shaft ad props

[pathfinderstu]

I bought a classic 10metre lobster type boat recently, I thought to props pitch may not be right so sent it off and they managed to correct the pitch...so. Put.it back on in dock reelaunched the boat and almost immediately Hit a large turtle with it. the gear box slipped and vibration was a lot. So limped back to the dock pontoon 50 metres off: Bear with me please....a diver took the prop off and was sent to a different local prop man who straightened and balanced it...prop put back on with boat in the water and tested....not happy with the performance speed though better than before and defineately not happy with the vibration...so have decided to buy a new prop made especially for the boat....my question is is it possible that the shaft might be bent slightly also, or am I just getting paranoid...your views will be appreciated thanks.

 

[oldgit]

I bought a classic 10metre lobster type boat recently, I thought to props pitch may not be right so sent it off and they managed to correct the pitch...so. Put.it back on in dock reelaunched the boat and almost immediately Hit a large turtle with it. the gear box slipped and vibration was a lot. So limped back to the dock pontoon 50 metres off: Bear with me please....a diver took the prop off and was sent to a different local prop man who straightened and balanced it...prop put back on with boat in the water and tested....not happy with the performance speed though better than before and definately not happy with the vibration...so have decided to buy a new prop made especially for the boat....my question is is it possible that the shaft might be bent slightly also, or am I just getting paranoid...your views will be appreciated thanks.

Being a bit of an expert on hitting things and bending prop blades and shafts (let me count the ways) find it difficult to believe that hitting something as insubstantial as a turtle would bend a piece of 1.5 inch ? stainless steel.

Need the boat out of the water and easy to set up a simple rod system or perhaps dial gauge to check for damage.

 

[omega2]

Check the r&d coupling, if ok then check the damper/drive plate.

 

[Kawasaki]

Check the r&d coupling, if ok then check the damper/drive plate.

Then, check out the Turtle
Should be easy to identify
Be some decent 'ID' marks on His /Her bimini /hard top
Then you can hand said creature a copy of the rules of the road at sea!
Mind you, you have a Lobster boat
I believe Turtles do like the odd Lobster

 

[pathfinderstu]

Being a bit of an expert on hitting things and bending prop blades and shafts (let me count the ways) find it difficult to believe that hitting something as insubstantial as a turtle would bend a piece of 1.5 inch ? stainless steel.

Need the boat out of the water and easy to set up a simple rod system or perhaps dial gauge to check for damage.

Ermm shaft 1.5inches ..prop bronze, 4 bladed, dia 25cms, pitch 20: /18.5 weight 12.7kilos.
turtle was solid 3ft x 2 at least. What I think happened was the turtle was attached to some kind of net fishing line which got caught round the prop , reeled it in then the line broke after impact. Leaving one of the blades badly bent.

B

 

[pathfinderstu]

That sounds a sensible answer thanks, is it easy to check the damper...drive plate.

 

[omega2]

That sounds a sensible answer thanks, is it easy to check the damper...drive plate.

It is sitting in the bell housing, so the r&d coupling will need to be undone then the shaft slid back, to allow the gearbox to be removed, then remove the bell housing. Hopefully there will not be any bits of broken metal therein.

 

[oldgit]

From your further info, possible you have bent a "P" bracket. ?

Been there as well..........

As the rope goes tight it yanks the bracket sideways enough to bend it an inch or so.
In my case a rope left dangling over the stern, one end still secured to bollard, went round prop.
It stalled engine. It was only on close inspection much later, that definate bend in bracket shaft was spotted.
Temp. emergency fix is to put in small wedge to realign or any decent workshop can straighten with press.

 

[Neil_Y]

Running an unbalanced prop can also wear the shaft bearings quite quickly, so that may be worth checking.

The rope around props can (and does) pull the gearbox off the engine, snapping all the bolts so that will most likely be the reason for any damage. As the rope fills the gap between prop and strut/P bracket it pulls the shaft back with considerable force. I've just got back from a marine trade show and met a guy who's prop had jammed and stalled the engine, the coupling inside the gearbox had sheered teeth and twisted the crankshaft. So sadly the rope can cause can cause damage to a number of items in the drive train. The most common is that it pulls the engine off its mounts or moves it so you need to check everything. The more hp you have the more damage.