250 VMAX RPM Issues

I am having RPM isues w/ my 07' 250 on a Z21. I cannot get the RPM's past 5500, changed the prop 25M, 23M and it still cannot get past 5500. I have a 21M coming so I can completely rule out a prop issue. I am in Colorado so the high altitude requires a lower pitch here. I have heard it could be some clogging of a filter in the VST tank... Anyway, I want to troubleshoot before I have to pay someone to do it. It has been plugged in for a diagnostic and it reached 5900 RPM very early on. Motor has 43 or so hrs on it. Any advice will be appreciated, thanks.

Do you have a jackplate? If so, does it help to move it up or down?
Have you had the compression checked? Are these rpms with a loaded boat? Have you tried it light - just you? We might be able to get a better idea with some more info.

Yes on the jackplate, it really does not help moving up or down. I was able to get the RPMs up moving the plate up but the boat did not perform. So I can get it to spin above 5500, just not with the load of the boat as well as reaching top speed. 5500 RPM with just me or with a tourney load. No bogging sound, does not sputter, just won't go past 5500 RPM. I bought this boat from a freind and it was his Pro boat, he was able to get WOT just after breakin but has not been able to after that. I think he is more expereinced driving the boat than I am and if he cannot do it then I am not sure what I can do different.

Forgot, yes on the compression test and no codes on the computer

That sounds a lot like 300 only it was about 4800 to 5000 rpm's.. http://www.bassboatcentral.com/smileys/crying.gif

Another possibility is to have the Throttle Position Sensor checked. Have the mechanic adjust the voltage down a little just to see. Typically in high elevation you want to run the motor a little leaner than normal to compensate for the thin air. Maybe a stretch....but worth a try.
If that doesn't work....there's always a Phase Kit! http://www.bassboatcentral.com/smileys/wink.gif http://www.bassboatcentral.com/boardstuff2/beers.gif

What's a phase kit?

Nevermind, I looked it up. Thanks for your input. I'll let you know if it works or not.

sent you an IM with the website. And some info.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ckjmack &raquo;</TD></TR><TR><TD CLASS="quote">I am having RPM isues w/ my 07' 250 on a Z21. I cannot get the RPM's past 5500, changed the prop 25M, 23M and it still cannot get past 5500. I have a 21M coming so I can completely rule out a prop issue. I am in Colorado so the high altitude requires a lower pitch here. I have heard it could be some clogging of a filter in the VST tank... Anyway, I want to troubleshoot before I have to pay someone to do it. It has been plugged in for a diagnostic and it reached 5900 RPM very early on. Motor has 43 or so hrs on it. Any advice will be appreciated, thanks.</TD></TR></TABLE>

My problem turns out to be the micro switch that tells the motor to swtich from 4 cylinders to 6. It is the small switch where the shift cable connects to the motor.
I understand that this is becomming an issure with Yamahas...

That's interesting. I have to believe that at 5500 RPM I am hitting 6 cyl. I am going to put a 21P on, if I hit the limiter then I know its a mechanical issue like a clogged filter or something related to the fuel system.