Volvo Sail drive problem

[Mirage Gecko]

I have a cat so have two of these.
One of the drives has developed what I would call a wobble.Feels and sounds like a shaft drive with a dud cutlass bearing or a rope around the prop but it's not that.
It's not constant,sort of spasmodic but there about 80% of the time does not get better or worse or increase in frequency with more revs but noticeable above 1500 revs and not really noticeable below that.I feel it thru the hull rather than thru engines which are running sweet and do not think it is engine mounts.Gearbox oil checked and good.Fixed props and it disappears when sailing only.
I am relatively new to this boat but do know props were off and new seals and zincs fitted before I purchased it 6 months ago.
Any ideas?
Chris

[belizesailor]

Confirm that prop and zinc are secure. Many have lost stock Volvo props. A loose or out of balance prop could cause this issue. You could swap on a known good prop to confirm. This is the best case scenario.

Next best case: Could be a prop shaft/bearing issue. To check, remove prop and see if prop shaft has any play to it using hand pressure (it should not). This test can be done in the water.

Other possibilities are not pretty. Any internal sail drive repairs require specialized tools, skills, parts, and $$$.

Check the sail drive leg itself to make sure there is not excessive play...it should move just a little with firm hand pressure.

Could be a gearbox/coupling issues. That's better than an internal sail drive issue. Open up the engine room and give it a test run to see if you can hear or feel an obvious problem area.

Safety note: if you are doing this in a marina then disconnect (not just turn off) all shore power and turn off inverter if equipped...you will be in the water grabbing big metal parts of the boat...bad way to discover an electrical issue.

[Mirage Gecko]

Originally Posted by belizesailor

Confirm that prop and zinc are secure. Many have lost stock Volvo props. A loose or out of balance prop could cause this issue. You could swap on a known good prop to confirm. This is the best case scenario.

Next best case: Could be a prop shaft/bearing issue. To check, remove prop and see if prop shaft has any play to it using hand pressure (it should not). This test can be done in the water.

Other possibilities are not pretty. Any internal sail drive repairs require specialized tools, skills, parts, and $$$.

Check the sail drive leg itself to make sure there is not excessive play...it should move just a little with firm hand pressure.

Could be a gearbox/coupling issues. That's better than an internal sail drive issue. Open up the engine room and give it a test run to see if you can hear or feel an obvious problem area.

Safety note: if you are doing this in a marina then disconnect (not just turn off) all shore power and turn off inverter if equipped...you will be in the water grabbing big metal parts of the boat...bad way to discover an electrical issue.

Cheers thanks for the response.
Have checked and Ok everything inside the boat so need to get somewhere I can check in the water.
Anyone know any divers Hervey or Tin Can Bay area?
Chris

[Mirage Gecko]

Originally Posted by Mirage Gecko

Cheers thanks for the response.
Have checked and Ok everything inside the boat so need to get somewhere I can check in the water.
Anyone know any divers Hervey or Tin Can Bay area?
Chris

Just been checking manuals and drawings etc and thinking because the noise is not constant or matching revs would it be possible the zinc is loose and shaking around???.Guess I need to get in the water.
Chris

[NB2013]

Also keep in mind that all sail drive props, folding or fixed have a safety hub that allows the shaft to still turn a bit if the blade come to and abrupt stop. Like when you get a lobster line tied around the prop. This allow the hub to take the forced stop without hurting the sail drive shaft and gears.

The problem is that after such and event, most will remove the line and not notice that the hub has a wobble for the severe stop.

Dive to check for hub wobble. The only way to fix it is the buy a new prop.

[jaybird1111]

One of mine used to throw its zinc regularly before I finally fixed the problem by cleaning the screw threads thoroughly/tapping. Do a Google search, I learned about it on one of the forums

[gjordan]

Since it doesnt seem to change frequency with rev change, and you feel it through the hull, I would take a look at your rudders. I am assuming that the rudders are close behind the props, and a loose bearing, or possibly a poorly repaired rudder could cause a vibration. All of the things mentioned before are possibilities, and the rudder is just one more thing to look at. Best of Luck. _____Grant.