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Date: 25 May 2015. Inexpensive Line Cutter.

© janice142

Richard on M/V Dauntless posted to his website [https://dauntlessatsea.wordpress.com/] about the niftiest item, and I want one. All of us on boats without line-cutters on our shafts worry that the rope from a crab trap will ensnarl our propeller. That is bad. It can be very bad if the rope manages to loosen the shaft from the coupler at the transmission.

A coupler is a piece of metal that holds the shaft to the transmission so when the boat is in gear the shaft will turn. The problem develops when a line gets caught in the propeller. It can exert force and potentially dislodge the shaft from the transmission.

Basically the line can pull the shaft out from the transmission. Were that to happen the boat will not move. Water could also come into the boat and that's not good either! Worse case scenario, the boat might sink.


The Coupler, Keyway and Key plus Zincs



The stainless COUPLER connects the aft end of the transmission to the shaft. It either slides on (one piece) or is a "split ring" meaning there are two portions that bolt together around the shaft.

Next, moving toward the back of the boat is a blue arrow. That points to the KEY. The Key is a square piece of stainless (or bronze) and it fits into the Keyway. Aboard Seaweed, my key is 3.25" long and 5/16" square. I buy mine at Midwest Steel and Aluminum company 763-582-1925.

All that is just fancy Boat Talk. A keyway is simply a slot the square key fits into. It locks the coupler and the shaft together so they spin at the same time. There is a notch in the coupler and an equally deep one in the shaft. The key fits in that slot.

Aft of there are two ZINCS. Zincs are used to protect the metal in the boat from stray current (electricity). It's a part of the bonding system, which is not the focus of this article. We shall cover that later.

Water conducts electricity and zincs protect against electrolysis. The bonding system is what keeps electrolysis from damaging our boats.


I keep my SPARE ZINCS fastened on the propeller shaft inside my hull. They are close to the stuffing box. The black rubber with stainless bands is a stuffing box. And no, of course it is not square. This is a boat, where the head is a place you put your butt! Do not try to understand it.

The "real" zinc anodes are in the water. These two are still useful and I recommend every boater keep their spares inside and attached to the shaft. The reason to have bolted on zincs inside the boat is to prevent the shaft from coming out.

If there were a catastrophe such as a line being caught in my prop, those two should keep the shaft in the boat. A shaft falling out (and it has happened to others) generally sinks  the boat.


Also, having spares inside means should I need to replace a zinc anode at any time, I have one, er two, ready. And I can find them.


Keeping rope from wrapping around the shaft/propeller is a Good Idea. Unfortunately all too often when the words Good Idea are applied in a "marine application" the costs skyrocket. Fortunately Captain Richard discovered SALCA.

SALCA aka Sacrificial Anode Line Cutter Assembly

Same link made smaller: The ZincWarehouse.com SALCA page

Dauntless said "The one on the shaft is a combination steel cutter attached to a clamp on zinc anode. It costs only $60. Itís the second one Iíve put on and it works wonderfully. Half eaten, it tells me itís doing its job and no pieces of line wrapped around the shaft as had happened in the past."

This is his old SALCA at haul out, prior to replacement with a new one:

Available at the Zinc Warehouse, it's something you should consider if you don't have a line cutter already. I know I intend to order one next week. This is a Good Idea, and relatively inexpensive. I know it is a lot cheaper than hiring a diver to remove a line wrapped around the prop.

In looking at the unit, it appears that the blade (split into two pieces) could be attached to a donut shaped anode after the initial one needs replacement. It is stainless so I suspect that by drilling holes through a donut zinc I could through-bolt the blade pieces to a new zinc with relative ease. I will test that theory at some point.

Richard of Dauntless has a pair of websites that are wonderful. Visit:


The white yacht just to the right of center at a dock
is a sister-ship to Dauntless. She's a KadeyKrogen42.

Have you a SALCA or a standard line cutter on your shaft?
Are you glad you have it or was the unit a waste of money?

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