Thread: Boat set up

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  1. #1
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    Boat set up

    I have a 18'8 cobra bass boat. I run run a tempest 23 p.. I am running at 54 mph ( WOT) and my RMP's are 5000 and my water pressure is 15 to 18. My question is how do I get RMP's. The motor runs great but I should be getting more RMP's. I also have a manual jack plate.

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    #2
    Can you give any motor details? Hard to tell without knowing that. Also how much additional weight in boat? Speed, rpm's and speed all sound a little low but need complete motor details...
    96 Bullet 20cc, Yamaha OX 250+, 10" jack, labbed 30" Bravo LH w/1.25" exhaust pipes, counter rotating Bob's lower, it goes faster when you spin it the other way...

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    #3
    Might have a bad coil.

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    #4
    Just fishing stuff with 4 batteries. The boats empty weight 1400 lbs.... I am running 53 to 54 mph wot bit my RPM's are at 5000. I have a merc EFI 150.

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    #5
    Quote Originally Posted by grout-scout View Post
    Might have a bad coil.
    How would I know?

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    #6
    Does sound like motor issue cuz you should be able to spin a 23 higher than that...
    96 Bullet 20cc, Yamaha OX 250+, 10" jack, labbed 30" Bravo LH w/1.25" exhaust pipes, counter rotating Bob's lower, it goes faster when you spin it the other way...

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    #7
    Quote Originally Posted by coachallen View Post
    How would I know?

    Truthfully, take it to a shop. I know that nobody wants to spend the money, but until you really know what the motors doing you will just be wasting money on guesses.

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    #8
    Sounds like you got the right prop if your motor was 100%. But it does sound like you are a little short on power for whatever reason. Might even be around 58-60 mph when she's running perfectly. Ask your local reputable mechanic for his opinion too and then proceed from there...
    96 Bullet 20cc, Yamaha OX 250+, 10" jack, labbed 30" Bravo LH w/1.25" exhaust pipes, counter rotating Bob's lower, it goes faster when you spin it the other way...

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    #9
    They motor runs great it just does not have enough rpm's. I will take it to my mechanic.

  10. Dam Fool rangerbobber's Avatar
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    #10
    What is your prop to pad measurement? Sounds to me like the motor might be too low, should be around 3.5", see if that doesn't get you up to around 5700 rpm but keep your eye on that water pressure gauge, no lower than 10-12

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    #11
    Not sure he can gain many rpms even if he’s p2p low.

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    #12
    Quote Originally Posted by grout-scout View Post
    Not sure he can gain many rpms even if he’s p2p low.
    So If I raise the motor I will NOT gain any rpm's?

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    #13
    Quote Originally Posted by rangerbobber View Post
    What is your prop to pad measurement? Sounds to me like the motor might be too low, should be around 3.5", see if that doesn't get you up to around 5700 rpm but keep your eye on that water pressure gauge, no lower than 10-12
    Ok will do

  14. Dam Fool rangerbobber's Avatar
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    #14
    Quote Originally Posted by coachallen View Post
    Ok will do
    The other thing to consider is your tach accuracy, how is your holeshot with all pvs holes open full?

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    #15
    my holeshot is great. I beat most boats in a short run.

  16. Member Garfish's Avatar
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    #16
    Have you checked your throttle plate to see that it's wide open when the throttle handle or hotfoot is pushed all the way? If it's WO then you need an engine computer analysis and compression check.

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    #17
    You have a 1400 lbs boat with a 150 on it with 4 batteries in the rear getting 5000 rpm's and 54 mph and those numbers are just about right with a 23" prop. Check the prop to pad measurement before you do anything else and see if it's around 3 1/2" under now. If it is you can start raising it 1/4" at a time until you gain rpm's but not speed, loose water pressure or bow lift then drop it 1/4" and you should be right. Don't let your water pressure get below 10 lbs at wot and you may have to trim down in tight turns to keep your water pressure up. It may also porpoise if the prop is worn.

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    #18
    Quote Originally Posted by mdtritn21 View Post
    You have a 1400 lbs boat with a 150 on it with 4 batteries in the rear getting 5000 rpm's and 54 mph and those numbers are just about right with a 23" prop. Check the prop to pad measurement before you do anything else and see if it's around 3 1/2" under now. If it is you can start raising it 1/4" at a time until you gain rpm's but not speed, loose water pressure or bow lift then drop it 1/4" and you should be right. Don't let your water pressure get below 10 lbs at wot and you may have to trim down in tight turns to keep your water pressure up. It may also porpoise if the prop is worn.
    Okay thanks

  19. Member MatMagni's Avatar
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    #19
    Hi guys, I have the same problem with my boat:
    Triton TR186 2005 mercury optimax 150 2009
    6'' idraulic plate - 23 tempest plus
    4 batteries, livewell full , 2 light guys, all fishing stuff
    max speed 54/55 mph at 5.000 rmp

    I don' t find any solution to find rpm and top end...can you help me please ?!
    Tks
    2006 Triton Tr186 / 2011 Mercury 200 Optimax

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    #20
    Mat check your gas lines and see if they are the old gray with red letter lines or the new gray with black letter lines. You should read this sticky post too and do everything on the list if your gas lines are the old ones. http://www.bbcboards.net/showthread.php?t=22490 What elevation are you running at now. With that load you may not gain anything but it's worth checking.

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