approx. 3200-3400 rpm. These are just general rule of thumb estimates and I have found them to be pretty close in my 50 yrs of boating.

 

[Toddo1969]

Thanks for your input going to buy the fuel pump rebuild kit today.