Vibration on left prop Carver 455 aft cabin

[Seanflanman]

Hi,
I am a new owner of a 1997 Carver 455 aft cabin. During the survey, we noticed the left prop nut was loose and was tightened onsite by a the marine shop. The owner of the marine shop said they were the ones that completed some work on the boat recently and sent the props out and tightened the nuts at that time so they were surprised to see it loose. The boat did not have a vibration on water during the survey. A short time later, we noticed a vibration on the left side and I’m assuming I need to change the prop nut kit? Any thoughts or help would be appreciated. Thank you!!

[bud37]

Welcome to the forum.......ask your marine shop owner how they fitted/lapped the props on, or if they just stuck them on and tightened........what order are the nuts on small next to the prop or big next to the prop.

Redone props need to be fitted/lapped to the shaft and the key fitted properly or there can be problems.

[Viper]

Welcome aboard. A little history about the work the marina did to the running gear and why would help. Was it just to tune the prop or was an impact involved? If an impact, was the shaft dialed properly? If it was bent, did they replace with new or straighten it. A straightened shaft can revert back to its bent state over time and cause a vibration. The vibration can loosen the prop nuts.

There is a process to installing a prop correctly. As Bud mentioned, the fit between the prop and shaft mating surfaces must be checked and lapped to ensure the two mate properly. That also applies to the key/keyway. Any slop here will result in movement and ware over time. The seemingly simple act of installing the prop nuts is more involved than one may think. As mentioned, the smaller jam nut should be up against the prop with the bigger nut going on last. The caveat here though is that the small/jam nut is not meant to "tighten" the prop on. You first tighten the prop on with the large nut, then remove the nut, install and tighten the small/jam nut, then install and tighten the large nut to the small nut. Because the threads of the jam nut get slightly distorted as they are designed to do and is what helps keep the assembly in place, it's always a good idea to replace at least the jam nut after prop removal. Nuts right?! This is the proper way to install a prop so it doesn't loosen off under load on its own without any other negative outside influences.

Were the strut bearings checked, and are the struts properly aligned? Was an engine alignment checked/done, and how soon after the boat was launched did they do the alignment? The hull should rest in the water for a day or two before a final alignment is done or the alignment can change soon after.

Also keep in mind that you shouldn't rule out other causes like having hit something on your initial survey outing. Under the right conditions, hitting a log for example isn't always noticeable from the helm. It doesn't take much of a tweak on one of the prop blades to create a vibration. Conditions may also have differed from one run to the other. The problem may have existed in the first run but not surfaced if the conditions weren't right, then noticed on the later run. It could have been the result of or changes in water conditions, rpm, weeds, etc. There are numerous things that can cause a vibration, heck even a poor running engine can cause that.

Keep us posted.

[waybomb]

Welcome aboard!

[pepmyster]

Welcome, following this post.

[Seanflanman]

Thank you all for your replies! I will talk with the shop and ask about the lapping of the prop. The smaller nut is furthest to the rear right now and the larger is next to the prop? Hoping this picture shows. Sounds like this could be the problem? Thanks everyone!

[Viper]

It's not quite clear but from what I can see in that pic, you might want to have them take a closer look at that strut bearing. Looks to me like there might be chunks missing. Also, can't tell if it's marine growth or not but there seems to be rust and pitting on the strut, prop, and rudder. I'd check and ensure the bonding system wiring is intact and in good condition on all those items. I don't see a shaft anode, are there anodes anywhere else?