Rope Cutter Causing Prop Shaft Wear?

[Neo]

There was zero movement of the prop shaft (circa 1987) in the cutlass bearing when it was inspected.



When the shaft was decoupled from the transmission and slid aft, grooving from the cutlass bearing was clearly evident.



Is this normal wear? The grooving is hard to see but is easily felt.

Did the installation of the rope cutter restrict the flow of water through the cutlass bearing, thereby causing excessive wear? Maybe crud accumulated in the bearing because of low water flow, which caused wear?

Or was the cutlass bearing too tight?

[Lancerbye]

My guess would be that the restricted water movement through the cutlass bearing caused the problem. The bearing needs water flowing through it and around the shaft to provide flushing and lubrication. With out a good flow through, stuff like sand and shells can accumalate causing the bearing to get packed with debris, heating and scoring would be the most likely result.
Years ago when I owned a commercial fishing troller and did my own maintenance, an experienced shipwright told me to be carefull while installing the donut style zincs on the shaft behind the keel, which had the cutlass bearing. He told me if it was too close against the bearing, the bearing would starve for water and what you see on your shaft would result.

[Neo]

I'll be sure to flush out the bearing before installing the prop, and the rope cutter will be eighty-sixed.

I assume that as long as prop is snug in the bearing, I needn't worry about the wear??

[Nicholson58]

Originally Posted by Lancerbye

My guess would be that the restricted water movement through the cutlass bearing caused the problem. The bearing needs water flowing through it and around the shaft to provide flushing and lubrication. With out a good flow through, stuff like sand and shells can accumalate causing the bearing to get packed with debris, heating and scoring would be the most likely result.
Years ago when I owned a commercial fishing troller and did my own maintenance, an experienced shipwright told me to be carefull while installing the donut style zincs on the shaft behind the keel, which had the cutlass bearing. He told me if it was too close against the bearing, the bearing would starve for water and what you see on your shaft would result.

I agree on the restricted flow. Ours sat for a few years before we bought from the PO. I should have disassembled. The grooves in the cutlass were full of calcium marine growth. It was like a sander grinding up the shaft. The water is suppolsed to flow through. As long as you have the shaft part out, pull it the rest of the way and inspect.

[Pete the Cat]

I have the same cutter on my boat. The installation instructions said to leave 3/4 inch between the cutless and the cutter to allow for water flow. I have not had a problem with my cutless bearing with the cutter installed. I like my cutter it gets deployed a couple times a season here in Maine despite my best attempts to avoid the lobster pots. You probably do not want to come to Maine without one as sometimes the pots are submerged and it is just not possible to avoid them. And the water is cold.

[Nicholson58]

calcuim crud in my cutlas & wrecked shaft. The shaft is in the spray-weld shop for re-build.

If you don't have circulation through the cutlas you may have a calcium build-up. Its like grinding media.

[Neo]

Originally Posted by Nicholson58

I agree on the restricted flow. Ours sat for a few years before we bought from the PO. I should have disassembled. The grooves in the cutlass were full of calcium marine growth. It was like a sander grinding up the shaft. The water is suppolsed to flow through. As long as you have the shaft part out, pull it the rest of the way and inspect.

Good idea. We hadn't considered removing the shaft, but it will give us the chance to clean and inspect the stuffing box and cutlass.

Besides, it will be necessary for us to slide the coupler up the shaft when we do the shaft alignment. As it is now, a short length of shaft sticks out from the coupler, so we can't mate the two metal plates together and measure the gap. Someone did this to "shorten" the prop shaft to accommodate a flexible coupling.



We would like to keep the flexible coupler but keep the shaft from extending beyond the metal coupler.

How much clearance do we need between the prop and the rudder? The boat is a Pearson 31-2.

[Neo]

Originally Posted by Pete the Cat

I have the same cutter on my boat. The installation instructions said to leave 3/4 inch between the cutless and the cutter to allow for water flow. I have not had a problem with my cutless bearing with the cutter installed. I like my cutter it gets deployed a couple times a season here in Maine despite my best attempts to avoid the lobster pots. You probably do not want to come to Maine without one as sometimes the pots are submerged and it is just not possible to avoid them. And the water is cold.

The boat lived in Maine for the first 25 years of its life, but there are almost as many lobster pots here in its new home, Massachusetts. I'll leave the cutter on the shelf for now, and revisit it if circumstance dictates.

[Neo]

Prop clearance from GordMay, study hall.