# Manual jack plate installation help



## Tom_C (Dec 10, 2006)

If your transom is 20".
Your 20" shaft is around 21.5" long.
Your Jack Plate has 6"

I would mount the Jack Plate 3" above the transom, but that just my opinion.


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## Tsport (Jan 4, 2007)

Thanks Tom! 
Yes the transom is 20" on the money, I haven't check the motor shaft? Yet.


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## tom_in_orl (Dec 9, 2006)

I agree with Tom _C. Just a clarification. With a 20" transom and a 20" shaft mounting the jack plate 3" up is a good starting point *as long as the jack plate is in the center of its adjustment range*. By that I mean you can go and down and equal amount.


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## Tsport (Jan 4, 2007)

Thanks for the input. 
That would give me 1.5" up or down. So with 3" of jackplate travel the lowest I could go would be 1.5" above the existing transom and the highest I could go would be 4.5" above the existing transom. Sounds good to me but I have never used a jackplate before.


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## Brett (Jul 16, 2008)

previous post

http://www.microskiff.com/cgi-bin/yabb2/YaBB.pl?num=1235777190


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## Tsport (Jan 4, 2007)

Thanks Brett, I seen that post it just wasn't clear of a good starting point. BTW your link in that post for Dillon's Racing is what I used. After reading it and then seeing that I had most of the material in hand, mainly the alum. stock I put it to good use. Just finished it today.

Thanks!


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## Brett (Jul 16, 2008)

Tilt the bow of your boat up 5 degrees from horizontal while on the trailer.
Set your jackplate to the middle of it's range
And when a level is set from the bottom of your transom
it should intersect the lower unit just above the top of the water inlet.
Make sense?
Boats don't run level on plane. they run bow high, on average 5 degrees high.


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## Tom_C (Dec 10, 2006)

> I agree with Tom _C. Just a clarification. With a 20" transom and a 20" shaft mounting the jack plate 3" up is a good starting point *as long as the jack plate is in the center of its adjustment range*. By that I mean you can go and down and equal amount.


Nope, 

Let me clarify, 99% of the boats I work with have transoms for 15" motors. 

With a 15" motor the distance between where the motor sits on the transom and the cavitation plate is 16.5". 

I had not seen a boat with a 15" transom. A Gheenoe Highsider 13, and 15-4, and Gheenoe Classic 15-6 have a 17" transom. ECC’s Gladesmen, Gordon’s Ambush both have 18 inch transom and Gheenoe LT setup for a 15" motor has a 18.5" transom. All of these boats will run great with a stock prop with the top of the jack plate 19" above the bottom of the transom.

So knowing this what I am saying is with a 20" motor on a 20" transom mounting the top of the jack plate 3" above the transom would be the same as mounting a 15" motor on a jack plate with the top of the jack plate set at 18". 

With that said lets look at it this way. You have a 20" motor, ifthe distance between where the motor sits on the transom and the cavitation plate is 21.5", then mounting your jack plate up 3 inches your cavitation plate will be 1.5" above the bottom of the transom. With a 6" jack plate you should be able to raise your motor 2" more with no problem.


but this is just my opinion


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## Tsport (Jan 4, 2007)

> > So knowing this what I am saying is with a 20" motor on a 20" transom mounting the top of the jack plate 3" above the transom would be the same as mounting a 15" motor on a jack plate with the top of the jack plate set at 18".
> >
> > With that said lets look at it this way. You have a 20" motor, ifthe distance between where the motor sits on the transom and the cavitation plate is 21.5", then mounting your jack plate up 3 inches your cavitation plate will be 1.5" above the bottom of the transom. With a 6" jack plate you should be able to raise your motor 2" more with no problem.
> > [/size]
> ...


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## tom_in_orl (Dec 9, 2006)

Good thread and great clarification by Tom_C. 

[smiley=bravo.gif]


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## Tsport (Jan 4, 2007)

Thanks to all for the great info. I mounted it 2" above the existing transom which should provide plenty of adjustment. I was worried about my steering cable but it worked out with re-routing it.

here are a few pics of my home made jackplate.


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