Whistling Noise

[kylake33]

I have a 1998 SNOB (GT-40, 1.23:1) that has a whistling sound between 2,000 and 3,100 RPM. It is loudest around 2,600 RPM. Running at the same RPM out of gear there is no sound. When I open the motor cover the sound is more prevalent. I took off the flame arrester, ran it, and the sound was still there. There was a discussion thread a while back about a similar sound, but the cause was never specifically identified, nor a remedy mentioned. If it is the tranny, is there a fix? What other possibilities could cause the whistle? Should I rule out the prop since the sound is louder with the motor cover lifted? Thanks.

[78LS2]

RE: Whistling Noise

"Running at the same RPM out of gear there is no sound" what do you mean here?

Also, if it is the gear, put your head by the back of the box, even with it closed, and run through the RPM range. If it is making noise, you will hear it. It is more a whine, than a whistle.
If that is the case, there really isn't a "fix" as it is usually the gear teeth engaging slightly off. Meaning, the tooth of one gear is not exactly lining up with the slot on the other. Or, the teeth themselves were cut incorrectly. However, if that was the case you'd have had the issue from day one.

[kylake33]

"Running at the same RPM out of gear there is no sound" what do you mean here?

I press in the button at the base of the throttle to disengage the transmission so you can rev the engine without going forward. While doing this the sound is not present.

In general I guess the sound is sort of a cross between a whistle and a whine.

[78LS2]

oh, I follow now. sorry.

yeah, if it does not make the noise out of gear, but does in gear, I'd say your gear/transmission is whining. Did it just start to make this noise? when was the trans oil last changed?

[Johnsongc]

You may also have a cupping issue with you prop. I had a harmonic (could also be described as a whistle) sound at certain rpms on my 2001 Ski when I had a dinged prop sent back from repair. Changed props sound was gone. Just a thought.

[TRBenj]

yeah, if it does not make the noise out of gear, but does in gear, I'd say your gear/transmission is whining.

While thats possible, I wouldnt rule out anything just yet. The motor will behave very differently when it is under load vs. in neutral.

[78LS2]

yeah, if it does not make the noise out of gear, but does in gear, I'd say your gear/transmission is whining.

While thats possible, I wouldnt rule out anything just yet. The motor will behave very differently when it is under load vs. in neutral.

While I agree, I used to work in the inboard transmission industry. More times than not, the whine/whistle is the gear box.


Again, test it out with your head behind the motor box, close to the floor (right outside where the trans is). have someone run the engine up through the RPM range in gear. If it is the gear, you'll hear it for sure.

[kylake33]

I just got back from the lake, and to better describe the noise it is more of a whirring sound. I will try listening right behind the motor box, but the noise is loud enough that it I might not be able to pinpoint it. But maybe it will sound louder back there.

The sound was there when I bought the boat two years ago, and while it is not aggravatingly loud, I wish I just heard the deep sound of the engine rather than the whirring noise.

The previous owner did have the prop repaired from some small damage, so that could be it. I may buy a new prop any way and use my current one as a back up.

Other than this one minor issue I love the boat! Thanks for the input.

[mf01]

Is it the PCM tranny? Mine makes sort of a whirring noise, its a 94. Before I bought mine I test drove a 93 and it also made a whirring noise. I heard it was from the 1.23:1 tranny.

[kylake33]

Yes, it is a PCM tranny. I may have to just live with it, but that is OK since it is not that distracting and sometimes I forget its there in the background. Thanks for your suggestions.