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Thread: Outboard Cavitation

  1. #1
    Join Date
    Oct 2007
    Location
    Bellingham, Washington USA
    Posts
    257

    Default Outboard Cavitation

    Hi, I have a 20' Bartender boat with 50 hp Suzuki in a well. The problem I'm having is whenever I get some eelgrass around the bottom of the outboard it will start to cavitate and send the rpms way up. Then I will have to stop the boat and clear the stuff from around the prop. It is a real pain in the butt. We get these eelgrass clumps floating all around here(San Juan islands) most of the year it seems. It doesn't happen at slower speed. I wonder if other people have had this problem with there outboards. As far as I can tell other boats around here don't seen to be having a problem. I have moved the cavitation plate down as low as it can go to see if that would helip. Nope. I try and avoid the stuff when I can see it but it is hard miss sometimes.

    Anyone else have this problem?

    Eric

    https://bartenderboats.com/
    "I see!" said the blind man who picked up his hammer and saw.

  2. #2
    Join Date
    Apr 2009
    Location
    Mountain lakes of Vermont
    Posts
    18,008

    Default Re: Outboard Cavitation

    How do you move the cavitation plate down on an outboard? It is a permanently fixed part of the outboard.

    I've had that problem in one of our lakes with heavy weeds. The weeds jamb up in the prop and there is no remedy but to stop, raise the motor and unwrap the stuff.
    I was born on a wooden boat that I built myself.
    Skiing is the next best thing to having wings.

  3. #3
    Join Date
    Oct 2003
    Location
    Valley of the Sun
    Posts
    119,318

    Default Re: Outboard Cavitation

    where exactly on the outboard does the eelgrass collect?
    Simpler is better, except when complicated looks really cool.

  4. #4
    Join Date
    Nov 2014
    Location
    Seattle, WA
    Posts
    5,691

    Default Re: Outboard Cavitation

    Various sorts of rope and weed cutters are available for outboards. Maybe something like this would work?

    https://www.ebay.com/itm/334335607884

    I have no experience with it myself but might be worth a try. A few years ago we got stuck in milfoil with Skookum Maru and had to spend some time poking at the prop with a boathook to get it all cleared out so I understand the problem.
    - Chris

    Any single boat project will always expand to encompass the set of all possible boat projects.

    Life is short. Go boating now!

  5. #5
    Join Date
    Oct 2007
    Location
    Bellingham, Washington USA
    Posts
    257

    Default Re: Outboard Cavitation

    I moved the hole outboard down not just the cavitation plate.

    The eel grass wraps around the leading edge of the under water leg.

    I’ll have to look into the weed cutter prop gard ideas.

    cheers
    "I see!" said the blind man who picked up his hammer and saw.

  6. #6
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
    Posts
    22,234

    Default Re: Outboard Cavitation

    Anti Ventilation Plate
    there is no such thing as a cavitation plate.
    Cavitation is when water boils on the blades of a wheel and causes pitting in the metal .
    Last edited by wizbang 13; 09-29-2022 at 04:58 AM.

  7. #7
    Join Date
    Mar 2007
    Location
    East Quogue,NY
    Posts
    25,767

    Default

    Nothing you can do but stop, reverse the engine to unwind the weeds, or stop and manually clear them, and then carry on. Avoid the mats as best you can.

    As for your observation that other boaters seemingly have less problems, it could be they are running with more trim. Also, the well may be somehow helping the weeds collect, versus other boats, most of which have no well.

    Kevin


    Sent from my iPhone using Tapatalk Pro
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  8. #8
    Join Date
    Oct 2007
    Location
    Bellingham, Washington USA
    Posts
    257

    Default Re: Outboard Cavitation

    Anti Ventilation Plate
    there is no such thing as a cavitation plate.
    Cavitation is when water boils on the blades of a wheel and causes pitting in the metal .
    Hey I knew that, I just wanted to know if you knew that .

    the well may be somehow helping the weeds collect
    I also considered that may have something to do with the problem but don't quite see how. It does make it hard to get at the prop.
    "I see!" said the blind man who picked up his hammer and saw.

  9. #9
    Join Date
    Oct 2007
    Location
    Bellingham, Washington USA
    Posts
    257

    Default Re: Outboard Cavitation

    reverse the engine to unwind the weeds
    I'll try this next time.
    Thanks
    "I see!" said the blind man who picked up his hammer and saw.

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