1973 Mercruiser 165, 6 Cylinder inline 250 cubic inches fuel consumption?

[Weirdnerd]

Hi again, after year and a half of tinkering with my Sea ray, finally took the boat to the lake, I am getting on plane at 2700 RPM and goes fast at 4000, I am planning to take the boat for a long trip ( around 200 miles) and I have 30 gallons fuel tank, I still don't know the boat so good, and I know I will have to refuel somewhere to be safe.




I would like to know if someone knows what is the average fuel consumption on the engine?, I know it is a function of time, but it would give me an informed opinion on how much will it drink per hour .

 

[jimmbo]

At WOT you will probably burn about 9 gal/hr. but when run at it's most economical speed it will probably burn about 5 - 6 gal hr. If 4000 rpm is your top rpm, then you are slightly over propped. Without knowing what speeds you are going, an estimate of MPG is impossible

On my boat if I go WOT I can use 33 gals in about 90 minutes, but I will cover more than 90 miles, If I slow down to 35 - 40 mph, I will increase the distance considerably, if I drop it down to 23 - 24 mph, it will get its best mileage, almost doubling it range.

 

[Bt Doctur]

Your going to need a bigger gas tank for 200 miles
When I had my SR W twin IL6`s , high comp heads, weber 4 barrel My slow setting was 2500 prm @ 31 MPH @ 7.5/G per Hr total . When I stepped it up some to 4550 my speed was 62 mph and my fuel burn was 39 G/ hr total

 

[Scott Danforth]

0.4 lbs of fuel per hp per hour

 

[kenny nunez]

The only other thing you could do would be to add a Fuel Flow Meter and a vacuum gauge which would give you the “sweet spot” for maximum fuel mileage.
Also the correct propeller to get the rpm to the 4400 range.
As the Doc said, you will need extra gas.

 

[Weirdnerd]

I have a vacuum gauge, will check about that, also, the previous owner had two 17 pitch props with it, so I am not in a hurry to change propellers ( I am a "Conscious shopper") , on the 200 mile thing, lake Powell has a gas station halfway the channel ( around mile marker 50 either way) I am planning to refuel there twice, and once on the other Marina ( three refuels on the round trip) no need for a bigger fuel tank.


I am not concerned about Miles Per Gallon either, I know that fuel management is a matter of time and rate of consumption, and on boats there are many variables, wind, drift, currents, etc, so mileage is a changing thing depending on those variables... Just wanted to know if there is a chart with RPM and fuel flow per hour so I can base my trip on that.

 

[Weirdnerd]

0.4 lbs of fuel per hp per hour

So that will get me on the 10.5 gallons per hour area at full power ( Assuming the 1973 Mercruiser 165 can develop 165 HP?)

 

[Weirdnerd]

Your going to need a bigger gas tank for 200 miles
When I had my SR W twin IL6`s , high comp heads, weber 4 barrel My slow setting was 2500 prm @ 31 MPH @ 7.5/G per Hr total . When I stepped it up some to 4550 my speed was 62 mph and my fuel burn was 39 G/ hr total

What size and hull shape was your boat?, just for comparison sake.... Also, 39 gallons per hour was on only one or the two engines total fuel flow?