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Prop Help - Formula Br 280

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  • blamtro
    started a topic Prop Help - Formula Br 280

    Prop Help - Formula Br 280

    2000 formula 280BR. Twin 350 Mag mpi with bravo 3s, 2.0 ratio.

    Tried hill marine 4x4 24 p props but considering going down to 22. Loaded with 6 adults and 7 kids under 8 years old, I could only muster 3800 rpm at 38 mph via gps. This was the best result i could get playing with trim and tabs down.

    Same props with 4 adults, 4 kids under 8, I could get 47mph at 4400 rpm.

    Was surprised by the way the addition of 1 family (2 adults+2kids) changed WOT performance.

    Is this normal?

    im getting feedback that I should easily be able to turn 5000 rpm at WOT with this setup.

    where do I go from here? Compression test? Check drive toe in/toe out?

  • QBhoy
    replied
    Originally posted by tpenfield View Post

    OK. Was your RPM hitting the specifications for the engines with the original prop sets?

    If not, then you could certainly try the 22 P set, if you have any $$$$ left
    Only thing might be that I suppose there could be an issue with the engines. I would think the 26” props with a 2.0 ratio would be spot on, all being well. I honestly think the problem is engine performance related.

    Leave a comment:


  • tpenfield
    replied
    Originally posted by blamtro View Post
    tpenfield merc factory bravo 3 blade 26p
    OK. Was your RPM hitting the specifications for the engines with the original prop sets?

    If not, then you could certainly try the 22 P set, if you have any $$$$ left

    Leave a comment:


  • QBhoy
    replied
    Sounds like you have that covered but it worth me mentioning that I’ve went through 5 caps in 5 years with mine. Now also suspecting I have another failed half way through season. It will be 6 if you count one that was no good right out the box.
    Would also say that even if you have a little contaminated fuel...it will contaminate any amount of fresh fuel you put on top.
    Youll probably know already but these engines need iridium plugs or at least a minimum of platinum. Many make the mistake of putting on the normal carb ones. They just don’t run well at all with them.
    You will know I’m sure anyway.
    Seems a strange one. There’s no way it should be so poor in performance. I’d even think that should be a genuine touching on 60 mph boat perhaps. But certainly into the 50’s.

    Leave a comment:


  • blamtro
    replied
    QBhoy sparkplugs, cap and rotor are all in good shape, new at beginning of season. Fuel was fresh fill less then a week ago.

    Leave a comment:


  • QBhoy
    replied
    If someone was to ask me what this set up would perform like...I’d guess instantly that it would be a real rocket ship and easily in excess of 50 mph and likely more.
    I’d be thinking about replacing both diz caps...and if still no joy...look to what is common to both engines. As in the fuel.
    A friend has a maxum 2400 (26ft oal) with a single mag mpi and B3 26” props. It will rocket on the plane with 6 adults on board even with 4 of them sitting across the back seat. Not sure about top speed like that, but with 3 on board it will certainly and consistently do 5000 rpm and between 48-50 mph. Just as a comparison

    Leave a comment:


  • blamtro
    replied
    tpenfield merc factory bravo 3 blade 26p

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  • tpenfield
    replied
    What prop set was on there originally, before you 'tried' the Hill marine sets?

    Leave a comment:


  • AllDodge
    replied
    Your running WOT and getting 4400
    Add more weight and loose 600 rpms, that sounds about right

    If your normal load was 4A and 4K, then you need maybe the 22 4x4 or 24 3-blade

    The more weight, and where they sit, changes the boat performance every time.

    Leave a comment:

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