WOT RPM lower?

[bronxlatetour]

I have a 1990 Sea Ray 250DA with the 7.4 Bravo. The engine has been running outstanding since replacing my fuel pump. The engine used to max out at 4400RPM and between aprox. 36-39 MPH depending on how smooth the water was. That was with two people on board. Yesterday I was out with 6 large adults and 4 small kids, packed cooler, beach gear and a full tank of 100 gallons. The boat would only pull 4100 RPM. I'm vew to boating and wanted to know if it an engine issue or does weight have an effect on max RPM's? I can understand the slower speed of 33 MPH. I have the Mirage 17P stainless prop on it that I think is standard. Thanks.

 

[QC]

Re: WOT RPM lower?

Those numbers seem consistent with the increased load to me. Yes, speed and RPM will both drop or rise together with load changes. My boat varies 400 RPM and 7 MPH depending on load . . . With that said, there could in fact be something wrong with your boat although I don't think so. The proof will be in your performance numbers when you revert to a more typical load.

 

[freddyray21]

Re: WOT RPM lower?

my boat does the same under a load. Nothing to worry about in my humble opinion

 

[bronxlatetour]

Re: WOT RPM lower?

Thanks for your opinions. I feel a little better now. I'll know for sure tomorrow, I'm going out with just one other person.

 

[cmyers_uk]

Re: WOT RPM lower?

How I look at it is if you go up a steep hill in a car in high gear you can only pull say 3000 rpm with you foot flat on the floor. But on the flat you can get 4500 rpm. In a boat its no different heavy boat sits lower in the water = more drag (like being on an incline). You may find that by trimming your engine up to get as much of the boat out of the water you can get closer to the max rpms.

 

[bronxlatetour]

Re: WOT RPM lower?

Thanks to everyone. I went out today and the boat pulled 4400 RPM again with three people aboard.