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648 War Eagle w/ Merc 30 Prop selection

Discussion in 'Boats, Blinds, & Gadgets Forum' started by kill em n grill em, Oct 10, 2018.

  1. kill em n grill em

    kill em n grill em Refuge Member

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    Genesee MI
    Good Afternoon,

    My dad just picked up a new rig last week and we were curious about the prop thats on it. I see online guys talking about hitting high 20's and even into the low 30's with a 25 hp engine but with 2 guys in it we topped out at 22 mph. When I looked at the prop selector that mercury has, the prop that was on it was one of their suggested sizes: 9.5x11. I was just wondering what size you guys run or have ran.

    Its a 648 war eagle with an 06 Merc 4 stroke 30 hp efi model.
     
  2. metalworx

    metalworx Refuge Member

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    My setup that I had was a 1651 Polarkraft with a 06 Merc 4 stroke 25 efi. I had the aluminum prop detuned to a 9 pitch and could achieve 24mph with 2 people in boat. Put that same load into a strong headwind and you could forget that! About 16mph then. Became a safety issue so I sold it and put a 40 efi 4 stroke on boat. No issues now
     
  3. CA Hunter

    CA Hunter Senior Refuge Member

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    You need a tach. Then you can decide what prop you need.
     
  4. calling4life

    calling4life Elite Refuge Member

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    Less motor in the water=less drag= more speed, generally. A jackplate could help. But yes, you need to know your RPMs, if you're top speed is achieved with the motor only getting to 5,000 rpms you may want to go down in pitch to a 9 pitch. If you're in the max rpm range, the jackplate is an answer to help some, otherwise you can play with chopper vs cleaver, cupping, and so on to try and get a little more. But if that boat needs more motor, get it more motor, it is one of the most widely universal recommendations from boat owners to put as much motor as you can on the boat. Not uncommon to see the phrase, "the max hp rating is the minimum hp you should put on."

    I'm in need of a new outboard myself, kind of sucks, as I don't have the coin to be re-motoring.
     
  5. mmayes

    mmayes Diver Forum Mod Moderator

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    I am currently running a WE 648 with a 00 Yamaha 4Stroke 25 and with 2 people running 25 consistently not sure of the prop pitch. You should be getting more out of your motor than that. Have you tried trimming the motor? Also could it be a long shaft motor on a Short transom?

    Mayes
     
  6. kill em n grill em

    kill em n grill em Refuge Member

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    It is a long shaft on a tall transom, so that matches up correctly.

    It has the power trim so it was easy to rule that out. When I was operating it I messed with the trim and it responded just as expected, trim down too much, I'd plow and drop down to 16 or so mph, trim up and I'd ride high in the front and drop down to 16-17. So with a good level trim, I was only seeing 20 into the wind and 22 with wind behind me.

    There is a trolling plate on it with a hydrofoil. I'm curious if this is causing enough drag to slow it down at top speed. I know they help with getting on plane but wasn't sure about how much it would effect top end. We have a tach on order that will be here next week.We may remove the trolling plate and see if it makes much of a difference.

    Thank you all for the responses.
     
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  7. CA Hunter

    CA Hunter Senior Refuge Member

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    When you get the tach, then you will have some data to discuss/analyze. Now you are shooting in the dark.
    In order to know something you need to compare RPM and speed. two factors. One is not enough.
    My boat was getting 22MPH with 30HP 2 stroke. After installing the tach, , new prop, adjusting the height, trim, hydrofoil and setback ( i put a homemade jack plate) i'm getting 28-32 depending on the direction of the tide, with 3 big boys 210, 215 and 250 LB, 24F battery, 6.5 gal gas tank 6HP kicker and fishing gear.
    So, data is everything, speculations will not get you anywhere.
    BTW, correctly installed hydrofoil (rather height of the motor) does not have any drag since at top speed it is above the water.
     
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  8. CJS

    CJS Senior Refuge Member

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    Make sure whatever pin you have the motor on isnt giving you negative trim.
     
  9. kill em n grill em

    kill em n grill em Refuge Member

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    Location:
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    A Question for all,

    The tach came in the mail today but we won't get to test it until the weekend more than likely.

    While I was running it I noticed the trolling plate was under water as well as the hydrofoil and with the mention of jack plates, we decided to take a look at where the cav plate was in relation to the bottom of the boat. Its currently about 2.5" below the bottom of the boat. Fortunately it is set in the very top hole so we can move the motor up on the transom to lose some drag. My question is, do you have to fabricate some sort of elevated transom mount or will the bolts be sufficient enough to keep the motor secure. Either way it needs to go up and we should be able to achieve that just by using the lower holes on the mounting bracket but we just want to make sure we're going about it the right way.
     

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