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Thread: planing help

  1. #1
    Seaman Apprentice
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    Default planing help

    I need some help guys.

    i got a 16' lowe semi tunnel hull jon that i cant get to plane out.when i first got the boat it had a 25hp johnson that i got to plane once only because i hit another boaters wake. now i have a 35hp evinrude but still cannot plane.i was having alot of problems with boat drag because the motor sat to low mainly because of the tunnel.i bought a manual jack plate and got the cavitation plate about a half inch from being level with bottom and it now has a 4in offset but it still isnt enough.any ideas? i havent played with my tilt very much not sure which way does what. do you think i just dont have enough motor for the boat?any help greatly appreciated

  2. #2
    Chief Petty Officer BobGinCO's Avatar
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    Default Re: planing help

    I use a DeWalt DW733 for planing.
    2012 Tahoe 24' Fish-N-Fun Tritoon.
    115 Merc 4 Stroke w/13.75 X 13 3 blade aluminum prop
    Tow rig: The Galactica: 2004 F-250 w/V-10 Triton
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  3. #3
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    Default Re: planing help

    Probably need to raise motor. Got Pics of setup? tunnels are a different animal. Have contacted Lowe for help?

  4. #4
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    Default Re: planing help

    i can take a pic tonight.no havent talked to lowe but would a half an inch make that much difference?before the water out of tunnel was hitting foot and spraying everywhere.now that i got the jack plate the water is hitting just under the ribs above the cavitation plate and getting a little spray.the one and only time i know it was really planing, water was only going backwards no spray

  5. #5
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    Default Re: planing help

    Water is hitting above the vent plate. Not good. Where are your pics?
    Boat- ryder I don't want to be a Smart ***** but the set up on those boats need to to run off the water comming off the water from the transom in clean water. PICS PICS. I'm Done without PICS

  6. #6
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    Default Re: planing help


  7. #7
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    Default Re: planing help

    Still out there "Duckdown"?

  8. #8
    Commander jestor68's Avatar
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    Default Re: planing help

    When you say the boat won't plane off, what exactly is it doing? Is the prop ventilating and the motor reving, but not able to push it up onto plane?

    Those Lowe "tunnel" boats are referred to as "tunnel jets" by Lowe. I do believe they are intended to be powered by outboard jet drives for running in shallow water.

  9. #9
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    Default Re: Planing Help

    While I am no expert on OBs by any mean....

    I might suggest that you Trim IN all the way to start.
    Trim In = Bow Down; Out = Bow up!
    And/Or get some weight (Passenger?) into the bow to flatten the ride.

    The Anti-Ventilation (AV) Plate should be wet on the bottom and dry on the top when on plane.
    Just skimming the surface.
    Hold a long straight edge against the tunnel to see where it lands on the AV Plate.
    Start with the AV Plate an inch or two above the plane of the tunnel.

    If the prop Ventilates (Sucks Air), Lower the motor an inch.
    If it doesn't, keep raising the motor until it does, and then lower it back to where it didn't.

    TunnelTrim.jpg

  10. #10
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    Default Re: planing help

    ok my motor must still not be high enough because the water is hitting off of the ribs right above the cav plate so both sides of cav plate are wet.and i will try trimming it in all the way.my bow is coming up but not too much, im just not skimming the water

  11. #11
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    Default Re: planing help

    In My opinion, you are still to low. The only way to figure this IS to unclamp motor from bracket and place 2" square tubing under clamp and retighten. Water test. If to high go to 1 1/2" 1" untill you find the sweet spot. Looks like you have a long shaft motor on there. YES?

  12. #12
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    Default Re: planing help

    Quote Originally Posted by Mi duckdown View Post
    In My opinion, you are still to low... Looks like you have a long shaft motor on there. YES?
    Looks too long to me too.

    What is your transom Height? and Shaft length?
    The transom height is the distance from the tunnel to the transom edge.

    The shaft length is the distance from the bottom of the mounting clamp to the bottom of the AV Plate.
    The shaft length is hard to measure directly, but it will be a multiple of 5.
    So if it looks to be something like 21-1/2, it is a 20.

    TransomHeight1.jpg


    -----------------------------------------
    P.S. It is an Anti-Ventilation (AV) Plate not a Cavitation plate.
    Ventilation and Cavitation are two completely non-related phenomenon.
    Sorry to be the language Cop.

  13. #13
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    Default Re: planing help

    i will measure soon as i get home tonight.i dont think its a long shaft. from what ive seen other long shafts look like.thinking about what your saying about the spacer i dont think i can go 2 in without my clamps being right on the top edge of jack plate which i wouldnt trust but i can raise plate up a hole and get about an inch and then add a 1 in spacer and still keeps the clamps in a safe spot.will let you know soon.thanks

  14. #14
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    Default Re: planing help

    Boat- ryder. I quess I wasn't completly clear. My Bad. my post was just to give an idea of how high to raise it for a temporary fix. When that issuse is solved, then you can mount the motor permanently at what ever height is needed.

  15. #15
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    Default Re: planing help

    Ok I got ya, just measured, my shaft is 16 in and transom from top to top of tunnel is 14 1/4. If I didn't have the tunnel the av plate would prolly been in the perfect spot. Just for my knowledge 16 in is short shaft right? Looks like rain this weekend but will update soon as I can water test. Thanks for all the help

  16. #16
    Admiral smokeonthewater's Avatar
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    Default Re: planing help

    "bottom of the mounting clamp"

    the highest point inside the clamps that the top of the transom could possibly be.

    typically, 15" = short, 20" = long, 25" = extra long.... of course there ARE both longer and shorter motors than those.
    Kevin

    Quote Originally Posted by Tinnie
    But, where are the reevets?
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  17. #17
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    Default Re: planing help

    Actually 15" is a short shaft. Are you measuring from the bottom of the clamp that sits on the transom too the AV plate, just above the prop?
    Buy a raincoat.

  18. #18
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    Default Re: planing help

    yes just as the picture "unclewillie" posted it measured 16 in

  19. #19
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    Default Re: planing help

    Quote Originally Posted by Boat-ryder View Post
    yes just as the picture "UncleWillie" posted it measured 16 in
    That would make it a Short(15) Shaft Motor.
    The engine is trimmed out a hole and the clamp is at an angle, and you likely are not measuring Exactly Parallel to the shaft but at an angle.
    This is a difficult measurement and all the little variables tend to make the number a little bigger. 16 = ~15 = Short.

    If the transom is 14-1/4 = ~15 you are a close match.
    If the jack plate raises you 4 inches you should be good or possibly a little high.
    The other factor is the jack-plate and the Tilt combine to position the drive well behind the transom.

    While running at speed, as the water exits the tunnel it will tend to raise up to fill the hole left by the boats displacement.
    This raises the water line a bit. Think of it as a mini Rooster tail.
    That should be OK as the drive IS up a few inches to match.

    I would like to see another picture taken from about 5 feet Directly aft of the prop, looking up the tunnel.
    Position the camera EXACTLY at the level of the top of the tunnel.
    This will show us the relationship of the Vent Plate to the tunnel.

    A side view with someone holding a long straight edged object pressed against the tunnel and extending past the drive would help also.

    Having water on both side of the Vent plate is not an issue at this point.
    You are NOT on Plane, and a submerged vent plate is to be expected.

    It is time for another Sea Trial, Trimmed down all the way, and a passenger in the bow.
    We need to get it on plane before we can do the minor tweaking stuff!

  20. #20
    Admiral smokeonthewater's Avatar
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    Default Re: planing help

    Try this: pull the tilt pin out and trim the engine ALL the way down.... measure again..... I know pics can be deceiving but it still looks long to me... I think that MAYBE being trimmed out is throwing off your measurement.
    Kevin

    Quote Originally Posted by Tinnie
    But, where are the reevets?
    1981 Wellcraft V-20 CC Fisherman (FREE BOAT)
    1989 Wellcraft Monte Carlo 28(Build thread here)
    1992 Hotsports Jet'n'Cat Yam 701 WR3 drivetrain "SS George Washington"
    90's Yamaha WRIII and a pair of 95 Kawasaki ZXI-900's
    Fresh clean cheap oil is better then old dirty expensive oil any day

  21. #21
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    Default Re: planing help

    What you said makes sense I also believe the tunnel water is coming up and the jack plate raised the motor 3 inch exactly. Will take the pics you asked for in morning.now if trimming the motor all the way down lowers the bow I don't think that's my problem, like I said before the bow isn't coming up very high and keeping me from planing but I will try it anyway.just to be more specific I'm am pretty leveled out when running.i really just think the way the water out of tunnel is screwing me up. Pics soon. Also double checked my measurement and it is 16 in

  22. #22
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    Default Re: planing help

    0427131258.jpg0427131255.jpg0427131302[1].jpg





    sorry it took so long had to wait till i got to work to post pics.this is how it is sitting after i raised it an inch,havent got to water test but figured id get your opinion anyway.also took a pic of my clamps to show that i cant safely add any temporary spacers without the clamps being to high up.

  23. #23
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    Default Re: planing help

    What was I thinking!

    That tunnel is going to be out of the water when you are on plane.
    You may be too high instead of too low.
    Does the engine get a good bite and then rev up just about the time you think it should start to plane?
    The tunnel may be lifting the prop out of clean water and you start sucking air, Ventilating.

  24. #24
    Admiral smokeonthewater's Avatar
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    Default Re: planing help

    Willie, the whole point of the tunnel is to get the motor up high... the shape of the inlet of the tunnel lifts the water up to meet the motor


    I have a gut feeling that this is gonna come down to not enough horsepower.... I haven't had a tunnel myself but my understanding is that they aren't terribly efficient.


    Note that this sort of a tunnel hull is far different from a catamaran type that is also often called tunnel in that on this one, this tunnel starts amidships and the bottom is flat in front.
    Kevin

    Quote Originally Posted by Tinnie
    But, where are the reevets?
    1981 Wellcraft V-20 CC Fisherman (FREE BOAT)
    1989 Wellcraft Monte Carlo 28(Build thread here)
    1992 Hotsports Jet'n'Cat Yam 701 WR3 drivetrain "SS George Washington"
    90's Yamaha WRIII and a pair of 95 Kawasaki ZXI-900's
    Fresh clean cheap oil is better then old dirty expensive oil any day

  25. #25
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    Default Re: planing help

    Boat-ryder. That looks better. When test driving, don't be afraid to move the tilt pin out a couple holes. that should/might, bring the bow up some. Good luck Bud. Report back with results.

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