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Thread: Plowing the water

  1. #1

    Default Plowing the water

    Hey All,
    A buddy has a 1756 Alumacraft semi-v w/ an '07 90/65 Yamaha. He plows water really bad at faster speeds. When he is cruising at what we are guessing is 4200 rpms (no Tach) the boat is on step and goes well. When he pushes the rpms up the front end plows the water something fierce. We have tried messing with the weight distribution and trimming the motor. Trimming helps a smidge but not much, you best be wearing rain gear. Any ideas on what the problem is?
    Henry Bowman for President

  2. #2

    Default Plowing

    It almost sounds like the motor is set at a wrong angle as the rpm increases the front goes down. Look at the motor from the side and see what it looks like in relation to the boat. good luck

  3. #3


    If the boat is a used boat and has some bottom damage at the transom that could be the problem. Dents at the transom make a hook in the bottom that act like trim tabs and push the bow down. Glen

  4. #4
    New member
    Join Date
    Jun 2007

    Default More on used boats

    I agree with Glen that plowing issues normally happen on used boats when the bottom at the transom is bent in. It does not take a lot to force the bow down. I can't recall if that boat has a tab sticking out the stern, but if so and it is bent down, it too will cause the bow to dive.
    Also look at the whole bottom. I have seen boats that were bent more towards the center from years of use or even from a bad trailer.
    If the bottom is good, then like Big Bend says, look at your trim. If you don't have hydraulic trim then you should have a bar that you can move on the engine transom mount. The further forward and down the bar, the more the nose will dive. If you were to find that is the problem, you'll know you've moved the bar too far if the bow starts to porpoise up and down.

  5. #5
    Member Maast's Avatar
    Join Date
    Mar 2008
    Anchorage, Alaska, United States


    If the boat bottom is bent, or even if you have a big enough dent from amidships on forward the dent/bend will actually cause a partial vacuum and "suck" the bow down when you get up to speed - making the boat plow.

    Have to be a big dang dent though, like the others have said its probably a motor trim or a boat trim problem.
    2696 Sea Raider Pilothouse

  6. #6
    Member Akgramps's Avatar
    Join Date
    Apr 2008
    Last civilized place on the planet


    Does this hull have a tunnel?

    If so, Is it a prop or jet tunnel, I have seen some dealers hang a jet on a prop tunnel, and if this is the case perhaps the jet is set too low?
    “Nothing worth doing is easy”

  7. #7


    Thanks for the answers. The boat is not a tunnel and the motor has the correct angle from what we can tell. Any other ideas.
    Henry Bowman for President

  8. #8
    Join Date
    Apr 2006


    Trim. I try to trim to where the spray is coming out about 2/3 to 3/4 to the rear of the boat. The steering with a jet will feel a little loose at that point and really loose beyond that point. I get on step better with the trim tucked under and milk it off as I get going. But I don't have a semi-vee. The boat could make a lot of difference.


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