recently I purchased a 1997 Mercury Mariner 175 hp EFI. It runs on a 19 foot Sylvan aluminum.


Unit runs great but ....

I get about 2 miles per gallon or about 12 gallons per hour.

I run it at 3500 RPM which is around 28 MPH.

The engine will rev to 5500 and get close to 50 MPH so my mechanic says all is working

Is this what to expect?

Go back to Mecury (website) and see if they have the orignal information about that engine. I was able to get the fuel consumption on a test boat they had used on my engine. about 3500 (26-28 mph) is where the sweet spot is.

you should run at cruising speed which is about 4600rpm and will find that engine fuel consumption should be lower. 12 gall per hour is the consumption for carb version.