Help please.. Bob's Machine Shop Mini Jack Plate

I got a Bob's Machine Shop Mini Jack Plate that Im gonna put on my 1448 with a 25hp Evinrude. I was wondering, being that there are three settings for horizontal movement, if I could get some guidance on where to set it. I know there are a few river runners on here that deal with jack plates all the time, and I could really use the help. Im planning on putting it on this weekend, and its not adjustable while on the water, so Im looking for a good starting point. Im looking for the best top end speed.

Here is the link:
https://www.bobsmachine.com/Products/jackplate_mini-MMJ.cfm

Thanks guys..

I made an adjustable jackplate for my boat. I run a 25hp Evinrude. I have mine set up about 1" higher then the top of the transom.
I don't think its made a bit of difference in performance. The only thing is that I have to reach back further to operate it.
I would seriously consider returning it if you bought it for performance. However your boat might be different then mine and you will see something. I have a decked 15' semi v Gregor.

I'd set it up with the cavitation plate even with the bottom of the boat,but where you could set it higher if wanted too.Less lower in water = speed & shallower water you can go in.

crazymanme2 said:

I'd set it up with the cavitation plate even with the bottom of the boat,but where you could set it higher if wanted too.Less lower in water = speed & shallower water you can go in.

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Thanks. How would you set the horizontal movement though? It has 3 settings; 4-1/4" setback, 5" setback, and 6-1/8" setback. Is it the further back the better?

Most jack plates that I've seen adjust up & down.If you have different set backs I guess I'd start in the middle.The farther back you put your motor it will bring the bow up & also allow cleaner water for your prop.If you have issues with the tiller put it on the closest setting.Also the minus, the farther back you put it the farther down your boat will sit in the water while not underway.The jackplate becomes a lever.Either way it's all adjustable.

I've had both hydraulic and manual jackplates. I have a manual on my Caro Skiff now. The "normal" rule of thumb is " for every two inches BACK...you can raise the engine one inch".

We do it down here in the TX flats to gain shallow running capability. The farther back, the "cleaner" the water is, so they say. Bass boat guys do it to gain speed. I can't help there.

I'd start in the middle setting and see, but do not starve your engine for water cooling. Watch the "p@sser stream". Rich

What series of 25 do you have to begin with? If you have through-hub exhaust you can raise that engine more than you can the older non through-hub style due to water pick-up and propeller design. On the set back distances one thing to remember here is that the farther back you go the longer you have to reach to shift the engine if it is not a remote controlled engine! Second, the length of set-back depends on what the boat needs. If it is bow heavy and you have trouble lifting the bow with engine trim (in and out) then go back farther, if that is not an issue then stick with the closest setting. If you are running a through-hub engine and the prop is in good shape then start with the cavitation plate 1-1.5 inches above the bottom of the boat. This is measured with the cavitation plate parallel with the bottom of the boat, not trimmed in or trimmed out. Take a straght edge and either put it on the bottom of the cav plate and move it forward to the hull and measure or put it on the bottom of the boat and bring it back under the cav plate and measure the difference. You should do quite well with this initial setting. No issues with cooling will occur. Now, the way to tell if you can go higher is to make sure your prop is hooked up at the initial setting and the boat planes off with minimal ventilation or none. If this is the case then go up another inch (2 to 2.5" total) and try it there. That will probably be somewhere close to the max you can go in your case. You should gain both RPM and a little speed along the way. If you are ventilating at the higher settings and your WOT RPM is on the high side (and the boat didn't speed up) then you either have to go back down some or take the prop to a prop shop and have it cupped. Along with the normal trailing edge cup have them bring the cup around the leading edge a little farther than they normally do. Usually this point is the point farthest from the centerline of the hub. Tell them what you are doing and they will work with you.

Thanks guys. Thats the info I was looking for. Love this forum Its a thru hub exhaust 1992 evinrude on a 1448, and the setback is the reason I want to put the jack plate on to begin with. Since I put on the larger motor, my tiller handle hits my seat. Raising it up a few inches and setting it back around 4" would be ideal for comfortable steering. I really dont need the speed, but ill take it. Ive just had that jack plat sitting in the shop for a while now and thought I would put it to good use.

Im hitting 30mph now by myself, and Im adding this jack plate so i hope to see a couple more mph. I also just ordered a 35hp carb, intake, and throttle cam off ebay. My goal is to be able to go 30mph with 2 people in the boat, and somewhere around 35mph by myself.

Thanks again guys.