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Thread: V spray behind my outboard

  1. #1

    V spray behind my outboard

    I have 18 ft Hartley wooden boat with the fibreglassed hull, custom pod and 2 stroke V4 Yamaha 115. The boat is great and Yammy sings well but I am getting V spray. I fitted hydrofoil but that did not fix it but it has improved getting on the plane. I now suspect Yammy is fitted too low. Cavitation plate is about 75mm below bottom of hull. Does anyone have the answer?IMG_6230.jpgIMG_6350.jpg

  2. #2
    Ausfish Addict Chimo's Avatar
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    Jun 2006
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    Gold Coast

    Re: V spray behind my outboard

    Is the hydofoil sitting on the surface or just above it when the motor is trimmed back as when your running at a very fast cruise or above?

    If not then your motor is probably too low. The hydrofoil will certainly help getting on the plane but once your traveling fast the foil can add drag and may even throw some spray if the motor is sitting too low as you cannot trim it back and high enough to clear the water flow.

    The way I set my rigs up is best described as follows.
    If your arm was long enough could you slide your flat hand along the water surface and the hydrofoil when your running fast on smooth water with the motor trimmed back?

    With the optimum setup on a boat I had some time ago I could tow skiers etc in fresh water and turn really hard but the same boat in salt would break out on hard turns because it was sitting higher in the salt water.

    Try lifting it and if you start to porpoise you may need to go down a hole.

    Good luck with it.

    Cheers
    Chimo
    What could go wrong.......................

  3. #3

    Re: V spray behind my outboard

    Thanks Chimo, Hydrofoil fitting made no difference to V spray so it seems I got to try lifting the motor. Another question. I cruise at 40 kmh for prolonged period no problem and I can top at 52kmh for a short time but then it starts overheating and chokes back until alarm goes off, so I guess it is possibly corrosion deposits in the motor heads restricting water flow. Does anyone know if there is a wash that can get rid of the corrosion?

  4. #4
    Ausfish Addict Chimo's Avatar
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    Jun 2006
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    Gold Coast

    Re: V spray behind my outboard

    How long have you had the motor?
    Do you have the service history?
    Has it always been flushed after salt water use.?
    Do you know how it have been flushed?
    Not a Yamaha motor person but I seem to recall that they have narrow water passages, someone with more experience will probably comment.
    I have a mate with a Honda who had overheat issues and he tied all sorts of flushing stuff that didn't solve the issue. In the end the mechanic pulled it down and dug a massive amount of crap out of the passages and that fixed it. You may have to do the same.
    Who services It?
    Boat equals Bring Out Another Thousand. Lucky its not a BOATT or you add a ten factor and so on....

    Cheers
    Chimo
    What could go wrong.......................

  5. #5

    Re: V spray behind my outboard

    I have had it for 5 years (bought the boat with the beachhouse), I don't have past service record, I suspect it's not good. I have had no issues until I had it serviced then it started overheating, then I took it to another sevice place and they replaced thermostats etc. It now runs beautifully at 23 knots but tops out at 27 then starts overheating after a minute. I flush it with earmuffs for 2-3 min at idle. I only do 15-20 hrs/year. Compression is 120 on al 4 so worth keeping. If I use it 2-3 days in a row I will rinse it at the end.

  6. #6
    Ausfish Addict Chimo's Avatar
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    Jun 2006
    Location
    Gold Coast

    Re: V spray behind my outboard

    So it may have crap in the passages from previous owner.
    Hard to know for sure unless it gets pulled down.
    If you love it spend the $s or if not willing to spend just go slower.
    What could go wrong.......................

  7. #7

    Re: V spray behind my outboard

    You could try doing a vinegar flush. Many people have had good success with this. I would try that before lifting the motor.

    To check motor height, find a smooth bit of water and drive at your normal cruise speed and trim, and have someone trusty hold the wheel while you go and have a look over the transom at the leg. If the foil is under water, motor is too deep. It should be skimming the surface or be just above the flow. A motor set too deep will contribute to porpoising, lifting it higher helps reduce porpoising.

    Vinegar flushing: Here is a link to a thread on The Hull Truth that set it all out, its a bit of a read but the guy who started it knows what he is talking about.

    https://www.thehulltruth.com/boating...m-vinegar.html

    You dont mention what revs you can achieve at full throttle? Motor needs to be able to reach near its max rpm so that it is propped right. It helps to know in case you are overrevving or loading it up too much.
    Note to self: Don't argue with an idiot. They will only bring you down to their level and beat you with experience....

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