tophatyachts.com

Greetings

I find that since a rebuild and incorrect installation;where I ran the engine out of line for about 10 minutes before the shake rattle and roll loosened the mounting bolts and chewed up the sure-seal gland.
Now correctly aligned I find that over 2200 revs a grinding noise comes from somewhere outside of the new sure seal.

My questions are;

Is this a threatening noise or will what ever it is that is grinding eventually go away?

And is there a clearance that I can measure between the prop and the cutlass bearing?

thanks

tom

Tom, I have no idea about grinding noises and cutlass bearings but I can tell ya this for certain. On those dark and gloomy nights on the muddy Fitzroy River where ya spotlight goes nowhere and ya can't see nuthin and ya could be on another planet it's so eerie and then the grinding starts, that's a bad sign. Crocs grinding their jaws to sharpen their teeth. Best to stay below decks and avoid peering out of ya windows 'cause ya can't seen nuthin anyway and them crocs will see there's food on board.

Yup, them grinding noises are bad news. Methinks the grinding in ya bearing could be bad news too. Stray bit of metal in there somewhere maybe?

All the best with ya repairs and I hope ya get some sensible replies after my useless one : ).

I had to have a cutlass bearing replaced few years back and yes it made a grinding noise, but there is no guarantee that you have the same problem. The only good news is that it was not too expensive. I think you might have to haul her out to check what is going in. I presume the prop is clean and true?

I would make an uneducated guess that the prop is hitting on the rear of the cutlass bearing housing.

All the thrust that the prop gives you is taken on the shaft, through the gearbox to a thrust bearing, into the engine block and through the engine mounts. If you remove the engine mounts and reved the engine the boat would stand still and the engine would proceed through the cabin. The engine mounts being rubber will flex enough for the prop to hit the cutlass bearing.

How much clearance have you got between the prop and the cutlass bearing? Is that what you are asking? You may be able to pinch a bit if you release the shaft coupling inside the boat and slide the propshaft backwards a few millimeters and see if it still does it at 2200 rpm. Check the movement in the engine mounts.
The coupling bolts on the shaft should be "spotted" or partly drilled so the point of the screws dig right into the shaft. If not the slightest movement in the screws allows the shaft to rotate or slide inside the coupling. Worst case, and it hapenend on a friends boat, when you put into reverse the shaft pulls out of the coupling.

For what its worth.

Tom this might help.

Greg, that diagram is a beauty! Very interesting.

Thanks Louis, I might take up illustrating childrens books, "Thomas the Top Hat and Friends"

I come from an engineering background. Did you hear about the two engineers that met in the street. Neither of them had a pencil, so they walked away in silence.

Your comments about crocs grinding their teeth makes the idea of cruising the Fitzroy R VERY appealling...not! Is it really that bad?

Dolphin wrote:Thanks Louis, I might take up illustrating childrens books, "Thomas the Top Hat and Friends"

I come from an engineering background. Did you hear about the two engineers that met in the street. Neither of them had a pencil, so they walked away in silence.

Your comments about crocs grinding their teeth makes the idea of cruising the Fitzroy R VERY appealling...not! Is it really that bad?

haha, that's very good

People regularly see crocs in the river. I have not. Nobody has been eaten. Been some close encounters but no loss of limb or anything. I am extremely careful. At night in summer down the river, people hear the crocs growling. [Tom, sorry for the hijack]

Sorry Tom to get off the topic. I hate that myself.
Did that help? You should see the area where the cutlass bearing has been hit by the prop. But I guess the water is a bit cold to just drop over the side! You could try and measure the deflection in the mounts under load and no load and measure the clearance from the prop to the bearing to confirm the interference.
Do you think the shaft has slid into the coupling over time?

Here is Felicite's prop before antifouling showing the clearance which is less than an inch.