Have vibration with new prop???

[JWAT]

So I just removed the stock prop off of my '97 Super Sport and replaced it with an Acme 644. After running it for the first time today I noticed that when I took off to pull a rider up, I would get a lot of vibration that wasn't there before. I would also get it if I was cruising around 30-35 mph. The weird thing is that is doesn't do it anytime else. Once the perfect pass set in at 22 mph, it ran great with no vibration. There was also no vibration when idling. Does anyone know what would cause this? Thanks for any help.

[H2O]

RE: Have vibration with new prop???

Prop nut is loose. Retighten it.

[JWAT]

Sweet, thanks. If a loose prop nut causes that, then I'm sure that is what it is. I couldn't tighten the nut as much as I wanted because I couldn't get it to the next slot where I could stick the pin through. Should I really crank on the nut a lot so it tightens one more notch? Also, has anyone ever changed out their slotted nut for one of the nuts that just has the nylon seal on it that doesn't use the pin? If so, which type of nut do you prefer?

[NCH2oSki]

Just try turning it to the next slot, it may take some muscle to do it. I dont recomend switching to the nylock type nut, they can grab the holes in the shaft and make a mess of your driveshaft. When I installed the nylock nut it locked up after passing the holes in the shaft, and wouldnt loosen or tighten. I had to cut it off and it was not fun.

[JWAT]

I tried to tighten the nut some more today and I can't get it to turn far enough and I am really putting a lot of pressure on it. I'm pretty sure the prop is seated all the way. Is there anything else I can do? Does anyone else have any experience with the nylock type nuts?

[H2O]

Are you certain the key is fully seated and not preventing the prop from sliding up the shaft all the way? Remove prop and try again. Fully seat prop without the key and mark the shaft with a magic marker. Remove prop again and seat it with the key in place making sure the prop slides up to your mark. Tighten prop nut to 40-50 lb-ft. Then if it still vibrates the prop may have issues and a call to Acme would be in order.

[DanielC]

Go back to your stock prop, and see if the boat still vibrates. This will help you confirm if the new prop is bad. Another possible cause is prop shaft alignment. To check it is fairly easy with a direct drive, but quite involved with a V-drive. Sometimes some props will vibrate on one boat, but run fine on another boat. If you get a different castle nut, sometimes the holes will line up better with the prop shaft hole. The idea about the felt pen is a good one , also. I have had my props straightened a few times, and they got bad, even when just straightened, so I tried a different prop repair shop, and they found that the blades were straight, but not clocked correctly, causing a vibration.

[Mikeski]

Some props have a shallower keyway cut than others. If it's riding up on the key it won't center and that will cause it to vibrate. Check to see if the key is too tall. If yes you will need to file it down.