Noise with new prop

[long_lake]

99 2100V, I replaced the OEM 4 blade prop with a 3 blade ACME prop (called ACME and got the prop they recommended) over the winter and ran it for the first time over this past weekend. When I pull the boat out of gear at any speed that I am on plane and let the boat coast to a stop I get a rather loud WHHHRRRing noise accompanied by a minor vibration for the last 3-4 seconds before the boat comes to a stop. Is this typical for this type of prop or do I have a bearing or something going out and why would it just be apparent now after I switched props?

[lee]

Is the prop nut tight?

[UNSTUCK]

Forget to put the key back on the shaft when installing the new prop?

[chpthril]

Need to make sure the prop is fully seated on the shaft and a tight nut is not always an indication.

[NICKYPOO]

Not too tight though. I think it's only 35lbs. DQMOT but check the install directions. Did you lube the shaft before putting the new prop on?

[long_lake]

Thanks for the feedback I will definitely check the prop nut tonight. I didn’t have a prop puller and the old prop wasn’t coming off without one so I took it in to have it installed. I had assumed they installed and tightened it correctly but that may not be a good assumption.

[IDBoating]

The whirring sound could be the prop and transmission free-wheeling once you take it out of gear. If you were on plane, there's a lot of force on the prop while the boat is slowing down. I've driven around with the transmission exposed at times and can assure you the propshaft keeps spinning after you take it out of gear if the hull is moving at anything over a slow drift.

Sorry to say, my first thought was "When they removed the old prop, they beat on it so hard they damaged the transmission". I hope that's not true, but I've seen people reach for the sledgehammer when the prop puller didn't pop the prop right off first thing. I yell when I see someone preparing to do that, but who knows what they did in the shop when nobody was watching.

If it isn't a missing prop key or some other prop mounting issue, experiment with slowing down while still in gear (i.e. back off the throttle while still keeping the transmission engaged). See if you can narrow down the circumstances under which it occurs.

[long_lake]

I just checked my prop shaft nut & key and it appears to be installed and tightened properly.

I did spin the prop around by hand and noticed a couple of things; it doesn’t spin really freely (not sure if it is supposed to), and there is a noise which appears to be coming from between the shaft and prop shaft strut. Can’t say for sure if it’s the same noise I am hearing while coasting to a stop.

[chpthril]

Just to reiterate, a tight nut does not indicate the prop is fully seated on the tapered shaft.

Yes, its normal for the prop to be hard to turn and not free wheel

The cutlass is water lubed, so a squeak while turning could be normal.

[long_lake]

Point taken, I will verify the prop is fully seated, thanks for the feedback. I guess my next step is to track down a prop puller and put my old prop on to see if it is related to the prop or if something is now damaged. Thanks for all of the replies.

[IDBoating]

To clarify a bit: When the transmission is out of gear, the prop should be "stiff" to turn but still possible with one or (at most) both bare hands. When the boat is moving and out of gear, it's normal to see the prop spin due to the water that is passing through it... the force is sufficient to overcome the internal friction that you feel when you turn the propshaft by hand on the trailer.

I can turn my propshaft with one hand by spinning the fitting on the front of the v-drive. I can't spin it hard and have it "coast to a stop", but one hand it all that's needed to turn it. That should give you an idea of the force required.

[Smcqueen]

As far as prop noise, I replaced the prop on my '14 Z3 with an ACME prop, the new prop is definitely "noisier" than my stock prop. Possibly due to the tool marks on the blades from the CNC machining process. My prop "sings" at low speed, and when I drop throttle quickly I will get the heavy whirring sound. Baumann's Prop service here in Houston will clean up and tune the prop, I have been just waiting to see if I bend it first before I spend the money.

[chpthril]

Possibly due to the tool marks on the blades from the CNC machining process

This would be plausible, except your "stock" prop as also an ACME, machined in the same manor.

I would also hesitate to send a brand new prop to a prop shop for tuning and cleaning if a problem with its machining is suspected. Get back with the manufacturer.

[long_lake]

Thanks again for all of the responses, it is all very helpful. Thanks for the clarification on the prop spinning IDBoating as that is very similar to the way mine spins as well. I am also glad to hear someone else noticed a different noise with a change in props that is similar to what I am hearing.

I called my shop and they claim their “prop specialist” is the only one who works on inboard props and he swapped out the prop on my boat. I think I will still put my old prop back on and see if the noise follows the prop.