Fuel Efficient Outboard Choice

[lowell7963]

General question. On a poontoon, would a 90HP running at say 1/2 throttle, be equivalent to a 50HP running wide open?

I guess the question is if I upgrade to a bigger motor can I choose to run at less throttle and get about the same speed and fuel usage, or does the big guy just use more fuel at the same speed. Of course assuming the 90 is propped properly.

 

[Silvertip]

Re: Fuel Efficient Outboard Choice

It might be close, but when you are used to having 50 HP and you suddenly have 90 to play with, guess what happens. You got it, you will use it. The down side to this is that because you have nearly double the HP you will not realize anywhere near double the speed. So if you are very careful with the throttle and operate like you say you will, then you might get close to the same fuel economy. But abuse the throttle to get a even two more MPH will cost you in fuel. Pontoons are much different than planing hulls when it comes to performance. Another down side is that with the 50 you can just putt along and burn probably 1/2 the amount of fuel you would at WOT. You can't even come close to that with the 90.

 

[H20Rat]

Re: Fuel Efficient Outboard Choice

in theory the best operating range for a 4 stroke engine is at WOT running at the peak torque rpm. (actually it is with no throttle plate even, permanent WOT)

So you would think that if you are your peak torque rpm on the 50, you would get better efficiency.

 

[gss036]

Re: Fuel Efficient Outboard Choice

"in theory the best operating range for a 4 stroke engine is at WOT running at the peak torque rpm. (actually it is with no throttle plate even, permanent WOT)

So you would think that if you are your peak torque rpm on the 50, you would get better efficiency.
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I disagree with your theory. I just went from a 200 hp Mercury 2 stroke to a 225 Honda 4 stroke and get much better fuel economy with the Honda. You just have to find the sweet spot and run it there. I use a NORTHSTAR fuel flow gauge and watch it for best running speed VS fuel consumption.