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  1. #1
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    Help prop question

    I have a 2006 PT 190 with a 90 HP Optimax with a 4 blade split fire 12.5 x 19 (just purchased). Mounted in the 2nd hole. I am getting 39 mph at 5180 rpms. These readings are from my Mercury VesselView. Does anyone know what I can do to get more speed. These readings are a 3/4 full load (1/3 tank gas) in boat with 2 people (450 lbs). Shoots out of the hole great and corners great I know I should be able to get at least 44 or 45 mph or so. I barely got 40mph with just myself. I bought the boat with a 24 pitch Laser II. That was like driving a stock Mack truck thru the swamp bog hence the 12.5 x 19. I would appreciate any input as funds will allow for the purchase of one more prop (SpitFire x7). I'm new here and hope I am posting in the right place. I posted this same question on the Tracker page too. Thanks and BBC Rocks. Fish On!!!!!!

  2. Member tjsellsfords's Avatar
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    Dec 2016
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    Kings Mountain, NC
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    #2
    You could go up one hole, but I'm not sure if you're going to get more than 2-3mph better with a hole change and/or prop change. What is your max RPM's on that engine?
    Last edited by tjsellsfords; 05-11-2021 at 09:42 PM.
    2017 Crestliner VT 18 DX
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  3. Member
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    warren mchigan
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    #3
    5750 rpms

  4. Member
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    Jul 2012
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    Windsor, Maine
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    #4
    I'd probably try moving the motor up a hole as mentioned

  5. Member Extremeboating's Avatar
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    May 2021
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    Concord, CA
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    #5
    There are several variables need to be accounted for. You need to determine where your motor sits at full trim. Meaning, once it is nice and level and parallel with the top of the water (in this case parallel with the ground) you can use a level to determine where perfectly level actually is. Once you have done that, you need to get a very long straight edge unless you are really good at eyeballing things and determine where exactly the underside of the cavitation plate sits on the transom. If it rests .5- 1" above then you should be in pretty decent shape and should not need to move the motor at all.

    That prop is WAY under revving your engine and you need to correct that. The majority of Merc 4's I see have a nominal recommended operational range of about 5500-6000. I'm going to assume yours is no different. However, before going too far into this, I would only address the prop issue once and ONLY once you determine exactly where on the transom your cavitation plate line is. These determinations are easy to make outside of the water.

    If you have determined the cav plate line is in a good spot on the transom then we need to get you up to the proper RPM range. Mercs prop selector page is scary accurate at determining the correct pitch prop for you, but you need to determine dry weights of your Tracker boat, current speed, current pitch prop, and average normal current operational RPM at WOT on your rig. All info which it appears you have.

    Take this in steps, as the name of the game is saving your wallet money and not chasing your tail doing things that may not necessarily need to be done. Feel free to PM me if you need help at any point. I'm always happy to help.
    Last edited by Extremeboating; 05-15-2021 at 02:24 AM.

  6. Member
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    #6
    Wow thanks for great info. I will be all over what you recomended. I have a 90HP Optimax. The mercury prop page said I should go with a 13x 17 4 blade splitfire. A dealer I called said the same thing. I will do what "you" said first before doling out any cash. Again Thanks alot.

  7. Member Extremeboating's Avatar
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    #7
    Quote Originally Posted by Crankbaitking64 View Post
    Wow thanks for great info. I will be all over what you recomended. I have a 90HP Optimax. The mercury prop page said I should go with a 13x 17 4 blade splitfire. A dealer I called said the same thing. I will do what "you" said first before doling out any cash. Again Thanks alot.
    That sounds about right for what you want to accomplish, all the while keeping you in a good RPM range. You're very welcome. In the quest for need for speed at least for boats, knowledge is king.

    I must say, however, if you want to confirm the pitch sizing that your dealer recommended you may want to plug in some basic info here on the Merc website. They are DEAD accurate. You will need some basic info in order to get the right sizing results though.

    https://www.mercurymarine.com/en/us/...lers/selector/
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