Prop line cutters

[backinblue]

I know this has been discussed in other threads but not sure if there is a thread dedicated to the topic. If so, I apologize in advance for the redundancy. I would like to add a line cutter to my prop/shaft next spring. There are quite a few on the market. I haven't found very thorough reviews and comparisons online so I thought I would ask here for opinions. Spurs look like they should work very well and I've seen some impressive demos at boat shows. But my criteria is to not pull the prop or drill any holes so that leaves me with the disc type cutters of which there are many. Shaft Shark, Shaft Razor, Prop Protector, Piranna, etc. I tend to think the serrated blade would work better than the straight blades, but some say the straight blades are better at low speed, like around a dock as the serrated ones can catch a line w/o cutting it. I've watch the youtube videos, but haven't found a really good comparison of all the different disc type cutters. I don't want to shop just by price. Thoughts?

 

[ksanders]

I know this has been discussed in other threads but not sure if there is a thread dedicated to the topic. If so, I apologize in advance for the redundancy. I would like to add a line cutter to my prop/shaft next spring. There are quite a few on the market. I haven't found very thorough reviews and comparisons online so I thought I would ask here for opinions. Spurs look like they should work very well and I've seen some impressive demos at boat shows. But my criteria is to not pull the prop or drill any holes so that leaves me with the disc type cutters of which there are many. Shaft Shark, Shaft Razor, Prop Protector, Piranna, etc. I tend to think the serrated blade would work better than the straight blades, but some say the straight blades are better at low speed, like around a dock as the serrated ones can catch a line w/o cutting it. I've watch the youtube videos, but haven't found a really good comparison of all the different disc type cutters. I don't want to shop just by price. Thoughts?

I have shaft shark. Don't know if they work for sure because I've never been caught up, which could be taken to mean they work great.

 

[Jeff F]

I had a Piranha unit installed a month ago on the recommendation of the yard guys in Nova Scotia who work on the fishing boats.

Last week I was anchoring amongst lobster pots and picked up a line while I was operating at low speed. Initially the motor stalled, then I restarted and put it in gear and the cutter did its thing and I carried on. A diver unwrapped the line from my prop later.

I'm sure the cutter kept me from being disabled by the entanglement. Glad to have it.

 

[HopCar]

From Practical Sailor Magazine: Three of the most popular line/net-cutting devices are the Prop Protector (www.prop-protector.com), the Spurs (www.spursmarine.com), and the Shaft Shark (www.ab-marine.com). PS compared the Prop Protector and the Spurs back in 1996. Testers favored the less-expensive and easier to install Prop Protector, but both worked well. If youre on a really tight budget, try a serrated knife lashed to a boathook. If you happen to live in Maine or elsewhere with lots of lobster pots, its always a good idea to keep a wetsuit, snorkeling gear, and a sharp knife on hand, even if you have a line cutter.
I had Spurs for almost thirty years on my boat. I know I hit lines at least twice but never got stopped.

 

[Ken E.]

Had Spurs, now have Sharks, which are simpler with no anode required. Do they work? I don't know but I've never been stopped by a wrapped-up line. Yet.

 

[Comodave]

Had Spurs, now have Sharks, which are simpler with no anode required. Do they work? I don't know but I've never been stopped by a wrapped-up line. Yet.

Do you mean that you haven’t deliberately run over some line to test them???

 

[Ken E.]

Do you mean that you haven’t deliberately run over some line to test them???

Good point! I will do that next summer, for sure!

 

[Comodave]

Good, let us know how they perform…

 

[FoxtrotCharlie]

I put the 'cheap' ones (includes zinc's) on at last haulout. Ran over a crab pot last week just below St Pete (FL) - engine hesitated then recovered and still running great. Pleased so far.

 

[DDW]

Yachting Monthly did a fairly extensive test which can be found here. Their conclusion seemed to be that most of them work, the scissors type perhaps a little better for some things. It may come down to price and what is easiest to fit on your particular boat.

I've tried a knife and a sawsall blade taped to a boat hook, given enough time and perserverance you might succeed. There is a knife made just for this though, and it really works.

 

[Keysdisease]

The shaft shark and shaft razor (disc cutters) have 2 serrated cutting edges and can be installed without pulling the prop. Most of the other disc non serrated units have just the perimeter cutting edge

The Spurs (scissors type cutters) as mentioned call for drilling/taping and anodes. Another consideration is the precise alignment these units need. Installed at a boatyard with no thrust on the shaft, and then when under thrust the shaft may move forward and aft a mm can cause a misalignment. These also occasionally can induce vibrations from the off center weight of the shaft component.

I found this video test pretty good. They all cut something, some cutters cut some things better than others, but overall I think the conclusion of this test is they all work, it just depends

 

[backinblue]

I had a Piranha unit installed a month ago on the recommendation of the yard guys in Nova Scotia who work on the fishing boats.

Last week I was anchoring amongst lobster pots and picked up a line while I was operating at low speed. Initially the motor stalled, then I restarted and put it in gear and the cutter did its thing and I carried on. A diver unwrapped the line from my prop later.

I'm sure the cutter kept me from being disabled by the entanglement. Glad to have it. View attachment 123130View attachment 123131

Thanks for the real-world example! As a follow-up, do you apply any anti-fouling to the cutter as well as the rest of your running gear?

 

[Jeff F]

No. I generally keep moving and haven't had growth problems on the running gear so far.

 

[backinblue]

Being in salt water, barnacles are pretty prevalent here especially on underwater metal. My boat gets used quite often but not constantly. My boat came from fresh water and it was never an issue there.

 

[mvweebles]

I used Spurs for years. I replaced them once due to something that broke (don't remember). There is also a bushing that needs ocassional replacement as I recall. When I last hauled, the shaft-mounted part had shifted enough that the stationary keeper-part no longer lined-up so they were rendered ineffective. I realize it was likely an install error, but still, these are relatively high maintenance compared to the Shaft Shark. When I read the Practical Sailor review coupled with the video posted above, I decided to go with Shaft Shark. They also meet OP's desire to not pull the prop shaft.

Good luck -

Peter

 

[backinblue]

I used Spurs for years. I replaced them once due to something that broke (don't remember). There is also a bushing that needs ocassional replacement as I recall. When I last hauled, the shaft-mounted part had shifted enough that the stationary keeper-part no longer lined-up so they were rendered ineffective. I realize it was likely an install error, but still, these are relatively high maintenance compared to the Shaft Shark. When I read the Practical Sailor review coupled with the video posted above, I decided to go with Shaft Shark. They also meet OP's desire to not pull the prop shaft.

Good luck -

Peter

Thanks for the feedback. I will definitely go with a disc type over a Spurs type. I was leaning toward the Shaft Shark but the Piranna also looks interesting and a positive experience from a member here, so that may end up being the one for me. It's a little wider but I have the room and filling up the gap between the cutlass and the prop may actually be an advantage. There is a cutter made by R&D that is specifically designed to do that, but I don't want to drill a dimple into my shaft for a set screw if it's not needed.

 

[Hippocampus]

The hook knife from sailors solutions does really work. Have had scissors and corrugated. Both have failed in poly nets. Both work fine with a single rope. This is with low hp sailing auxiliaries turning maxprop or folding. Problem has been netting doesn’t get down close enough to shaft to have a good effect. Occurrence is rare over 35 years but seemingly always at night while in a channel with shoaliing on either side. Usual culprit is the fine gill nets that get detached from their rig. Anchor launch dinghy and rip away with the hook knife. No need for a diver. +1

 

[Jeff F]

Thanks for the feedback. I will definitely go with a disc type over a Spurs type. I was leaning toward the Shaft Shark but the Piranna also looks interesting and a positive experience from a member here, so that may end up being the one for me. It's a little wider but I have the room and filling up the gap between the cutlass and the prop may actually be an advantage. There is a cutter made by R&D that is specifically designed to do that, but I don't want to drill a dimple into my shaft for a set screw if it's not needed.

The installer of mine was concerned about fitting - it shouldn't block flow through the cutlass bearing, but needs to sit on the shaft before the taper begins. Make sure you check the taper with calipers. On my boat the taper begins an inch or more in front of the prop. The gap may not be as big as it first appears.

 

[backinblue]

The installer of mine was concerned about fitting - it shouldn't block flow through the cutlass bearing, but needs to sit on the shaft before the taper begins. Make sure you check the taper with calipers. On my boat the taper begins an inch or more in front of the prop. The gap may not be as big as it first appears.

THanks I did measure with calipers and there is a taper but the taper ends just a bit forward of the prop. I have about a good 1.5" of parallel surface so I should be ok with any of these, but I appreciate your point about water flow through the cutlass. Probably best to not be too close to the bearing housing. Mine looks like this:

 

[jleonard]

I used Spurs for years. I replaced them once due to something that broke (don't remember). There is also a bushing that needs ocassional replacement as I recall. When I last hauled, the shaft-mounted part had shifted enough that the stationary keeper-part no longer lined-up so they were rendered ineffective. I realize it was likely an install error, but still, these are relatively high maintenance compared to the Shaft Shark. When I read the Practical Sailor review coupled with the video posted above, I decided to go with Shaft Shark. They also meet OP's desire to not pull the prop shaft.

Good luck -

Peter

And on the other hand...
I had Spurs on my old Mainship 34 for 13 years. Ii changed that bushing one time , after about 9 years. It never got out of alignment or adjustment.
I also did not have to change zinc every season, more like every other season.
I know it cut lines at least 2 times during the time they were on. Always a loud "thunk" then I would look back and see the buoy floating.
And never found a trace of line left wrapped around the prop or shaft.
I'm definately a fan of Spurs.

 

[Mischief Managed]

I installed Shaft Sharks last year and spent the Summer cruising the New England Coast. I have no idea if I picked up a rope or not, but the shafts were rope-free when we pulled the boat last month, so...

I was considering Spurs, but I do not have enough space between the struts and props to use them.

Consider adding a helmet to the list of things necessary to wear while cutting lines off your prop shafts. A wake or wave could easily lift and then drop the boat on your head while you are under the boat cutting line.

 

[mvweebles]

And on the other hand...

I had Spurs on my old Mainship 34 for 13 years. Ii changed that bushing one time , after about 9 years. It never got out of alignment or adjustment.

I also did not have to change zinc every season, more like every other season.

I know it cut lines at least 2 times during the time they were on. Always a loud "thunk" then I would look back and see the buoy floating.

And never found a trace of line left wrapped around the prop or shaft.

I'm definately a fan of Spurs.

Spurs definitely work. I was with a friend on his 46 foot sailboat from Long Beach to San Francisco and we picked up something off Ocean Beach just south of the GG Bridge around midnight. Definitely made a loud bang!

Intuitively, given the scissor action of Spurs, my original thought was they would work better than single blade types. When I saw the research that they both work well coupled with inherently lower reliability of a multi-part system (that requires prop removal), was an easy decision to move away from Spurs. But when properly installed and maintained, they definitely work.

Peter.

 

[neworleansrich]

I have 2 sets of Spurs for 2.5inch shafts to sell. PM me if interested.

 

[backinblue]

And on the other hand...
I had Spurs on my old Mainship 34 for 13 years. Ii changed that bushing one time , after about 9 years. It never got out of alignment or adjustment.
I also did not have to change zinc every season, more like every other season.
I know it cut lines at least 2 times during the time they were on. Always a loud "thunk" then I would look back and see the buoy floating.
And never found a trace of line left wrapped around the prop or shaft.
I'm definately a fan of Spurs.

I don't doubt Spurs work great, just that they are more complicated, not only for install, but also alingment with and w/o load to be sure the proper engagement of the moving and fixed knives. The split disc type are a much easier DIY install in a couple minutes with no drilling. I've seen Spurs demonstrated at a boat show and they looked impressive cutting a pretty good size line with ease. I just don't want to go through the install or pay to have it done. I've boated for years with nothing and never had a problem, but a few close calls with dark and partially submerged buoys got me thinking. I'm normally not boating at night, but rough conditions and strong current in daylight, can still make them hard to spot at times. I did suck a bow line into my thruster last summer but that's a different scenario. Thruster prop replacement is on the list for spring.

 

[MichaelD]

Salca

I just installed SALCAs (Sacrificial Anode Line Cutter Assembly), which are a serated disk built into a zinc. After looking at a couple videos of tests, it seemed like they all worked pretty good, and these were about the same configuration, and cost $40 each vs. a lot more for others. I painted over the zinc so that it doesn't sacrifice to make them last longer (obviously, have separate zincs for that purpose). Haven't hit anything yet to test them. Maybe I'll go looking for some of those crab pots that always seem to be placed right in a restricted passage (grrrr).

 

[backinblue]

I just installed SALCAs (Sacrificial Anode Line Cutter Assembly), which are a serated disk built into a zinc. After looking at a couple videos of tests, it seemed like they all worked pretty good, and these were about the same configuration, and cost $40 each vs. a lot more for others. I painted over the zinc so that it doesn't sacrifice to make them last longer (obviously, have separate zincs for that purpose). Haven't hit anything yet to test them. Maybe I'll go looking for some of those crab pots that always seem to be placed right in a restricted passage (grrrr).

I've seen those online as well. Does the blade appear to be sharp and strong enough for the job?

 

[MichaelD]

Yes. The blade is quite sharp, and seems to me heavy enough, about 3/16" thick.

Also, I should mention that these are of the split-ring variety so can be mounted on shaft in place.

 

[Mischief Managed]

I just installed SALCAs (Sacrificial Anode Line Cutter Assembly), which are a serated disk built into a zinc. After looking at a couple videos of tests, it seemed like they all worked pretty good, and these were about the same configuration, and cost $40 each vs. a lot more for others. I painted over the zinc so that it doesn't sacrifice to make them last longer (obviously, have separate zincs for that purpose). Haven't hit anything yet to test them. Maybe I'll go looking for some of those crab pots that always seem to be placed right in a restricted passage (grrrr).

I tried those. The first time, that I know of, that I put one of them to use, the rope pretty much turned the cutter inside out and it took me an hour to cut the rope off the shaft with a steak knife. Not impressed... I bought Shaft Sharks shortly afterward and so far so good.

 

[MichaelD]

That's not encouraging, but good to know.

 

[backinblue]

Just my inexperieneced opinion, SALCA makes sense to me if you use it as intended. Meaning, use it as an anode and you get a line cutter for very little money as a bonus. For the dedicated purpose of line cutting, I'm guessing the Shaft Shark or similar devices will work better albeit, at quite a bit more money. But if it saves you when you need it to, the value is priceless. My biggest worry is snagging a line in rough weather or at night which is more likely than on a nice day. That could make going into the water dangerous if not impossible. I guess that's when you call for help, but even that would make for a really bad day if you are stuck with no power in bad conditions.