Twin 200hp HPDI RPM Split

[astrobud311]

I have a Twin 2004 HPDI's with about 400 hours one each motor. I just got this boat a little while ago, when I sea trialed it, I noticed at WOT the port motor was at 4200 RPM's and the stbd was only at 3500? The boat was running straight and smooth, no pulling to either side. The previous owner stated that he thought the throttle cable had maybe stretched out over time and had to be adjusted. My question is, does anyone have the slightest idea on what may be the problem? I know it could be almost anything, but does anyone have a suggestion on where I should start troubleshooting this split. Also 4200 RPM's seemed a little low to me at WOT, what is the recommended RPM range at WOT for these motors. I think the props are pitched at 19 so maybe I just need some new props??

[99yam40]

Sounds like you have some sick motors or you are over propped. Or probably both with the RPM difference. Check this site for a rig close to yours and see what props they used and what kind of performance the got out of the motors.
Performance Bulletin Home

You can always have the motors tested with the Yamaha test props to see if they are putting out like they should and then fix the motors if it shows they need fixing before you wipe them out

[astrobud311]

I don't think that the motors are "sick". They both start fine, run great, no smoke, no sputtering. I do think that the props are wrong but I don't think that would be causeing the RPM split. I'm just looking for a starting point for troubleshooting.

[99yam40]

1st thing to do in troubleshooting on any motor is test compression, spark, timing, and fuel pressures.
Easiest thing to do is have them tested with the test props like I said to see if motors are putting out the proper Hp and hook up to computor to see what is going on.

[astrobud311]

Any idea on how much that usually costs?

[99yam40]

call your local Yamaha shop and ask