Jacking plate

[Seapup]

Just had another thought ..... Is a 12" jacking Plate going to effect my tow ball weight by much?

Someone could probably throw the numbers of a 12" change and 200lb outboard in a calculator for you. My 410lb df90 was on a jackplate and single axle stock trailer.

If you get a jackplate look at ones that also let you set the trim angle similar to wedges to give a larger trim down range. As long as the prop clears the water you have more cowl room and less trim time when tilting up. I think my final jackplate I set with about 20 deg tilt. You can see the angle of the mounting board compared to the transom here:



With a 12" setback the arm connecting the rudders to the motor is on an almost 45 deg angle vs parallel to the rudder tie bar. You can see the angle in gazmn's picture. The greater the angle the less the motor will turn if the cable connects to the rudders first. Mounting the cable to the motor first then the rudders allows full travel of both. I don't know if this is a possibility on an M.

This pic (12" setback) shows the steering cable to the motor for full range of motion and tie bar angle.



The further back you go the higher the motor needs to be for efficiency as the boat "squats" above about 5mph. Its slightly more likely to cavitate bouncing in short steep waves too. I had 3x 20" shaft motors, the transom mounted bf50 was about 1" above the transom, the 5" setback required about 3" of rise, and the 12" required about 5" of rise to operate similarly. The higher you raise the motor the more likely the connecting bar is to bind when the motor is tilted up vs down as the geometry changes. With the motor down the tie bar is angled up and as the motor tilts up the connection point comes down.

IMO If you are building a deck to utilize the space go with a 12" setback, otherwise I would keep it simple and go with very little setback. I personally don't think they add any motoring performance to an X, maybe even take some away. They do give you a larger boat with easier access and ability to swap motors a little easier.

[Tomfoolery]

Just had another thought ..... Is a 12" jacking Plate going to effect my tow ball weight by much?

Someone could probably throw the numbers of a 12" change and 200lb outboard in a calculator for you. My 410lb df90 was on a jackplate and single axle stock trailer.

I get a rather imprecise 10 lb difference, plus or minus a couple of pounds, from moving a 200 lb blob on the stern back another 12". That's based on a crude sketch of the boat and trailer geometry I had laying around. But not enough to worry about; tossing a couple more items into the v-berth would negate the effects at the hitch ball. At least the vertical effects.

[Jimmyt]

I was using 600 lbs and the dimensions off my 2013 rig w/stock alum trailer - single axle. Had no idea what the motor weighed - just threw out a number I thought would cover it. Looks like my Etec actually weighs in the neighborhood of 240 lbs. Using that weight and my dimensions, I get 12 lbs lighter tongue weight for a 12" rearward shift - which agrees with Tom's numbers, and as he points out is nothing to worry about. Man, I thought those motors were heavier. Also, the manual shows one weight for the 40, 50, and 60. Interesting...

[Neo]

I went out there with a ruler in hand yesterday to gauge the impact of having the OB 12" back ...... Man you could mount a whole swim platform (and diving board!) in that distance
I've decided 12" is just too much (and too expensive) for me so I'm looking at something smaller. Will update you on what I get

All the best.
Neo

[Herschel]

I personally don't think they add any motoring performance to an X, maybe even take some away.

I thought that increased performance was the main reason for using a jack plate. That was certainly my experience. I got an extra 1-2 knots speed with probable increase in fuel efficiency. Definitely no worse performance that I can see. I am curious why you think there could be a downside.

[Gazmn]

When I installed one on my I went with a 10" setback I believe






If I were to do it on my I would go with one of these I,d get mid size one with the small swim platform
http://www.armstrongnautical.com/brackets.htm

https://www.youtube.com/watch?v=mvcksCz0OBM

I just figure if I was gonna spend the money might as well do it right & with the movin that eng back plus a swim platform is the only way to go just sayin thats all

J

I'm borrowing from John's entry. 1- Cause he's Da Man & 2. - Cause I can
I have the same jackplate

+1 on what Herschel said regarding more gains than loss.

But John's pic helps to make my point. If you keep your boat In the water, slipped or moored, Prime & PROPERLY X2 Bottom paint your jackplate - no matter the size

I can't stress this enough unless you want to buy x2 or screwup your other galvanics in the water. I learned this the hard way. While I didn't buy another JP, mine won't budge for nothin'
& had to make final adjustments for a re repower by moving the motor up & down by installation holes

[Highlander]

Mmm That,s a good point !!

J

[Seapup]

I thought that increased performance was the main reason for using a jack plate. That was certainly my experience. I got an extra 1-2 knots speed with probable increase in fuel efficiency. Definitely no worse performance that I can see. I am curious why you think there could be a downside.

My statement was meant to express large setback vs short, not jackplate/none.

If your motor is the wrong height a jackplate can fix that. My opinion is once at the correct height a mac does not see extra performance from setting the motor further behind the stern since it does not level out perfect on top the water like a speedboat.

The rationale for setback on a speedboat is you can raise the motor more the further back it is (rides in stern wake). The trim should be able to be set more neutral with less drag since prop is pushing more from behind the hull in the stern wake vs a prop on a lever below the hull and trim correcting. The theory is used to squeeze top speed out of planing boats.

A mac is generally bow up under power, especially below 25mph. A greater setback distance will add more drag by putting the lower end deeper under power while the boat is angled. If you use a hydrofoil or prop trim to force the bow down past is natural ride position more drag is added too.

The other downside of larger setback is changes in boat angle magnify the prop depth exponentially. Short steep waves raise and lower the motor more than a motor on the transom, similar to an outboard hanging back off the stern of a traditional sailboat.

If I were to do it on my I would go with one of these I,d get mid size one with the small swim platform
http://www.armstrongnautical.com/brackets.htm

A full platform was always on my want list. Room was my ultimate end goal when switching motors & jack plates the last time. I almost bought a clean used 25" df140 to replace the DF90 with plans to jack it way up till someone talked some sense to me When I reevaluated I decided I used the space every outing and only high speed occasionally. When I swapped motors I bought composite Trex with plans to toss my wood deck and build a composite one extending over the rudders the full width of the transom, just never got around to it.

[Neo]

My 5" Jacking plate arrive soon but I can't figure out how to do the steering linkage ... if your solution works well can you please post up some pictures please

[Herschel]

My 5" Jacking plate arrive soon but I can't figure out how to do the steering linkage ... if your solution works well can you please post up some pictures please

I will need a few days to get up to my boat (it is 45 minutes away), but it is an "X". Not sure about how similar the steering linkages are between the "X" and the "M", but I'll be glad to take some pictures and post them in a few days.

[Neo]

Many thanks for your kind offer Herschel but It's probably best I see a solution on a 26M as the pit area is very different to a 26X

All the best.
Neo

[Highlander]

I thought that increased performance was the main reason for using a jack plate. That was certainly my experience. I got an extra 1-2 knots speed with probable increase in fuel efficiency. Definitely no worse performance that I can see. I am curious why you think there could be a downside.

My statement was meant to express large setback vs short, not jackplate/none.

If your motor is the wrong height a jackplate can fix that. My opinion is once at the correct height a mac does not see extra performance from setting the motor further behind the stern since it does not level out perfect on top the water like a speedboat.

The rationale for setback on a speedboat is you can raise the motor more the further back it is (rides in stern wake). The trim should be able to be set more neutral with less drag since prop is pushing more from behind the hull in the stern wake vs a prop on a lever below the hull and trim correcting. The theory is used to squeeze top speed out of planing boats.

A mac is generally bow up under power, especially below 25mph. A greater setback distance will add more drag by putting the lower end deeper under power while the boat is angled. If you use a hydrofoil or prop trim to force the bow down past is natural ride position more drag is added too.

The other downside of larger setback is changes in boat angle magnify the prop depth exponentially. Short steep waves raise and lower the motor more than a motor on the transom, similar to an outboard hanging back off the stern of a traditional sailboat.

If I were to do it on my I would go with one of these I,d get mid size one with the small swim platform
http://www.armstrongnautical.com/brackets.htm

A full platform was always on my want list. Room was my ultimate end goal when switching motors & jack plates the last time. I almost bought a clean used 25" df140 to replace the DF90 with plans to jack it way up till someone talked some sense to me When I reevaluated I decided I used the space every outing and only high speed occasionally. When I swapped motors I bought composite Trex with plans to toss my wood deck and build a composite one extending over the rudders the full width of the transom, just never got around to it.

Just remember that with an armstrong brkt it also becomes part of the hull extension @ the bottom & therefore lengthens the hull & acts as extra floatation thus nulefing excess drag , plus the the nice addition of a swim platform & additional walk-in space @ the stern

J
PS if I can find the time this spring I might just get the measurements they require & fill in there order form just to see what kinda quote I get back then see if we can get a bunch of guy,s with who would like to get one & see if we could get a better deal price wise