Vibration

B

buckeye

Member
Joined
Dec 30, 2002
RO Number
10928
Messages
70
Recently developed a vibration once I go above 2500 rpm's. Props were scanned and balanced recently. Other than pulling the boat any ideas of what to look for?
 
Never hurts to explain what type boat/engine/drive you are asking about.

Did you 1st notice the vibration sometime after the prop scans?
 
will it do it in neutral? This will pretty eliminate or confirm engine or input to trany
 
More details: 1985 Silverton 5.0 L crusader v drive; no vibration when rev'd in neutral. Did not notice a vibration, at least to current extent, immediately after scan.
 
A little more info, the last year the boat has not been running as we have repaired / replaced both carbs, installed electronic distributors as well as one muffler. I wouldn't think any of these items would impact vibration though.
 
Were the engine mounts disturbed to get to those mufflers? When was the last time the struts were inspected?
 
Is the vibration on both sides?
Unless you have inspected the props very recently they could be fouled. Call a diver.
 
start by inspecting the port prop. Some junk may have attached itself. First thing I do is run in reverse to see if that helps if not get a diver though he probably wont be able to tell if one prop is slightly bent.
 
Cutlass bushings?

you said the props were recently scanned. Perhaps one of the shaft nuts wasn't torqued properly?

Bob
 
And while you or he is down there, make sure any shaft, rudder and tab anodes are in place and very tight, plus check for any play at the cutlasses. Every trip runs some risk of a prop debris strike ( or maybe picking up a small line, etc. ), and they may be unnoticed at the time.
It's possible a new muffler may have different resonance characteristics at that rpm.

Is the shaft spinning smoothly in the shaft seal or stuffing box or is there and discernable wobble?
Any possibility of rudder wobble from insufficient toe-in or out?
 
Is there a specific RPM that i vibrates most? Kinda in the realm that sandy mentioned...does it feel like a sympathetic/harmonic vibration with the other prop? Kinda like when the engines harmonize.
 
wouldn't be the first prop installed with the key on the ramp.
 
A LITTLE MORE INFO. Last season Teflon shaft seals were installed in the stuffing box. I noticed that there was NO water dripping at the nut. Could that be an issue?
 
Do you feel vibration on the shaft if you put your hand on the stuffing box while it's turning? Do you see any wobble at the stuffing boxes with shafts turning? Are the stuffing boxes just warm to touch with shafts spinning at cruise rpms? Goretex (GFR) packing is virtually dripless. Certainly there should be no dripping when shaft not turning.
 
First thing to do would be to go for a swim and check the props for debris, growth, line around the hub etc. check th shaft zincs too. See if you can feel some play in the cutlass bearing, wheel nuts...

Next, make sure all looks good in the engine bay including loose mounts or couplings. Check for any sign of a wobble at the stuffing box
 
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