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Jackplate for a 150 XR6

"Need to back up for a minute.

"Need to back up for a minute.

What are you trying to accomplish?

Just fine tune the mount?

Trying to recover some deckspace?

Have a 20" shaft and 25" transom (or vice versa)?

I guess the real question is "why do you think you need (or) why do you want a jackplate in the first place"?

The answer to that question will determine "what is the best option for you"...

I personally run one - have my 140 Ev hooked to it - done to try and perfectly trim the motor to get the best possible gas mileage and, since it's mounted on a custom built boat, I opted for a 6" set back to allow the motor well to be constructed slightly smaller than would have otherwise been required, saving 4 sq ft of deck space..."
 
"I am wanting to fine tune mot

"I am wanting to fine tune motor for speed and gass mileage, and I would also like to free up some deck space. The reason I need to know what size is on my uncle's 1995 Javelin with a 200H.P. Yamaha he was told nothing smaller than a 10 in. or it wouldn't drive right."
 
"That's non-sense.

Jack


"That's non-sense.

Jackplates have (non-standard) amounts of set back dependant on the mfg.

You will see 4", 5.5", 6", 10" and 12" as "common" with generally 5-6" of vertical travel.

Assuming the motor was correctly fitted in the first place, such that the shaft length matches the transom, making slight trim changes can give you better "gas mileage" and possibly an extra 1 or 2 mph at top end.

There is no real formula to figure how much back or how far up. It often comes down to simply "fiddling" with the vertical adjustment and then checking the result using a fuel flow meter.

A sorta starting point is, for every 4 inches of setback you can raise the motor about an inch and a half - but that really is a pretty loose rule because literally every hull (even if the same model) will be a little different.

Now perhaps other Javelin owners have found that a 10 inch setback is optimal on that particular hull but I would like to see their numbers because I believe you would be talking about infantismal differences in performance if you compared a 6" and 10" plate....

However, if it's just pure speed you are after, then I do agree that the further back and the further up the better.

Mounting a motor, particularly on a bass boat hull, as far back as possible with so much vertical lift that the prop breaks the surface occassionally will give you MORE SPEED, but it's really hard on the motor and it guzzles gas.

But hey, if you have to beat everyone else on the lake to that weed patch on the other side (read pros with deep pocket sponsors who will pay for a new motor when they toast it as long as they win the tournament), it can be accomplished with a jack plate.

Purely for fine tuning you need nothing more than 4" setback and 5" vertical adjustment.

One final note. Since this is going on a hull that is 15 years old, I really would have the transom inspected. If there is even a hint of delamination it could spell disaster (and a motor at the bottom of the lake to boot).

A plate puts a significant amount of stress on a transom. Think of a teeter totter. If someone sits close to the middle it's easier to raise them than if they sit back at the seat - so conversely, the further out they are the more leverage they have - and that force increases exponentially.

So while a 4" setback may exert "x" amount of stress, an 8" setback doesn't exert 2x it's more like 8x the amount. If the transom is weak due to existing un-noticed damage, it will quickly part company from the rest of the boat (or alternately, the plate, with the motor connected, will pull the bolts through the transom and head for the bottom of the lake)..."
 
"I will just leave you with an

"I will just leave you with another thing or two to consider.

When you hear (from me or anyone else) that a "jack" will improve gas mileage and top end speed you should realize that we are talking about fairly small numbers.

By fiddling with my plate I was able to go from 6.2 gallons per hour at cruise to 6.0

That really isn't alot depending on how much you boat.

For example, most guys don't have the gear in their driveway to remove and reinstall a 300 or 400 pound outboard, so they go to a shop.

Even a simple plate will run you a couple hundred bucks plus probably another 300 to install. So for the sake of arguement, say you are all in at 600 bucks (on the very low end of things).

If you improve your gph by .2 you will save 2 gallons of gas for every 10 hours of run time. North of the border where we pay higher prices that equates to about 7 bucks.

I typically run 300 to 400 hours a year so for me a plate saves me about 210-280 bucks. (plate in my example would pay for itself in 2 1/2 years, and then I would start saving money in year 3).

But I am not the "average" boater. Look at any 10 outboards that are 5 years old and probably 6 of them barely have 100 hours on them, another 2 or 3 may have between 100-200.

So for the average boater they may never recover the cost of the install.

If gas is $3/gallon it could take over 1300 hours of run time before you break even on a low end install.

As to speed, at wide open throttle under perfect conditions, you may see an increase of up to 2 mph. Nothing that you will really notice.

The truth of the matter is, if the boat and motor are running a properly matched prop there is almost nothing you can "add on" that will make a significant or noticable difference to the performance.

And if the boat will be run less than about 200 hours a year, then there won't even be any real cost saving by spending the money to install a Jack....."
 
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