Whistling from engine and certain rpms

[ktmrider1]

I get a whistling sound from the engine while at certain RPMs. The pitch gets slightly higher or lower along with the rpms but goes away if I adjust the throttle. Has anyone else experienced this? What can I do to make it go away?

I've got a 2000 21V with the black scorpion package 330hp engine.

[Kimmer322]

Do you use the boat often? I was told it if you don't use it that often the alternater makes this noise until it charges up again. I had this problem last weekend - when the guy that bought my boat came to pick it up. I was taking it out for a final ride and heard this whistling I have never heard before. Freaked me out, didn't want to give the guy a boat that had a problem. And of course it was a problem I had never heard before.

I called my boat guru and he told me the above. Mine whistled at around 1100rms and stopped when I went above that.

When the guy picked up the boat an hour later the whistle was significantly less. Also it could be the belts whining.

[mtnsmith]

I'm not sure how your sunpad to transom area is, but if saltwater is dripping off the bottom of your sunpad onto the "front" of the engine, since it is essentially backwards in the boat, then you will get corrosion on the pulleys and toast an alt pretty quick, as I did. I made a gutter to catch the water and divert it away from the accessories on the engine. I'll take a couple pics when I get home so you can see what I mean. Also, my dealer that I've given you the phone number of here in Largo has come up with a set of grounding wires to hopefully help prolong the life of the steering cable. I can take shots of those too if you would like. Or you can give him a call and he cal tell you exactly how to make a set.

[R&T Babich]

I get a whistling sound from the engine while at certain RPMs. The pitch gets slightly higher or lower along with the rpms but goes away if I adjust the throttle. ...

It sounds like you might have a vacuum leak. Your engine is the same year as ours. There is a vacuum line that goes down to the fuel pump pressure regulator that could have come off. The only other vacuum hose I remember is for the PCV valve.

It could be the drive belt or a bearing. Remove the drive belt to check the alternator and cooling water pump bearings. Put your spare drive belt on.