will kelp cutters help with Maine lobster traps

I've never needed to stop mid-ocean to clear a trap. They generally break off, and then you can clear them when you get to your destination. You may need to slow down to minimize vibrations.

I had an owner who had a new 56' MY and was complaining of vibration when he would bring his boat down from NC to FL. Started talking about manufacturer's defect, latent defect , all that good stuff that engineers like to hear.

Arranged to have him haul out in FL, low and behold we have a host of people ready to assess the situation and he is dragging rope/rode from a trap, all the way from NC, assuming it was a mechanical design error! Removed the line, checked the alignment, never heard back again on this "serious manufacturer design flaw".

Traps are usually coastal, so you most always have the chance to pull into port and assess the situation. But there is that one chance that the fouling becomes more serious and Line Cutters are cheap insurance.

There was a Nordhavn that had a line fouled on its running gear during the last Transatlantic Group crossing and was successfully cleared at sea. But I can guarantee you that guy was a real waterman, probably had more lifetime hours accumulated "in" the ocean than "on" the ocean.

I dove in the water 30 miles offshore of NJ once to check the running gear without a wetsuit or anything. I did have a dock line tied to my waist and the mate holding the other end of it. It was FREEZING cold and I wouldn't want to do it again.

Those are called Kort Nozzles and are very common among us commercial operators. Practically all tugs and push boats have them. Usually used with flanking rudders.
http://www.kortpropulsion.com/products/kort-nozzles

That's not what the fishermen in Maine have.

These are literally unsophisticated wire cages around the prop.

Here's a pic:

And that's a really nice one.

It looks like you'd lose half your thrust with that cage on. Do any pleasure boats use these?

Done rite, it may even help. Notice the last ring a lil wider. If I built that I would of made it a fatter ring, Like a Kort.
There is plenty of water getting to the prop. If not a high speed setup, maybe not so much air bubbles generated before the water hits the wheel.
I like this plan.

Is that a single screw work boat bottom?

I've seen this before, but I can't imagine putting something like that around my 32 inch props

Usually lobster boats, maybe some lobster yachts, but mainly a workboat thing.

That wire cage would fit fine on 32in wheels. My korts were on 60in

With no keel to use as structure? I cruise at 27-30 knots. Those things would have to attach to my bottom directly.. I couldn't imagine the stress they'd cause. Plus where is my speed and fuel efficiency going - south.

I'd have to regularly run in pretty junk laden waters to attach those cages to a recreational boat.

You don't want those on a recreational boat. The cages would be for a low speed commercial boat. Kortz nozzles would also generally be for a low speed commercial boat.

I thought so. Thanks for confirming. If I'm in and around the pots, fish nets or kelp I could understand. But not we guys/gals who run the LI sound and Block island sound mostly.

Kort nozzles are made for commercial boats doing less than 10kts in current. The wire cage pictured above would be fine for most planing hulls.

Single engine maybe - not twins.IMO

Prefer it on a single engine, but have had it on twins too. The builders put another balanced skeg in place. Add the flanking rudders for more control.
https://www.enecon.com/pdfs/newsletters/FL-012-Belgian_Kort_Nozzle.pdf
http://www.professionalmariner.com/...eers-towboat-has-unique-rudder-configuration/