Whistling From Prop

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Hey guys hope all is well on the water. I'm new to the site and I have been browsing around to see if anyone has already answered my question but no luck finding it yet. I have a 07 Grizzley Tracker 1860 SC powerd by a 2007 50hp Mercury EFI 4 Stroke. From the factory the prop was a Solace aluminum 11.1x14 which seemed to work good with two guys and minimal gear in the boat but since I also duck hunt out of this boat I often have alot more weight in the boat at time. Well the first problem was that when the boat was loaded down it wouldn't get up on plane very fast at all so I wasn't really happy with the performance so I ended up doing some research and decided since I needed a new prop that I would go ahead and play with prop sizes a little bit. Well I ended up buying a quicksilver black diamond aluminum 10.75 x 12 which is was all the sites recomended with the weight that I would have factored in between minimum and maximum weight I would have in my boat and they all recomended this size prop. Well I installed the prop just like my owners manual says applying 55ft/lbs of torque and adding a marine grease to the prop shaft prior to installing the prop. Took the boat out to the lake yesterday to test the prop out and it performed really well. I lost about 1mph but gained a massive amount of hole shot which is what I was looking for to begin with. The only problem i'm having is that when I engage the prop with the motor trimmed all the way down and accelerate to trolling speed approx. 2-4mph I hear a humming/whistling noise coming from the motor but when I give it gas it will quit or If I am still moving at trolling speed and trim the motor up a few inches it will quit. I'm really confused about what this could be or if this could cause any permanent damage to my motor. I was thinking that maybe I could bump it down to 50ft/lbs and add more grease to see if that would take care of it but I dont think that is my problem but I haven't tried it yet. I do know that when the old 11.1 x 14 was on it didn't make any noise. What do you guys think it is and what should I try to remedy this problem. Thanks a bunch guys for any help in the future and be safe on the water. Oh and the last thing is that i'm almost positive it is coming from the prop/propshaft becuase this noise only occurs when in gear. The noise also kinda sounds a little bit like a really quiet surpentine belt that is wore out or lose if that helps any. Ok thanks for the help guys.

 

[topdeadcenter]

Re: Whistling From Prop

Oh i'm sorry but I forgot to say that the prop is equipped with a flo-torq 1 rubber hub if that helps at all.

 

[BaileysBoat]

Re: Whistling From Prop

Does the prop spin freely by hand in neutral? Any play back and forth on the shaft? Sorry, never had a merc, but is there any chance a line thrust washer or spacer is reversed? Did the Solas come with a hub adapter, maybe the Mercury prop doesn't use some of the Solas adapters. Interesting to hear how this turns out.

 

[topdeadcenter]

Re: Whistling From Prop

Ok so the prop spins freely back and forth in neutral and there seems to be no play in the prop. The owners manual says for a flo-torq drive hub propeller to install foward thrust hub, install propeller, propeller nut retainer and propeller nut on to the shaft and then tighten propeller nut to 55ft/lbs and finished. lol sounds simple but i'm gonna go look at it right now to see if I put the forward thrust hub on the right way.

 

[steelespike]

Re: Whistling From Prop

I would suggest using a piece of hose like a stethescope and try to pinpoint
where the noise is from.The throttle setting for the same trolling speed would be different with the 12 than the 14 prop.engine speed and load would be different at the same throttle settings.perhaps this brings out some sort of vibration.

I was refering to the fact that with the 12" prop your throttle position would
be different for the same trolling speed than the 14.And perhaps that position
creates some sort of sound anomoly.
Maybe try the 14 and see if you can force it too whistle by playing with the throttle and playing with the trim.How did you establish that it is surely the prop itself?

 

[topdeadcenter]

Re: Whistling From Prop

Well i'm sure that the noise is coming from the prop but i'm not sure why or what it is. If it is the throttle setting how and where are the adjustments to fix this problem. It's weird though becuase I would think if it were vibrating then the faster I go the worse it would get but it gets better the faster I go or even when I trim my motor up at low speeds. I'm not sure what to do but I took the prop off and made sure everything was put together right and it was so beats the heck out of me but I would sure love to know what it is. I have had alot of friends buy different pitched props for there boats and not have any problems so the throttle adjustment thing is confusing me a little. Would it be to much of me to ask if you could explain this adjustment? I appreciate the help greatly