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Thread: Adding Transom wedge or thick washers to enhance outboard jet

  1. #1
    Member Sobie2's Avatar
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    Default Adding Transom wedge or thick washers to enhance outboard jet

    I have a friend who has run outboard jets for many years (including many years as a lodge owner). He swears that adding a few thick washers to the top mounting bolts really helps a jet hop up on plane by adding extra downward thrust (increasing the tilt) and thus lifting the stern.

    This is my second jet skiff. My first boat (1652 MVJT) I added flotation pods to and that helped reduce the bow rise when running alone. The boat also floated much more level at drift. My new boat (1860 MVJT) doesn't quite suffer the same amount of bow rise. But I am thinking what the heck I may as well try this thick washer trick. I am also interested in trying a 4 blade Stainless steel 7 3/8 impeller on my Honda 90. I am currently running a 7 3/16 4 blade Stainless steel impeller.

    So has anybody ever tried using either transom wedges or used washers to increase the downward thrust on their jet skiff?

    Sobie2

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    wrap a piece of thin rope under the transom and get it super tight and watch that bow do down. Depends on what part of the country you hear it but i've heard it called "cuban trim tabs to downeast trim tabs". It works just have to mess around with the thickness of the rope.

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    Adding the washers to the top bolts or wedges would probably do what you are looking for when getting out of the hole. I'd go with the wedges as they will spread the load out and not risk damaging your transom around the upper mounting bolts. The down side may be that in order to trim out for a decent motor angle for running your motor may move too far away from the transom causing a lot of excess spray or a loss in performance. But all the performance in the world doesn't help if you can't get out the hole when you need to. It's probably worth a try.

    How did you come upon the 7 3/16 impeller for the 90 honda? OB Jets only lists a 7 3/8 for the honda 90's and that one is a 3 blade. Wooldridge may make a 4 blade for this application though.
    Casey
    Yamaha Dealer
    Petersburg, AK

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    Member Sobie2's Avatar
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    Quote Originally Posted by Akfish1 View Post
    How did you come upon the 7 3/16 impeller for the 90 honda? OB Jets only lists a 7 3/8 for the honda 90's and that one is a 3 blade. Wooldridge may make a 4 blade for this application though.
    From Mr. Glenn Wooldridge himself!

    Sobie2

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    Well, he would know. Probably the best match for the motor then, I'd stick with it. I'm guessing going to 3/8" would slow the motor down and not perform as well as you are now.
    Casey
    Yamaha Dealer
    Petersburg, AK

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    Member Sobie2's Avatar
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    I got the transom wedges on last night, now I need to test it. Then I might order up a Wooldridge 7 3/8C 4-blade impeller.





    Sobie2

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    Test results?

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    Maybe this weekend... maybe.

    Sobie2

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    Well I put the transom wedges on back when I posted and they helped some. You get better results by putting an adult up by the bow. This past week I picked up a lightly used Wooldridge 7 3/8C impeller and it really worked great for planing out a load. The whole powerband was awesome! But you definitely lost top end speed. But it was fine for me because I needed the ability to hop up on step rapidly going downstream with 3 adults in a super shallow, narrow, and technical stream.



    Sobie2


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    WOW..... that was a reeeallly loong weekend....!
    “Nothing worth doing is easy”
    TR

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    Quote Originally Posted by Akgramps View Post
    WOW..... that was a reeeallly loong weekend....!
    What happens in Juneau stays in Juneau....
    "Now you know, and knowing is half the battle." - G.I. Joe

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    The wedges can help depending on the transom and boat you have. My transom is too straight up and down, adding wedges helped a lot with what I have.

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    Quote Originally Posted by Sobie2 View Post
    From Mr. Glenn Wooldridge himself!

    Sobie2
    When the 90 Honda first was fitted with a jet in the 1990s the Honda engineers wanted it to be fitted with a 7 3/16, they liked the higher RPM. . So for some years that was the designated Impeller for 90 Honda. But the 7 3/8 is better suited to the 90 Honda for hauling weight. The C Impeller you have pictured is a cutback C the blade is a little shorter and turns a little more RPM than a regular current C. Glen

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    Quote Originally Posted by acg515 View Post
    The wedges can help depending on the transom and boat you have. My transom is too straight up and down, adding wedges helped a lot with what I have.
    Is it a G2 that liked to porpoise?
    “Nothing worth doing is easy”
    TR

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