# Jack Plate "Setback" Transom Question



## T Bone (Jul 24, 2014)

I am thinking about adding a jack plate to my skiff. The goal is to be able to run shallower with a little better performance. I fish the Nature Coast and these winter tides can really make navigating a pain. My current skiff is Skull Island 16 with a 2007 Yamaha 25hp two-stroke (15" shaft with manual t/t). I would probably add an Atlas Micro Jacker due to the minimal set back. 

The concerns i have about adding a jack plate are due to the Skull Islands "setback" transom. Here is an older picture of my skiff to show the "setback" transom. 
 
What are the negatives of too much set back? How much set back would be considered too much? Would adding a jack plate allow me run significantly shallower without a tunnel?

I am not a naval architect by any means. Any comments, recommendations, etc. are welcome.

Thanks,
T


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## Smackdaddy53 (Dec 31, 2012)

If you add a bunch of setback and jack the motor up you’ll want a compression plate and a prop with more cup so it’s not blowing out. 4” of setback isn’t going to allow you much more shallow water ability, the general rule of thumb is for every 12” of setback you gain 1” to raise the motor.


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## Vertigo (Jun 3, 2012)

Adding a jack plate just to raise the motor a few inches (or less) is not necessarily a good idea when navigating the Nature Coast. Limestone rock and oyster bars hidden randomly just below the surface make knowing where you're going far more important than running a few inches more shallow when on plane. 

When exploring new territory at idle speed, tilting the motor will work almost as well as using a jack plate. On plane, jack plate or not, you'd better stick to known routes.


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## SomaliPirate (Feb 5, 2016)

Vertigo said:


> Adding a jack plate just to raise the motor a few inches (or less) is not necessarily a good idea when navigating the Nature Coast. Limestone rock and oyster bars hidden randomly just below the surface make knowing where you're going far more important than running a few inches more shallow when on plane.
> 
> When exploring new territory at idle speed, tilting the motor will work almost as well as using a jack plate. On plane, jack plate or not, you'd better stick to known routes.


I agree. You can get away with running super skinny around cedar key, but anything around CR or Ozello gets sketchy.


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## T Bone (Jul 24, 2014)

Vertigo said:


> Adding a jack plate just to raise the motor a few inches (or less) is not necessarily a good idea when navigating the Nature Coast. Limestone rock and oyster bars hidden randomly just below the surface make knowing where you're going far more important than running a few inches more shallow when on plane.
> 
> When exploring new territory at idle speed, tilting the motor will work almost as well as using a jack plate. On plane, jack plate or not, you'd better stick to known routes.





SomaliPirate said:


> I agree. You can get away with running super skinny around cedar key, but anything around CR or Ozello gets sketchy.


I appreciate the advice. My family has had a place along the nature coast for over 40 years and we have been operating boats over there the whole time... I am just looking for advice on adding a jack plate to a skiff that already has setback.


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## Smackdaddy53 (Dec 31, 2012)

Vertigo said:


> Adding a jack plate just to raise the motor a few inches (or less) is not necessarily a good idea when navigating the Nature Coast. Limestone rock and oyster bars hidden randomly just below the surface make knowing where you're going far more important than running a few inches more shallow when on plane.
> 
> When exploring new territory at idle speed, tilting the motor will work almost as well as using a jack plate. On plane, jack plate or not, you'd better stick to known routes.


I never understood this way of thinking. I get that knowing where you’re going is key but if you want to keep from hitting obstructions, seagrass beds, oyster shell, rocks etc with your lower unit why is raising the motor going to cause you to hit bottom or get you in a bind? 
I see guys with non tunnels scoffing at the idea of running a tunnel because “they don’t need one” but their lower unit looks like they drug the skeg off on the boat ramp because they are constantly trenching bottom trying to run skinny. It’s comical. There are lots of guys on here that run non tunnels and outfitted their motor with Foreman props, compression plates and low water pickups to get the motor a few inches higher and it worked great. It all depends on the hull and I don’t think adding another 23 pound jackplate (Atlas MicroJacker) on a small hull with a 25hp is going to really add much shallow running ability, it might actually cancel itself out adding that weight on the transom and moving the weight of the motor even further back.


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## T Bone (Jul 24, 2014)

Smackdaddy53 said:


> I never understood this way of thinking. I get that knowing where you’re going is key but if you want to keep from hitting obstructions, seagrass beds, oyster shell, rocks etc with your lower unit why is raising the motor going to cause you to hit bottom or get you in a bind?
> I see guys with non tunnels scoffing at the idea of running a tunnel because “they don’t need one” but their lower unit looks like they drug the skeg off on the boat ramp because they are constantly trenching bottom trying to run skinny. It’s comical. There are lots of guys on here that run non tunnels and outfitted their motor with Foreman props, compression plates and low water pickups to get the motor a few inches higher and it worked great. It all depends on the hull and I don’t think adding another 23 pound jackplate (Atlas MicroJacker) on a small hull with a 25hp is going to really add much shallow running ability, it might actually cancel itself out adding that weight on the transom and moving the weight of the motor even further back.


And that is part of my question... would the additional setback offset the ability to raise the motor and run shallower?

Even if i could raise the motor 1" without blowing out, that would be a bonus in my eyes. I dont think the additional 23lbs will hurt. The motor weighs 105lbs so even with the jack plate weight, it is less then the motor the boat comes standard with.

Also, the idling ability of a motor jacked up vs trimmed up is pretty substantial in my experience. Only using the trim while idling over shallow bottom actually pushes the stern down.

I am not trying to have zero skeg below the hull while running. I get it, my boat doesnt have a tunnel. I was just curious if, with the design of the transom on my skiff, would adding a jack plate allow me to raise the motor a few inches (or less) or would the 4" setback of the jack plate plus the 6-8" of setback incorporated into the transom be too much setback?


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## Smackdaddy53 (Dec 31, 2012)

Can you take a photo with the motor down and in the trimmed flat position so we can see where the cav plate is in relation to the hull bottom? Try to take the photo so we can see the side and rear view looking level with the bottom of the hull. 
I have no experience with these hulls. Have you asked the shop that builds them?


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## T Bone (Jul 24, 2014)

Smackdaddy53 said:


> Can you take a photo with the motor down and in the trimmed flat position so we can see where the cav plate is in relation to the hull bottom? Try to take the photo so we can see the side and rear view looking level with the bottom of the hull.
> I have no experience with these hulls. Have you asked the shop that builds them?


I will get a photo up here soon. And yes i contacted the builder and they have never put a jack plate on one of their skiffs (i believe they've only built 20 or so skiffs and are located in SE FL where running shallow isn't really a priority)


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## Smackdaddy53 (Dec 31, 2012)

T Bone said:


> I will get a photo up here soon. And yes i contacted the builder and they have never put a jack plate on one of their skiffs (i believe they've only built 20 or so skiffs and are located in SE FL where running shallow isn't really a priority)


A cheaper and lighter option that may work would be to add a static jackplate and experiment with motor height and setback that way.


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## SomaliPirate (Feb 5, 2016)

T Bone said:


> I appreciate the advice. My family has had a place along the nature coast for over 40 years and we have been operating boats over there the whole time... I am just looking for advice on adding a jack plate to a skiff that already has setback.


You know better than me then! I mostly fish CK.


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## Vertigo (Jun 3, 2012)

T Bone said:


> I appreciate the advice. My family has had a place along the nature coast for over 40 years and we have been operating boats over there the whole time... I am just looking for advice on adding a jack plate to a skiff that already has setback.


As far as adding a jack plate to a flat bottomed skiff with a setback transom, I don't think the changes it would make would justify the cost and hassle, particularly around the Nature Coast, but most anywhere else too.


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## ZaneD (Feb 28, 2017)

Adding any jack plate (manual or hydraulic) is typically going to give you 2"+ of setback and raise the motor by about 1-2" just because of how it bolts to the JP. In your situation it is unlikely that you'll be able to raise more than another 1-2" inches before the prop blows out. In short, I think a manual (static) JP is the best option because it'll give you that extra 2" or so of running depth without excess weight and cost.


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## T Bone (Jul 24, 2014)

Smackdaddy53 said:


> Can you take a photo with the motor down and in the trimmed flat position so we can see where the cav plate is in relation to the hull bottom? Try to take the photo so we can see the side and rear view looking level with the bottom of the hull.
> I have no experience with these hulls. Have you asked the shop that builds them?


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## Smackdaddy53 (Dec 31, 2012)

I bet if you added a compression plate you could come up another 1”, maybe 2”.


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## T Bone (Jul 24, 2014)

Smackdaddy53 said:


> I bet if you added a compression plate you could come up another 1”, maybe 2”.


What would be the best way to achieve this 1"-2"?


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## crboggs (Mar 30, 2015)

Is it possible to hang a shorter shaft motor on there?


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## T Bone (Jul 24, 2014)

crboggs said:


> Is it possible to hang a shorter shaft motor on there?


It is the short shaft (15") model


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## zthomas (Jan 14, 2014)

Have to agree that a hydraulic jack plate probably isn't going to make enough of a difference to justify the cost and the extra stuff to break.

Just glancing at your photos, I'd be surprised if you couldn't raise your motor an inch or maybe two. Switch to a 4-blade and/or something with more cup and possibly add a plate, but I suspect that's not necessary.

I have a tunnel but agonized over the same question. I started experimenting with motor height and props and was able to raise the motor two holes (1.5") with virtually no ill effects. In the end, I decided the additional improvement I'd see in running draft with the jackplate wasn't worth even a small increase in poling draft — not even considering the expense and the added complexity.

It looks like your motor has only one set of bolt holes though, so I guess raising it would require either drilling new holes or adding a manual plate. I didn't know the smaller hp engines didn't have holes to adjust height.


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## Smackdaddy53 (Dec 31, 2012)

T Bone said:


> What would be the best way to achieve this 1"-2"?


As others stated I did not realize your motor only has one set of mounting holes so you may try a set of setback c channels like they sell at Bob’s Machine Shop.


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## Capnredfish (Feb 1, 2012)

I agree with Smack. Fixed mount or maybe a manual jackplate for your low water season.


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## Rick hambric (Jun 24, 2017)

Manuel jack is the way to go for a skiff like that. Biggest concern would be moving the CG with a 4in jack. Moving the motor further away from the transom will move the cg back. So you will increase draft by probably 1/2”, but my concern would be at high speed, with additional setback there is always the chance of creating a porpoise problem. As the motor moves back, the more leverage it can produce. If your prop cannot maintain grip then it will give you the wonderful lift and fall motion we all love. Have you contacted the manufacturer to see if they’ve done one with a jack and what was the end result? A phone call can save a lot of headache and $$.


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## hipshot (Sep 29, 2018)

T Bone brought up exactly the reason I am having a jack plate installed on The Skull Island I have being built. I do a lot of idling in shallow water, and I am almost always in the wind. I've found that raising the outboard and having it much closer to vertical gives me a whole lot more control in the wind, as opposed to having the outboard tilted way up with the prop aimed down at a steep angle. 

I'm not looking to run shallower on plane. I'm looking to idle shallower with more control.

And yes, I speak from experience, not from my imagination. The folks at Skull Island do not recommend jack plates, but they understand my rationale for requesting one. I discussed the issue with a friend who owns a Skull Island a while back. He told me that he initially discarded the idea, but after running his skiff for a couple of years he says he is dangerously close to installing one.

Anyway, right or wrong, I'll have one on my new Skull Island Skiff when I pick it up.


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## gbc11 (Oct 4, 2018)

Since you know what you want. Will it cost you performance in speed and draft more then likely. Now saying that. With what your asking, I can see adding a jack plate or riser plate to get the motor up. For moving in shallow water. You’ll probably need a cav plate, cupped 4 blade and maybe a low water pick up. The short answer is it’s your boat make it perform how you need it to.


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## richg99 (Nov 28, 2009)

hipshot, So, when will we get to see that new boat?


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## tdlredbud (Jan 13, 2016)

T Bone said:


> I am thinking about adding a jack plate to my skiff. The goal is to be able to run shallower with a little better performance. I fish the Nature Coast and these winter tides can really make navigating a pain. My current skiff is Skull Island 16 with a 2007 Yamaha 25hp two-stroke (15" shaft with manual t/t). I would probably add an Atlas Micro Jacker due to the minimal set back.
> 
> The concerns i have about adding a jack plate are due to the Skull Islands "setback" transom. Here is an older picture of my skiff to show the "setback" transom.
> 
> ...


I had a center console 16 skull island with a Honda 30 hp on it. Great boat. I put a Bob,s mini on it and it made quite a bit of difference.


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## hipshot (Sep 29, 2018)

richg99 said:


> hipshot, So, when will we get to see that new boat?


Not sure yet. The original date was mid December, but I was told that they may run a little bit later now.


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