sims super v jet drive problem or mismatch engine to impeller ?

Discussion in 'Jet Drives' started by james willingale, Oct 5, 2019.

  1. Yellowjacket
    Joined: May 2009
    Posts: 614
    Likes: 90, Points: 28, Legacy Rep: 447
    Location: Landlocked...

    Yellowjacket Senior Member

    I didn't realize you added that much weight aft with the engine swap. So yes, move the battery and anything else that isn't nailed down forward and if you have to you could also add a trim tabs to help you get over the hump. All of those are good ways to reduce the resistance and make it easier to get over the hump. As Beckmo noted the margin here is small, the faster you go the more power the unit can absorb, so the faster you go. Trim tabs likely can provide a good bit more lift and may be a good solution. As you noted earlier you were able to get over the hump when you had another person aboard and he was in the bow so you aren't that far off in the ability to get over the hump. When you start moving things like the battery up to the bow you actually move the CG a good bit because of the large amount of distance that you move that weight. I would do that first and/or have a friend or two come along and use that to get over the hump and then see what the high end performance looks like with the current impeller. It costs nothing to do that and it will tell you where you are at the high end. See what the top speed and engine speed are and if that works out, then you can readily address the planing with tabs that run the width of the transom on each side, If you want more aft lift at low speeds you could even install simple tabs with turnbuckles and set them to be level with the bottom of the hull. That effectively lengthens the hull and increases lift aft making it easier to plane off. Before you spend big money on new impeller and stators you need to figure out where you are with the present unit.
     
    james willingale likes this.
  2. james willingale
    Joined: Oct 2019
    Posts: 11
    Likes: 0, Points: 1
    Location: essex

    james willingale Junior Member

    Thanks guys this is starting to make sense to me now after you have explained how these things work i'm feeling hopeful that i may be able to get this boat right and up and flying across the water now. i'll do these things ASAP weather depending as its monsoon season here at the moment in essex and much of the UK at the moment after a nice summer and report back with the results maybe a few pic's or a vid if it all goes well. Thanks again for all your help yellowjacket,baeckmo,anthony goodson one day i might be able to help you guys.
     

  3. james willingale
    Joined: Oct 2019
    Posts: 11
    Likes: 0, Points: 1
    Location: essex

    james willingale Junior Member

    A nice bit of work this bit crazy to say the least 1000hp 13 ft jet boat

     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.