Mini-Jacker question

[reelfishin]

I've been debating on whether or not to adapt a good running long shaft 25 hp motor I have to my 15" transom boat.
While I know I can make a home made adjustable bracket, I like the idea of a one piece adapter.
What I can't figure out is why they make the Mini-Jacker a 3" rise not a 5" rise?
If I'm trying to mimic a 20" transom, wouldn't I want to put my motor up an addition 5" or to the point where the anti cavitation plate is just above the bottom of the boat?
I could mount the Mini Jacker just above the top edge of the transom but that looks wrong even though the motor height is correct.
I will no doubt probably just make my own bracket using 4" aluminum angle and some stainless bolts, but was wondering if I'm missing something here?

 

[tashasdaddy]

Re: Mini-Jacker question

look at my jack plates and transom elevators. easy solution.

 

[Shockley]

Re: Mini-Jacker question

Tashasdaddy, can you repost your jackplates? I am having trouble finding them.

 

[Willyclay]

Re: Mini-Jacker question

FYI: http://www.dillon-racing.com/jackplate/index.htm

 

[reelfishin]

Re: Mini-Jacker question

Good link, that's nearly identical to what I was planning on doing only I intend to just make it ajust in inch increments.

I still don't see why the Mini Jacker is a 3" lift?

 

[tashasdaddy]

Re: Mini-Jacker question

my jack plate, http://forums.iboats.com/showthread.php?t=321432&highlight=jack+plate

 

[Whoopbass]

Re: Mini-Jacker question

I recently made the jack plate in the link that Willyclay posted.

I needed almost a 6" rise for jet drive then when I switch back to prop I need to drop it back down level with the transom.
It was fairly easy to make with the exception of the adjustment slots. I used a hack saw but it wasn't cutting that straight and with the angle of the blade it was taking forever to cut.
I ended up buying a Dremel tool and used the small cutting wheels to cut the slots. The wheel was not big enough to cut all the way through so I finished it up with the hacksaw. A file cleaned it up pretty good.
The only way I could get the Dremel with the wheel to work was to clamp a straight edge to the aluminum angle and use it as a guide/fence otherwise the cutting wheels would break.
Be very careful not to cut the slots to big or else the carriage bolts will have alot of slop. Smaller is better and then use the file to shave it down.

For your situation Tashasdaddy's design would probably work better.

 

[Frank Acampora]

Re: Mini-Jacker question

Reasaon: Because the mini jacker was not designed to adapt a 20 inch engine to a 15 inch transom. It was designed to raise an engine to the best height above the hull bottom for maximum performance. Most applications in quest of performance using the mini will not need more than 3 inches of lift.

 

[Shockley]

Re: Mini-Jacker question

On the plywood used between the jacks, is there a special coating needed? Will marine paint do? Also, do you directly mount the upper mounting bolts to the jacks directly and the lower in the ply? Is there another piece of angle used on the bottom to bolt through? Just wondering because I leave for the lake on Thursady and am trying to get up and running in a hurry. Thanks!

 

[reelfishin]

Re: Mini-Jacker question

Reasaon: Because the mini jacker was not designed to adapt a 20 inch engine to a 15 inch transom. It was designed to raise an engine to the best height above the hull bottom for maximum performance. Most applications in quest of performance using the mini will not need more than 3 inches of lift.

I was thinking the same thing till I went back and read their main ad:

"This cast aluminum offset type jack plate is designed for clamp-on mount outboard motors up to 35 HP. The Mini-Jacker? allows mounting of long shaft motors to shorter shaft transom boats. The mini-jacker? stands off transom 4". The engine mounting surface is 11 1/2" wide x 10" high and features a vertical offset of 3". The overall width of transom mounting flanges is 17".

(http://www.thmarine.com/product.cfm?PRID=23)

In my eyes, if it's only offsetting the motor 4" and up 3", then how is it going to make up for a 5" average difference in shaft lengths?

The only way to make one work would be to mount it partially above the transom on the front side, which just don't look as strong to me.

I like the one piece cast aluminum construction, but would never want a plate mounted only at the top of my transom.

What I am thinking of doing, it making the jack plate wide enough to match the spacing on the inner knee braces on the hull, then bolt through both outer knee brace flanges to help transfer the added stress directly to the braces vs. the flat part of the transom. It would mean making the plate about 3" wider than needed overall. I would also back the wood with aluminum plate to prevent wear. A jack plate will also gain me a bit of room at the transom as is with the motor mounted direct on the transom, the cables, handle, and motor pan intrude a lot on the boat's space.

What I was wondering is if since the Mini Jacker puts the motor back 4", are they assuming that the motor can then run 2" shallower being it's in supposedly cleaner water? I wouldn't think that would make much difference on such a small boat or motor?

 

[BWR1953]

Re: Mini-Jacker question

...What I was wondering is if since the Mini Jacker puts the motor back 4", are they assuming that the motor can then run 2" shallower being it's in supposedly cleaner water? I wouldn't think that would make much difference on such a small boat or motor?

So what did you end up doing? Got pix of the end result?

I'm looking at a mini-jacker plate right now for my Sea Nymph Fishing Machine. There's a used one for sale cheap on C/L and I'm mightily tempted.

From what I've read of jackplates, I think when they say "cleaner" water, that they also mean deeper water. That is, as the water passes to the rear of the transom of the boat, past the jackplate setback, the water "rises" several inches. Therefore, even though the engine is mounted higher and the prop is above the bottom of the boat, it is riding fully submerged while under way. See drawing below.

 

[reelfishin]

Re: Mini-Jacker question

I don't think that the small amount that the mini jacker moves the motor back and upward is enough to really make much of a difference. For now I continue to run my short shaft 20 hp. I figure that if I wanted to get clean water and to run my long shaft 25, I'd be better off just moving it up with as little rear offset as possible for both transom load reasons and for performance. I suppose that if I were going the other direction, a 15" motor on a 20" transom, if I were to move the motor rearward about 8" or more, I could mount it at the 15" transom height to find clean water. But the mini jacker don't move the motor back that far and in my case, it would have to be mounted an inch or more above the transom to get the right height. I passed on the mini jacker for now, I'll most likely just make my own or keep searching for a 15" motor. For now, the 20 hp is doing OK.

 

[BWR1953]

Re: Mini-Jacker question

I don't think that the small amount that the mini jacker moves the motor back and upward is enough to really make much of a difference. For now I continue to run my short shaft 20 hp. I figure that if I wanted to get clean water and to run my long shaft 25, I'd be better off just moving it up with as little rear offset as possible for both transom load reasons and for performance. I suppose that if I were going the other direction, a 15" motor on a 20" transom, if I were to move the motor rearward about 8" or more, I could mount it at the 15" transom height to find clean water. But the mini jacker don't move the motor back that far and in my case, it would have to be mounted an inch or more above the transom to get the right height. I passed on the mini jacker for now, I'll most likely just make my own or keep searching for a 15" motor. For now, the 20 hp is doing OK.

Thanks for the reply. My boat is rated for 35hp but is currently rigged with a 25hp motor without power trim and tilt. The anti-ventilation plate is actually about 1 1/2 inches below the bottom of the keel, but the boat runs well enough, so I won't change the 25hp configuration at all.

At some point, I do plan to upgrade to a 35hp motor with power trim and tilt, so am thinking of adding the mini-jacker at that time. If I can pick up the jackplate now for $35 - 50 or so, then it'd be worth it in the long run, when I make the 40% power upgrade.

I will be running in some very skinny water, so want as much lift as I can get.

 

[wizbang 13]

Re: Mini-Jacker question

Take a look at "Panther 55 trim /tilt" Get that plate OUT of the water at high speed

 

[BWR1953]

Re: Mini-Jacker question

Take a look at "Panther 55 trim /tilt" Get that plate OUT of the water at high speed

Jackplates are always out of the water at any speed. Are you thinking of a hydrofoil?

I checked out the Panther... way too expensive.

 

[crackedglass]

Re: Mini-Jacker question

If he's working on a smaller boat, some of those add on jack plates are quite heavy, the mini jacker is probably the only store bought option aside from fabricating one yourself.

I've made up a few jack plates, usually even with a minimum setback, you need more than the 5" difference in the two motor shaft lengths to get the right motor height. I've been able to raise the anticavitation plate an extra inch, sometimes two, when setting the motor back on a jack plate. Which this in mind, if using a 20" shaft motor on a 15" transom, the jack plate needs to raise the motor as much as 6 or 7" on some boats. While it would run just fine raised up 5" I'd not want to run it any deeper.

The mini jacker would work well to mount a kicker motor off to one side on a shallow v hull boat when used to simply raise the motor to gain proper height but there are other options for that application as well.

I measured several smaller motors I have here, most 15" sized motors seem to measure an actual 17 to 17.5", while most 20" motors ranged from 19" to 22 1/2" long. If you had one of the longer motors, (the one I measured was a 30hp Evinrude from about 1986), I could see proper mounting being out of the range of the mini jacker plate altogether.

 

[BWR1953]

Re: Mini-Jacker question

Well, I missed out on the mini-jacker that I was following. He did drop the price to just $35, with only two offers... mine being second fiddle! Dangit!

Next time...

 

[freeisforme]

Re: Mini-Jacker question

I bought a boat a while back with one of those Mini Jacker plates as part of the deal, the boat had a 15" transom, the motor it came with was for a 20" transom. If I were to have used the Mini Jacker plate with the 20" shaft motor on that boat I'd have had to mount the thing nearly 3" above the transom. The amount of rise it gives is no way near enough to make a 20" motor work on a 15" transom. I sold the thing and made my one from aluminum angle iron and wood.
I'm not sure who engineered the Mini Jacker but it looks like someone didn't know much about boats in the real world. It don't set the motor back enough to be concerced about clean water or raising the anticav plate higher than the keel, and if mounted high enough on the transom to make up the 5" difference, putting the anticav plate just a bit higher than the keel, you have only a portion of the plate supported. I was also not a fan of having to drill odd pattern holes in a new transom which would, (in the event I found a short shaft motor), not match up with any motor sans the plate.

Forget the Mini Jacker, make your one adapter. You'll save yourself a chunk of change and end up with a better solution in the end. When I made my plate, I made the plate bolt up to the same bolt pattern as my motor would use, with the thinking that if one day I come across a short shaft version of that motor, it will bolt right up to the same holes, and I won't regret having drilled another set of holes in my transom.

 

[ddrieck]

Re: Mini-Jacker question

You can gain the 5'' you need by using this vertical extension plate. I have helped many with the same problem your having. Send me a PM if your interested

 

[freeisforme]

Re: Mini-Jacker question

I already made my own out of 2" aluminum angle mounted so as to be adjustable. I drilled holes in 1" increments and used four stainless bolts and washers to adjust the height. I can raise or lower the motor in 1" steps this way. I laminated two pieces or 3/4" ply with a layer of .040" aluminum folded over the top and down the rear to protect the wood. I bolted the home made jack plate to a set of bolt holes which would correspond to the largest motor I can run, with the thinking that if I was to find the perfect motor, I could remove the jack plate and bolt up the motor. Right now I have a clamp on Mercury 25hp on it. The plate can also be lowered back down to still run a short shaft motor if I need to, and sets back just enough to clear the clamps.

What I built was basically just a copy of a manufactured jack plate only smaller. Since I laminated the wood in epoxy and glass, plus the aluminum skin, it will no doubt out last the boat.

I thought about making it with a self adjusting screw so I could just loosen, lift and retighten at a new height but felt keeping the weight down was more important on a small aluminum boat.