Jackplate Height

• Jackplate Height   by Curt on 23 Jul, 2015 08:57
• Got out with my boat yesterday afternoon and had a chance to run the outboard at WOT for a bit. I've only been able to do this once before, since installing the jackplate.
  
  My impression so far isn't good. I'm thinking that maybe the height on the plate needs to be lowered. Here's why.
  
  The boat is much more sensitive now when it comes to porpoising. I have to pay way more attention to trim levels and it porpoises a lot easier now.
  
  Also, I tend to have prop blowout while cornering now if I don't trim 100% all the way down.
  
  If I bring the boat down off of plane and make a hard turn and then punch it, it will blow out pretty badly too.
  
  Does it sound to you guys like I need to lower the engine height?
• Reply #1   by Bullet3119 on 23 Jul, 2015 09:07
• Do you have a prop to pad measurement at current height?
• Reply #2   by JackJ on 23 Jul, 2015 12:06
• Did you set the prop to pad back to the same as it was before the JP?  Start there if you didn't.
  
  And what you are saying does, sound about right for one that is a tad too high.   Maybe knock it down a 1/4" at a time to try.
• Reply #3   by Curt on 23 Jul, 2015 13:55
• Quote from: Bullet3119 on 23 Jul, 2015 09:07

  Do you have a prop to pad measurement at current height?
  

  
  No, I don't have that measurement right now. I will have to get it.
  
  @JackJ From what I could tell, we set the engine height back to what it was before the jackplate was installed. Maybe having the 6 inch setback requires it to be a tad lower than it was previously.
  
  I'll get the prop to pad measurement and post it here when I can.
  
  Thanks guys!
• Reply #4   by Bullet3119 on 23 Jul, 2015 14:18
• As was stated,  drop it 1/4" at a time until it feels right. That'll get you close until you can get it measured.
• Reply #5   by Curt on 23 Jul, 2015 14:24
• Thanks Calvin 
• Reply #6   by n2ratfishin on 23 Jul, 2015 20:20
• Take a sharpie and mark your JP as a starting point before you do anything.  For best results make sure both sides come down the same amount.  Sometimes you have to hop up and down on the motor anti cavitation plate before to tighten everything back down to get everything settled in.  I'm more of a move things an 1/8' at a time kind of a guy, but then again I've been known to make teeny tiny adjustments on the water when trying to get one dialed in just right LOL. 
• Reply #7   by Bullet3119 on 24 Jul, 2015 10:26
• I agree, 1/8" to get it right. 1/4" will get him in the ballpark though. Some jackplates will not move in 1/8" increments, just depends on the adjustment they use.
• Reply #8   by Curt on 24 Jul, 2015 12:11
• My jackplate is a TH Marine unit. Based on what I saw of it when installing it, adjustments can be made in very fine increments.
  
  There is a single bolt dead center that is used to raise and lower the unit, with bolts on each side to hold everything snug once adjustments are made.
  
  
• Reply #9   by JackJ on 24 Jul, 2015 12:32
• You might try out a different prop also. 
• Reply #10   by Curt on 25 Jul, 2015 15:38
• Quote from: JackJ on 24 Jul, 2015 12:32

  You might try out a different prop also. 
  

  
  Will definitely eventually need to try different props to get the best top speed. But I know that will cost money that I will need to plan for.
  
  My main concern right now is to get the best handling and performance out of the current prop 
• Reply #11   by Curt on 31 Aug, 2015 10:20
• Well, I made a couple of adjustments to my jackplate and I think I have it dialed in pretty good righ tnow.
  
  I adjusted it down 1/4 inch last weekend and tried it out. It was much better, with less porpoising and the top end was decent. Handling was also excellent. But it still felt like I was losing a bit of trim because it would start to porpoise a bit if I trimmed it up very much.
  
  So Friday night I dropped it another 1/4 inch in preparation for my club tourney the next morning.
  
  Saturday I had a chance to make a couple of good WOT runs and I was really, really happy with the way it performed!
  
  I hit a solid 53.4 MPH, which I had never done before, and no porpoising at all 
  
  I still haven't had a chance to try some tight turns to check for blowout, but at least the WOT performance is where I wanted it to be.
  
  I'm not sure, but in looking at the jackplate quickly, it seems like maybe I have it lowered to the maximum setting?? 
  
  I'll have to get some pics or a short video and post it here so I can get your feedback.
  
  I think at this point I've gotten all I can get from it without changing out the prop. And I know that props are expensive, so that's something that I can't do for the foreseeable future.
  
  The boat jumps out of the hole, literally, so I know I could move from the 19 pitch to maybe a 21 to gain some top end without losing holeshot.
  
  Definitely a future project when the budget allows. But for now, I'm happy with it 
• Reply #12   by fishon-son on 22 Jan, 2016 18:11
• hey curt , I know this is a older thread..but may I ask about the boat and motor /types?  what are you running in....?
• Reply #13   by Curt on 24 Jan, 2016 19:23
• @fishon-son I'm running a 2007 G3 HP180 (18 ft.) with a Yamaha 150 HP.
  
  The prop is a Yamaha Reliance series, 13 3/4", 19 pitch.
  
  I personally think it should be running a 21 pitch. Top end is a tad under 55 MPH. With a boat this light and a 150 HP, I should be able to get 60 MPH out of it with no problems.
  
  But a new prop is expensive and I can't drop $500 to try to get more top end out of it. 
• Reply #14   by Toad Orion on 20 Mar, 2016 21:49
• What are your rpm's @ WOT?

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