Big Vibration when engine put in reverse

[Craig]

Guys,
Just before Christmas, when engaging reverse gear to reverse into my berth, there was a big vibration and loss of most power. This vibration occurred as soon as reverse was engaged and there was only minimal reverse trust obtained. The problem continued until the gear was put back into neutral.After the boat was tied up, I moved the throttle through the gears and could not duplicate the problem.
I've checked the gear box oil and the engine mounts and they seem OK. I do have a 3 blade folding prop on my S130 saildrive on a D1-30 engine in my 2010 Bav 38.
I'm suspecting that the clutch may have been slipping or the blades on the prop were not properly deployed but not sure how this could only happen once. Is this an indication that the clutch is wearing out??

As the problem has not repeated itself, I am having difficulty in diagnosing the issue. I'm concerned that if this issue reoccurs in strong winds, the loss of control may mean I end up on one of my neighbour's boats.
Craig
"Shirley Valentine"
Gold Coast
Australia

[dawntreader]

When a similar incidence almost exactly like this happened to me previously I went underneath (I'm a scuba diver) and found the remains of a large plastic bag around the prop and saildrive. This may explain your situation too?

[Salty]

Sounds like you might have picked up a piece of rope which dropped off once you engaged neutral. A couple of years ago I picked up a fishermans marker buoy and the rope attached to it got wrapped around the prop. Over here in the UK these markers are often very small and extremeley difficult to see in anything other than a dead flat calm. Anyway, the vibration it caused was heavy and very noticeable. By going astern I managed to unwind the rope and the whole lot floated to the surface where I was able to grab it with the boat hook and dispose of the rope and marker into the rubbish skip later on. Perhaps you or one of your mates could dive down and take a look at the prop just to be sure it is clear and undamaged. I've got an underwater camera on a long pole for this job, but with our high tides I've also the opportunity to dry out for a below the waterline inspection (I was going to say bottom inspection, but I didn't want anyone getting wrong ideas)!!!

[Boatname]

Something like this:

http://www.ebay.co.uk/itm/5M-7MM-Android-Endoscope-Inspection-Borescope-LED-Tube-Snake-Video-Camera/142402261902?epid=937848175&hash=item2127d6138e:g:zLUAAOSwX9FZMVD5

allows you to do something like this:

https://youtu.be/UDt_y0WxOzIs

[Craig]

Thanks for the input.
You may be correct about a prop wrap, although it happened in a canal that has very little debris and no fishing.
I like the endoscope camera as the canal where my pontoon is, has a large population of Bull Sharks. Impossible to dive. No one is game to swim in the Gold Coast canals.
Craig
"Shirley Valentine"
Gold Coast
Australia

[dawntreader]

I have a low-cost sports action camera with waterproof housing that I can attach to an extendable pole. As well as underwater filming of dolphins close to the bow it is also useful in port. This is the second time I've picked up debris on the prop coming out of Lorient, Brittany in France (see attached -taken in port, Cameret-sur-Mer).

[s/y Susanne]

Craig

It really does have all the hallmarks of a  temporary prop-wrap from a plastic bag. I have  a Brunton Autoprop and would say that snaring a polythene bag with one or more of the blades is the only real downside of this great prop.

Because the blade in your prop may set "hydro-dynamically" the imbalance created with only one or two blades in fully deployed mode, and the other blade mis-set is enormous, and enough to make your whole boat shiver under power.

Often just ticking over in the opposite thrust is enough to solve the issue but sadly sometimes diving to release the foul plastic is the only answer.


Mind those sharks!