Is something wrong with my throttle cable????

Riverteeth · 07-07-2009, 10:42 AM

Question for the crowd: I have a 1995 200hp Yamaha jet. Got it used a year ago with my sled. Been running fine, and still does. Took it out this weekend, but couldn't get the RPMs above 4,700 (I never run it above 5,000, so I'm not missing much). Normally, I top out at 5,000, and if I wanted to run it higher I could (but I don't because of specs).

Did I bang the cable somehow on the throttle (when I was doing some work underneath with other wires), and that caused it to "pull short"? Any ideas why it won't go higher?

Orca · 07-07-2009, 11:02 AM

Did you happen to be at a significantly higher altitude? Bent or dinged prop?

Riverteeth · 07-07-2009, 01:06 PM

Its a jet, so no prop issues.

But I was at a much higher altitude: Wallowa Lake, which is 4,300 feet. I live at less than 1,000 above sea level.

So how does altitude change things?

MattPark · 07-07-2009, 01:27 PM

The higher you go in elevation the less dense the air is. Less dense=less oxygen=less power.

Check to make sure you are getting full throttle.

tbone65 · 07-08-2009, 03:40 PM

2.5-3.0 percent of your horsepower is lost per 1000 feet of elevation, so your 200 at 4300 feet is more like a 175 or so.

Granted, you may have other issues, but losing 300 rpms at 4300 feet does not seem out of the norm based on my experience.

namu mac · 07-08-2009, 03:46 PM

Do you have rock dings on the edge of the impellor? That can cause rpm drop. If so get the file out.