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Propeller Protection

Discussion in 'Technical Discussion' started by 1000 islands, Feb 21, 2017.

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  1. 1000 islands

    1000 islands Member

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    I hope I am posting in the correct forum...

    Most of my boating is in the 1000 Islands, St. Lawrence River & Lake Ontario and the 3 canal systems so I'm in shallow water quite often.

    After just picking up 2 props from the repair depot a thought came to mind, is there such a thing as prop protectors.

    I'm thinking of something that would be attached to the bottom of the boat and go around the propeller to keep from hitting the bottom.

    My thinking is something in a "U" shape with wings about 6" in width.

    The boat is a 1989 Carver 3607 with twin 454's and very expensive props attached to them.

    I have looked around and found nothing, but maybe I'm looking in the wrong areas.

    Any help would be greatly appreciated.

    Having them custom made is an option if I need.

    Thanks in advance
  2. PacBlue

    PacBlue Senior Member

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    Short answer is - typically not for pleasurecraft. Some commercial gill netters fabricate cage like protection to keep nets from entangling with props. There would be hydrodynamic lift that would occur when operating a "U" shaped bracket below the props, which could have a negative, or even positive effect, but would have to undergo a fair amount of trial/error/fitting to dial in, including multiple haul outs. If you make it too strong, you run the risk of punching the attachment points on the bottom of the hull through the hull bottom, so this may be a no go unless there are clever designs already in practice somewhere.

    An electronic alternative - side scanning sonar or orientate the transducer facing forward at the bow to get a forward scanning image to warn of impending obstructions. This is not necessarily a cheap option although and may not be effective at all speeds.

    Some reading: http://www.pbo.co.uk/gear/5-forward-looking-sonar-tested-29321

    Find a spare prop set on the surplus/used prop market for added piece of mind.
  3. 1000 islands

    1000 islands Member

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    I've got a couple of spare props, so there is no issue there, except that having to haul it out @ $200 + each time nand of course it is to the discretion of the marina if they are available that day.

    My thoughts are just about the protection of the extreme ends of the props.....what usual happens is they will just nick a rock/shoal and then everything is off balance and out the boats goes.

    Your comment about punching the attachments points has me thinking.....that in itself could make my idea a no-go.

    I'm hoping that someone here has experienced a similar situation and what, if any, issues were encountered.
  4. CSkipR

    CSkipR Member

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    Your best bet is to be extremely careful when your running in shallow water. Know the color of the water. Watch the water depth and know your hull depth.
    We all have the same concerns and trust me the 454 props are a lot less than a large yacht where many props run 20-50k.
  5. olderboater

    olderboater Senior Member

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    What kind of electronics do you have on board, especially with regard to depth? What is your draft? Are the areas you're encountering not marked and not on your charts? Is this the first time you've had problems or have you had repeated ones? How fast are you going when you hit?
  6. Capt J

    Capt J Senior Member

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    YES- it's called charts and a chartplotter. Knowing where you're going and avoiding places that are too shallow cures bent props.
  7. rcrapps

    rcrapps Senior Member

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    Kort nozzles come to mind. There was also some ring props years ago but have not heard any recent news on them.
  8. 1000 islands

    1000 islands Member

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    To answer olderboater and Capt J, I have charts, depth sounder and know the water fairly well.....and there are 1856 islands to boat around and dock at.
    But this is the St. Lawrence Seaway and the seaway controllers adjust the water depths for many different reasons.....projected rainfall, water level at various points, mostly the Montreal harbour,

    My draft is supposed to be 40" according to the manual, but it is all dependent on fuel, & water levels, all the stuff the admiral has brought on board and how many guests she has invited....so I always consider my draft to be 48".

    At my dock the water is usually around 10' deep, but I have left for a week and it's down a foot because the Montreal Harbour needs water because some heavy draft ship is in port.

    So when going between 2 islands that had 5' of water last week might only have 4' and I am heavier than usual and a cruiser has just went by pushing a 10' wake and when I go down after the wake BANG!!!! just enough to put a small ding in a prop, but enough to put it off balance.
  9. Lepke

    Lepke Member

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    Years ago (1960s) I had an I/O in partnership with a friend. He ruined at least 2 props a year. I never did. I think it's the captain.
  10. 30West

    30West Member

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    Anything you build around your prop will probably bend and contact the prop, resulting in more damage not less. A friend of mine has an old Chris Craft Commander with a deep keel that was intended to protect the props and rudders, among other functions. Adding more center keel might protect the props, maybe just a skeg, even if it bent it would be fair warning. If it were too sturdy, it could damage the hull instead of bending.
  11. Capt J

    Capt J Senior Member

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    I'm sure their is a website that will tell you at all times what the current depth should be (or correction should be).
  12. Rodger

    Rodger Senior Member

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    The Montreal section of Seaway adjust the levels of the canal but it takes months just to lower one inch.
    About twelve years ago Lake Erie was at a very high level and had to be lowered so the Welland Canal increased the water flow around the locks for ten months which did not effect shipping, but in the Montreal section of Seaway they had to stop shipping for ten hours a day for ten months two days a week because of the increased water flow ships could not navigate.
    When you see the water level drop one foot over night is because of storm wind blowing the water to the west end of Lake Ontario which will last for one or two days.
    As Lake Erie is a shallow lake I have seen marinas in Buffalo with no water as the wind is blowing down the lake. There were many days this past year when ships had to go to anchor in Lake Erie as there was no enough water.
    https://www.google.ca/search?q=seic...v&ved=0ahUKEwiH7JyW6qTSAhXh7YMKHXY8CWwQsAQIIA
  13. 30West

    30West Member

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    My boat draws about the same as yours, and I'll not intentionally go into water I think is 5' deep. If your props are a foot off the bottom, they are pulling things off the bottom, like nets and lines and things that can cause problems. A foot-tall obstruction isn't unlikely, an old log or rock or rusty barrel. I don't know what to say about those pesky ten-foot wakes!

    Adjust your steering nut, and you will have fewer prop strikes.
  14. 1000 islands

    1000 islands Member

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    Your statement of levels might be true regarding the Welland Canal, but the Seaway does not use locks to alter water depths, they use the dams and the one at Iroquois is the one that affects the 1000 Islands the most. And when they adjust the flow it doesn't take log to change the levels up or down in a matter of days.
  15. 1000 islands

    1000 islands Member

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    There are many sources that advise water levels, but only at the area they measure. As an example, the water level at Gananoque can be 6-8" different than at the 1000 Islands bridge and that's only a distance of about 30 miles or 50 kilometres.
    And of course the wind makes a big difference. It can change by 15 knots or more from morning to afternoon.

    When I used to keep my boat at the Ivy Lea Club there were many occasions when those who reversed into their slip facing north/south, had to wait until after sundown before the winds would stop and at that time thelevel at the docks would change by a foot some days.

    The river is wide and flows from the west, the same way the winds blow from most of the time and that affects the levels quite a bit.
  16. 1000 islands

    1000 islands Member

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    That comment has got me to thinking......good point and most likely why there is no such a product easily found.

    Thanks 30West
  17. Seasmaster

    Seasmaster New Member

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    1000 islands said:
    "My draft is supposed to be 40" according to the manual, but it is all dependent on fuel, & water levels, all the stuff the admiral has brought on board and how many guests she has invited....so I always consider my draft to be 48".."

    and then said:
    "So when going between 2 islands that had 5' of water last week might only have 4' and I am heavier than usual and a cruiser has just went by pushing a 10' wake and when I go down after the wake BANG!!!! just enough to put a small ding in a prop, but enough to put it off balance."

    If I might be so bold to suggest, that if your draft is 48", and there is only 4' of water. . . there is immediately a problem, irrespective of a wake!!

    Another issue you should thoroughly acquaint yourself with is the phenomena of "squat" of a vessel, and how it is magnified in shallow water. From what you've described in your operational theater, you will constantly be dealing with it. And while you are discovering the vessel's squat characteristics, take note of how the vessel's maneuverability is impacted by "shallow-water phenomena". Aside from being quite the eye-opener, you most likely will save a bunch on hull damage AND prop damage.

    Fair winds and following seas, 1k islands!

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