Speed at what RPM questions

[jack Stone]

I got a lot of questions at to speed at what rpm inquires during the sale of our boat.
This is from the survey the buyers were kind enough to share with me after the bought her.
I thought this might help due to the many questions about what was real speed vs RPM people asked me
when they called.

This is from a 2005 Yanmar 315 flushdeck just sold. With under 200 hours.

Yanmar recommended max rpm is 3800-3900

Our boat hit 3850 at WOT.
Surveyor said that is right where she should be.
Note: Clean bottom, just panted 5 months prior.



This is verbatim from the survey

“Using a handheld GPS surveyor recorded these speeds at rpm.

750 RPM = 3.4kts
2700 RPM = 11.7kts
3200 RPM = 18.5kts
3850 RPM = 23.6kts

1 knot = 1.2 MPH

These speeds are an average taken with and against the current”

We are in the ICWW near Wilmington NC. I’m guess the current that day was about 3 kts south.

Hope this helps with others with the speed question.

[chiefrcd]

My numbers almost exactly. 6lp300STE. Same engine as a 315, just rated at different fuel temps.

[Cape Codder]

Those numbers match pretty close to mine too, turning a 19x19 prop.