Fuel consumption

[Max]

Down on Lake Texoma this week chasing stripers.  I knew I was low on fuel so I purposefully pottered around outside the marina until the engine quit.  I motored in on the 5-horse Nissan kicker, loaded up on the trailer and went into town for gas ($2.65 vs. $3.69 at the marina!).  I then ran the boat for the next two days of normal running and gunning mixed with some idling speed.  Loaded the boat up and topped off the fuel.  Here are the specs and the resulting questions--

Boat: 1986 20' Osprey
Engine: 2000 115 Merc
Fuel cap: 40 gal
Miles run (by GPS): 128 @ an average 25 mph @ 3800 rpm
Fuel used: 31 gal

That works out to roughly 6 hours engine time (allowing for idling) and 5 gallons per hour. Does this meet the common sense test?  and, if so, is this about normal?  BTW, I WILL put an hour meter on as part of my winter console rebuild project...

Max

[RickK]

Welcome aboard Max  :!:  :!:

.... and 5 gallons per hour. Does this meet the common sense test?  and, if so, is this about normal?  BTW, I WILL put an hour meter on as part of my winter console rebuild project...
Max

That's about what my 115 uses on my 170 if I run it at cruising speed (30ish) for an hour straight - 5-6 gals/hr.

[Keith Knecht]

Looks right to me.  Rule of thumb by an old outboard mechanic.  Take the horsepower and move the decimal one place to the left.  For a 115 that's 11.5 GPH at full throttle.  Cut that in half and you get an average crusing consumption. 5-6 GPH.  Your test seems to be right on the money to prove that old mechanic knew what he was talking about.

[DavzBoat]

That's about what mine gets, Keith.  Good rule of thumb... I'll remeber that one.

[riverratjr]

my 222 w/150 merc w/carbs uses 5 gals/hr @ 2200 rpm. your numbers look good from here. a hour meter is a wise investment. :)

[JimCt]

Now that I think back on my Merc 75hp rate of burn,  the formula hits it about right.

[John Jones]

Sadly, it holds true for my 225 Johnson.  23 gph by the fuel flow gauge.