"Got a question passed along a
"Got a question passed along about "how much will/should my outboard burn".
There is not a "one size fit's all" answer to that question. There is so many variables that the answer will not be the same for identical boats with identical motors. But there is some "rules of thumb".
IF your boat is fitted with a motor whose horsepower is 80% of the maximum rating for your boat and the propeller pitch has been matched to the "normally loaded" rig (eg. Max rated for 125 horse - 125 x .8 = 100 horse), then at wide open throttle (WOT) you can use the formula HP x .1 to get the average gallons per hour it will burn.
(too much motor on a boat - more than the 80% rule will result in a little more speed, but at a disproportiate increase in the amount of fuel burned - likewise, to little horsepower, which is typical with the "stock" motor on many package deals, will result in poor performance with far more than average gas consumption for that model of motor - you can't push a 1400 pound boat with a 50 horse - not if it's a planing hull)....
So for the 100 horse - 100 x .1 = 10 gallons per hour (or 10% if you like).
Every motor has a sweet spot. This can be determined on a non-computerized ignition by determining when the motor reaches maximum timing advance but not full throttle. If you pull the hood off your motor and without the motor running, advance the throttle and observe the linkage going to the trigger/sensor. You will notice it stops moving before you have reached full throttle (approx 2/3's of full throttle).
On most motors that will be approx 1500 rpms below your WOT rpms.
On alot of Johnny's/Ev's that will be around the 4000-4200 rpm mark.
At max timing advance, but not max throttle, the motor only burns about 40% of the fuel it would consume at WOT. The speed that the boat is travelling at that point is considered it's "cruise speed".
So for the example 100 horse motor that burns 10 gph at WOT, it should only burn about 4 gph at cruise.
I do have a number of (floscan) tests for a wide range of motors and despite all the hype and advertising as to how efficient 4 strokes are, on water tests do not support the claims and actual data shows that a 90 horse 4 stroke at WOT burns about 9 gallons an hour, just the same as an old pollution spewing, carburated 90 horse 2 stroke.
I will have a dig through my computer files to see if I have some test charts specific to OMC/BRP engines and post them on this thread for those who are interested - most of my data is for Merc's/Yami's and Honda's.
A couple of other myth's -
A hydrofoil will NOT improve your overall gallons per hour if you run at any speed above the minimum speed required to get on plane.
Running a prop with more pitch than your motor can properly handle will NOT make it go faster and it WILL burn alot more gas."
"Got a question passed along about "how much will/should my outboard burn".
There is not a "one size fit's all" answer to that question. There is so many variables that the answer will not be the same for identical boats with identical motors. But there is some "rules of thumb".
IF your boat is fitted with a motor whose horsepower is 80% of the maximum rating for your boat and the propeller pitch has been matched to the "normally loaded" rig (eg. Max rated for 125 horse - 125 x .8 = 100 horse), then at wide open throttle (WOT) you can use the formula HP x .1 to get the average gallons per hour it will burn.
(too much motor on a boat - more than the 80% rule will result in a little more speed, but at a disproportiate increase in the amount of fuel burned - likewise, to little horsepower, which is typical with the "stock" motor on many package deals, will result in poor performance with far more than average gas consumption for that model of motor - you can't push a 1400 pound boat with a 50 horse - not if it's a planing hull)....
So for the 100 horse - 100 x .1 = 10 gallons per hour (or 10% if you like).
Every motor has a sweet spot. This can be determined on a non-computerized ignition by determining when the motor reaches maximum timing advance but not full throttle. If you pull the hood off your motor and without the motor running, advance the throttle and observe the linkage going to the trigger/sensor. You will notice it stops moving before you have reached full throttle (approx 2/3's of full throttle).
On most motors that will be approx 1500 rpms below your WOT rpms.
On alot of Johnny's/Ev's that will be around the 4000-4200 rpm mark.
At max timing advance, but not max throttle, the motor only burns about 40% of the fuel it would consume at WOT. The speed that the boat is travelling at that point is considered it's "cruise speed".
So for the example 100 horse motor that burns 10 gph at WOT, it should only burn about 4 gph at cruise.
I do have a number of (floscan) tests for a wide range of motors and despite all the hype and advertising as to how efficient 4 strokes are, on water tests do not support the claims and actual data shows that a 90 horse 4 stroke at WOT burns about 9 gallons an hour, just the same as an old pollution spewing, carburated 90 horse 2 stroke.
I will have a dig through my computer files to see if I have some test charts specific to OMC/BRP engines and post them on this thread for those who are interested - most of my data is for Merc's/Yami's and Honda's.
A couple of other myth's -
A hydrofoil will NOT improve your overall gallons per hour if you run at any speed above the minimum speed required to get on plane.
Running a prop with more pitch than your motor can properly handle will NOT make it go faster and it WILL burn alot more gas."
