Cruising RPMs from 7.4L

[QC]

Re: Cruising RPMs from 7.4L

Hey Doc. Post your RPM at WOT (full speed) too. This will tell us if the propellers are sized right and/or indicate engine condition. Based on your speed I think she is perfect, but it's a good piece of data for you to have.

 

[Mischief Managed]

Re: Cruising RPMs from 7.4L

My 7.4 MPI/Bravo 3 equipped boat will plane at 2800 RPM with a full load and tabs retracted, and 2500 RPM with a full load and the tabs all the way down. However, it gets much better fuel mileage at 3000 to 3400 RPM. I can run over 4000 RPM and STILL get better fuel mileage than I get at 2500 RPM.

My experience with a fuel flow meter throughout last season was an eye opener. My boat is much more efficient "solidly on plane" than it is "barely on plane".

 

[Doc_Vegas]

Re: Cruising RPMs from 7.4L

Hey Doc. Post your RPM at WOT (full speed) too. This will tell us if the propellers are sized right and/or indicate engine condition. Based on your speed I think she is perfect, but it's a good piece of data for you to have.

I think the RPMs were limited to about 4500. It seemed that all I could get, maybe a touch more. It did not seem like a power limitation, but perhaps a cable or other "restrictive" limitation.

 

[QC]

Re: Cruising RPMs from 7.4L

I think that it is perfect. It is in effect a power limitation, but where it should happen, the engine has to run out of power to make her go faster somewhere if not they'd sell one engine for all applications . . . Basically you want your propellers and boat and engine power combination to result in a max RPM between 4200 and 4600 on your 7.4 MPI. 4500 indicates that the propeller pitch matches your boat and engine combination properly, allows it to make peak power and will result in the best economy and performance and durability compromise. I'd say you are pretty much dead on. Your top speed tells me she is running right, and the RPM tells me she is propped right. Don't step on any sidewalk cracks and stay out of the Casinos as your luck is all used up . . .