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Land and Sea Stern Jack

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Old 01-16-2016, 10:21 PM
  #21
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Yeah that is what I am missing, the one still attached to the drive. What are you asking for it?

Last edited by islander216; 01-16-2016 at 10:24 PM.
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Old 01-17-2016, 08:38 AM
  #22
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Quote:
Originally Posted by papps View Post
I am pretty sure I have that coupler for the stern jack. I will take a pic and post it tomorrow. Sold my old alpha SS a year or two ago and converted it back to the standard coupler before I shipped it.
I gained significant speed adding the stern jack to a 21' scarab and even more speed when I went to the alpha SS.
The stern jack seemed to work well on certain hulls but agree that it causes other problems the biggest being needing external steering.
The reason you gained more speed when you added the Alpha SS (shorter gear case) to the Stern Jack is actually quite simple. The further you extend a drive back from your transom, the further you need to move the propshaft up. Why? If you watch the way water comes off of a boat transom, it comes up on an angle. Getting back to my previous statement, you're chasing this angle / curve with your drive height.

I should also add that this same effect is why adding a Stern Jack generally decreases midrange fuel consumption. That would be because you now have more hydrodynamic drag - unless you raise your drive.

Finally, as this poster so correctly stated, adding all of that extra leverage greatly increases the strain on your steering components. Adding external ram hydraulic steering will help counter act this effect. Be very careful to check how much play is in your current steering system before adding a Stern Jack though. If you have lots of play in the baseline system, you will have one hell of a handful after you add the Stern Jack.
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Old 01-17-2016, 09:35 AM
  #23
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The 8" extension on a stern jack installation is after the pivot point so with positive trim the prop shaft travels higher. I have not done the math but would guess the 2 factors cancel each other out and you end up with the drive about the same depth........assuming a significant amount of positive trim.
Again, my hull was a shallow V, delta pad bottom which may not be pushing as much water away as a deep V like the baja. Land & Sea had a page where users posted results and there were quite a few that gained nothing or lost speed. Maybe someone can find that page and see if your baja was posted?

I have no use for this coupler so pay the shipping and it is yours.
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Old 01-17-2016, 09:52 AM
  #24
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Islander216, just remembered I also have the special tool for removing the large castle nut which you will need if you end up trying this.
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Old 01-17-2016, 02:16 PM
  #25
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I will take it for sure, just tell me what you need for the shipping and how you want me to send payment. I also have the tool, I have resealed a few Alpha drives over the years and have most but not all of the disassembly and set up tools.
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Old 01-19-2016, 07:33 AM
  #26
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I would say all boats respond differently, several years ago I installed a stern jack(new at the time) on a 21 checkmate with a 454 alpha, no other changes and picked up 7mph, the boat handled great, was really surprised, owner ran it that way for a couple of years with no issues that I heard of. went from 65 to 72
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Old 01-20-2016, 08:04 PM
  #27
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Ezstriper, to gain 7mph with no increase in hp is impressive. Wish I knew the depth of the drive on that setup.
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Old 01-21-2016, 09:01 AM
  #28
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no idea was years ago, he bought it new and helps install..just a 330hp 454
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Old 01-21-2016, 09:14 AM
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Just curious for those that had good results, what prop did you run before and after?
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Old 01-22-2016, 06:13 AM
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no prop change, was a mirage as best I can remember, we made NO changes other than the jack
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