WOT RPM for Evinrude Jet Drive?

[nslsubject]

I have an 1995 (or so) Evinrude 90/65 hp factory installed jet drive. WOT right now for my set up (16' Lowe Roughneck, side console, two 6-gal external tanks) is about 4500 rpm. Most of the posts I've seen indicate around 5500 rpm should be normal for a 90hp. My question is this: Does the different loading of a jet drive compared to a conventional prop drive account for the difference in rpm? Or does the rpm indicate some other problem? The motor seems to run reasonably well throughout entire range of rpm.

This is a new boat for me so I don't have any history to compare the current WOT rpm to.

Thanks,

 

[ondarvr]

Re: WOT RPM for Evinrude Jet Drive?

I have the same setup. 90/60 on a 16' aluminum sled.

The WOT RPM's should be the same, at 5,500+, the motor has no idea of what's connected to the other end of the shaft. It's hard to tune a jet pump though, not many impellers are made for them, so you don't have many options. I don't have a tach on this boat, so I'm not sure if mine is correct either. Now that you bring this up, I think I'll go out and get one soon.
Thanks.