Manual jack plate starting height

[BWR1953]

I just started setting up a manual jack plate that came with a donor boat & 150HP Mercury XR6 engine that I bought. The donor was a bass boat and my boat is an aluminum V-hull fish 'n' ski with no pad. The jack plate has a 4" set back.

I've not splashed the boat since the repower and I'm a bit concerned about the jack plate starting height. We have the JP as low as it will go and the AV plate is a good 2 inches above the bottom of the hull.

I know that for a normal setup without a JP, that keeping the AV plate even with the bottom of the hull is a good starting point. I've done that with a lot of my boats.

And, I know that with a JP, the AV plate can safely run quite a bit higher; in some cases as much as 4 or 5 inches above the AV plate.

All that being said, I'm nervous about beginning with the AV plate 2" above the hull bottom. I don't have water pressure or temperature gauges, but they're in my future plans.

I have pix, but can't post them due to the current site issue.

Thoughts, please.

 

[Chris1956]

That starting point is probably fine. Check to make sure she is pumping water when on plane, but I expect she will be fine. A trick is to close up the top water intake hole and enlarge the bottom one.

Just so you are expecting it, as you raise the engine height, the trim loses influence. At max engine height, the trim may have no influence on the bow of the boat. Depending on how much you need to trim the boat to get max speed, will dictate the setting of the JP height.

 

[Scott Danforth]

rule of thumb with setback. for every 4" back, raise the motor up 1"

so with the 4" of setback on the transom jack, I would have the AV plate 1" higher than normal as a starting point. you will blow out prior to running out of water.

 

[BWR1953]

Thanks for the answers guys.

After reading more, especially over at screamandfly, I've decided that I'm going to remove the jack plate and mount the engine directly to the transom. I just don't want to hassle with a lot of adjustments, especially with a manual jack plate. Some of the guys made hundreds and even thousands of adjustments in increments as small as 1/16". Nope.

I guess I need to buy some more 5200 and rubber gloves.

Thanks again for the help.

 

[Scott Danforth]

Can you convert to a hydraulic jack plate? That's the ticket

 

[BWR1953]

Can you convert to a hydraulic jack plate? That's the ticket

Not in the budget. As usual.

 

[redneck joe]

learn me why one would want to jack with a jackplate.

 

[Scott Danforth]

learn me why one would want to jack with a jackplate.

because simply tilting doesnt always cut it as the tilt also changes the bow attitude but doesnt raise the motor. many flats boats use jack plates in addition to T-n-T to run perfectly flat in 4" of water by getting the boat on plane, trimming it out, then raising the motor to get that perfect prop bite while enabling the boat to get to places most v-hulls can not normally go

a manual jack plate only makes sense if you are dialing in a racing boat, as recreational boats have too much weight changes.

a manual jack plate also allows the motor to sit a bit higher while being moved aft. this is good on some types of transoms where a short or long shaft may be just a tad short and the next length up is too long.

a powered jack plate is what should be on boats like pontoons where any shift in weight greatly affects the prop bite.

 

[redneck joe]

Ok, I'll stay jack free...

 

[BWR1953]

Ok, I'll stay jack free...

Yes, my jack plate was free.

 

[Chris1956]

I had a JP on my speedboat for some years. The real issue I had was that it made the boat tricky to drive, as the motor needed to be fully down to get on plane. then it had to be trimmed just right. When you did this, you did achieve some extra speed, however, I was the only one who knew how to drive it, and it was a PIA. The extra speed was achieved at 60+MPH, which is a speed I hardly used.

I eventually just lifted the motor up a notch or 2 and bolted it to the transom. It is much more drivable, and the transom is a bit lighter, without the JP setback.

 

[BWR1953]

I had a JP on my speedboat for some years. The real issue I had was that it made the boat tricky to drive, as the motor needed to be fully down to get on plane. then it had to be trimmed just right. When you did this, you did achieve some extra speed, however, I was the only one who knew how to drive it, and it was a PIA. The extra speed was achieved at 60+MPH, which is a speed I hardly used.

I eventually just lifted the motor up a notch or 2 and bolted it to the transom. It is much more drivable, and the transom is a bit lighter, without the JP setback.

I read about that tricky driving part, which also influenced my decision to delete the plate. Some guys said that it could get really squirrelly at speed; something I definitely don't want to worry about.

 

[Chris1956]

Squirrelly at speed is not a function of the Jack Plate itself. It is a characteristic of the hull, that can occur at high speed. Now if the Jack Plate increases your speed enough to achieve that squirrelly feel...

I just found the JP to be more of a PIA than I liked, as trim needed to be exact

 

[redneck joe]

i had a boat with a blax max 150 that would do 73 with me and a six pack. i drink more than a six pack so i sold it. way to fast for me.

 

[BWR1953]

...a manual jack plate only makes sense if you are dialing in a racing boat, as recreational boats have too much weight changes.

a powered jack plate is what should be on boats like pontoons where any shift in weight greatly affects the prop bite.

The boat my manual JP came from was a bass boat. (I'd post a pic, but you know. ) The owner said that it was typically only himself on board, rarely two. And both sitting side by side at the console. The owner also told me that he routinely pushed 70MPH with the boat and loved how it performed. If I had the budget, I wouldn't buy a hydro/electric jack plate, I'd buy a brand new bass boat!

Squirrelly at speed is not a function of the Jack Plate itself. It is a characteristic of the hull, that can occur at high speed. Now if the Jack Plate increases your speed enough to achieve that squirrelly feel...

I just found the JP to be more of a PIA than I liked, as trim needed to be exact

Yeah, from what I've learned, it definitely looks like a PITA. Over the next few days, I hope to get an opportunity to get out to the garage in the morning and determine if I can remove the jack and put the engine on the transom without making changes to the steering and shift/throttle cables. Been very busy this week.

i had a boat with a blax max 150 that would do 73 with me and a six pack. i drink more than a six pack so i sold it. way to fast for me.

I used to have a lightweight glass fish 'n' ski bass boat with a Mariner 150 and that thing flew. I got 72MPH with just me on board and 68MPH with my big cousin along. Loved it! Never had any chine walking or other bad behavior. Really nice boat. My favorite of all my boats.

 

[cyclops222]

Erratic control at maximum speeds ???? Dangerous as can be. My Chaparral with the factory Planning Pad on the bottom was DANGEROUS !! At 52 GPS it felt like I was riding a bowling ball. Any turning a little bit caused SCARY boat yanking and leaning. DO NOT get too fast for the boat to run out of control !! You can be safe. BUT What happens if someone else is a speed nut driving it ?

 

[Chris1956]

Cyclops, Most novice drivers do not know to trim it up until they lose control. Kinda like how God protects drunks from themselves.

On my speedboat, if she is only trimmed until the steering is light, she is safe. The steering needs to pull left, before she gets dangerous. Takeoff speed is about 50MPH. She will cruise easily at 55MPH. Heck wifey was sunbathing topless at 55MPH on a calm day.

I let my 20+ YO niece drive it one time. I said to her, "you realize that you are out of control at this speed, right?". She didn't see it but slowed down a bit.

 

[cyclops222]

Problem is ........Every new to boating person thinks and drives it like a car. Can be fatal the first time.

 

[redneck joe]

The boat my manual JP came from was a bass boat. (I'd post a pic, but you know. ) The owner said that it was typically only himself on board, rarely two. And both sitting side by side at the console. The owner also told me that he routinely pushed 70MPH with the boat and loved how it performed. If I had the budget, I wouldn't buy a hydro/electric jack plate, I'd buy a brand new bass boat!


Yeah, from what I've learned, it definitely looks like a PITA. Over the next few days, I hope to get an opportunity to get out to the garage in the morning and determine if I can remove the jack and put the engine on the transom without making changes to the steering and shift/throttle cables. Been very busy this week.



I used to have a lightweight glass fish 'n' ski bass boat with a Mariner 150 and that thing flew. I got 72MPH with just me on board and 68MPH with my big cousin along. Loved it! Never had any chine walking or other bad behavior. Really nice boat. My favorite of all my boats.

Mine was a 16 Stratos, but not bass. Closed bow, bucket seats only. Black and silver we called it the batman boat. Had it reupholstered and had him put in batman signs on the seats.

I'll stick with my 28 mph WOT now.

 

[KJM]

because simply tilting doesnt always cut it as the tilt also changes the bow attitude but doesnt raise the motor. many flats boats use jack plates in addition to T-n-T to run perfectly flat in 4" of water by getting the boat on plane, trimming it out, then raising the motor to get that perfect prop bite while enabling the boat to get to places most v-hulls can not normally go

a manual jack plate only makes sense if you are dialing in a racing boat, as recreational boats have too much weight changes.

a manual jack plate also allows the motor to sit a bit higher while being moved aft. this is good on some types of transoms where a short or long shaft may be just a tad short and the next length up is too long.

a powered jack plate is what should be on boats like pontoons where any shift in weight greatly affects the prop bite.

Not sure I'd want to be at planning speed in 4" water in any type boat! Thats where I get out and walk....