Engine is racing

[rrobbiep]

I have a '98 Nautique that I bought this season and am learning as I go thanks to this forum.

I've learned othat the white smoke coming out of the back when I pull a skier out of the water is steam not smoke. I guess I shouldn't worry about then, but I have another problem.

Periodically (if not often) when I pull the throttle back after pulling a skier the engine will "race" at about 2000-2500 rpm's in neutral and will not slow down unless I turn the engine off. When I start it back up it idles fine. The performance is great... except when I slow down again an pull the throttle back in neutral. It is less likely to do it the slower you pull the throttle back. There have been two occassions, as well, while pulling a skier the boat will let out a loud "scream". At such time, I but the boat in neutral... start it back up and it runs fine.

I gave the boat to my mechanic a few weeks ago and described the symptoms... He checked it out and said the boat runs great and coudn't find anything wrong. (I am obviuosly losing faith in him).

I'm a newbie, so any advise as to what the problem may be would be greatful.

[NCH2oSki]

Is your boat equiped with Perfect pass?

[rrobbiep]

It does not have perfect pass.

[rrobbiep]

Update: Just took the boat out again for a workout... when I get it going over 25 mph there is a consistent "wining" sound... then occassionally a loud "scream". Both go away when I pull the throttle back an cruise at 15-20 mph.

[crotchrocket]

First of all is it Fuel injected or Carbed? If fuel injected I would look at the Idle Speed Control. Might be sticking open. You might have to replace it. Or if you are lucky you can clean the valve up. These go bad often on Cars so it would not suprise me. If its Carbed then I would check to make sure you secondaries are not sticking open. Sometimes they get a little moister in the rods that hold the butterflies and they stick open. Might have to take the base plate off and take it apart, clean and lub with light oil and reinstall. That would be my two guesses to your problem. Ofcourse if its Fuel injected might just be the Throttle body sticking open. Just clean it really well.

[rrobbiep]

It's carburated, so I'll try your suggestion this evening. I'll let you know.

Thanks!

[Laptom]

Is the screaming noise something like reving the engine and not the speed? In that way it's possible that you're transmission fluid is low (check when transmission is warm).

[rrobbiep]

The "screaming" does definitely not sound like a revving of the engine. It's a scream. It's loud and it's scary. Those who have heard it say it sounds like a belt issue.

I had a friend look at it last night. The carburator is definitely dirty (alot of carbon), and we notice alot of black residue that looked like it came from the alternator belt (?). He suggested replacing the belts too b/c they may be slipping and causing the screaming. Any thoughts?

[TwinTip]

Take a look at the belt. Since you will be doing this with the engine box open and while the engine is running, be very careful with any body parts, hair or clothing. You don't want anything to be caught in the belt causing an accident.

As you accelerate (you can accelerate slightly while disengaging the transmission, be careful though and don't do this at high rpm's), if any parts of the belt that are not touching a pulley seem to move up/down (or left/right), this might cause the squeaking. When at low rpm's, you will probably not see the "flapping" or bouncing of the belt, however, as you increase rpm's and start hearing the noise, you will notice that this oscillation is probably becoming greater and greater, causing the squeaking noise. The higher you go on the rpm's, the greater the amount of flapping or oscillations and the higher the noise. You might reach a point where the rpm's are high enough that the flapping on the belt will be reduced so much that the squeaking is no longer present.

I had a similar problem and the squeaking came from the belt. It was tight enough to work yet lose enough for the squeaking to take place. I replaced the belt and it is now tighter than the previous one. I have no squeaking and the engine is running perfectly.

I am not familiar with your engine and if you have a belt tensioner or not. If you don't, be careful not to overtighten the belt.

As far as your engine staying at 2500 rpm's once you put the throttle in neutral, have you checked the throttle body and made sure that it is not getting stuck midway and goes back to idle? You may be shifting to neutral but the spring on the throttle body might not be setting the rpm's back to idle. Does your throttle shift smoothly between neutral/forward and neutral/reverse or is it hard?