do i need a new porp to use with jake plate

[josh_2562]

I put a jakeplate on my boat but when i try to lift the engine up it just start to slow down and rev high. i was told by a friend that i might need to change my prop to a higher pitch.thanks for any help josh

 

[studlymandingo]

Re: Do I need a new prop to use with jack plate?

Re: Do I need a new prop to use with jack plate?

Josh you will need to be a bit more specific to get an accurate answer.​

What type of boat do you have?
What is the horse power of your motor?
What is your WOT RPMs?
What is your speed at WOT?
What prop are you currently running?
How much setback does the jack plate provide?​

 

[WillyBWright]

Re: Do I need a new prop to use with jack plate?

Re: Do I need a new prop to use with jack plate?

I'm not sure a higher pitch would be the solution, but a different prop of about the same pitch might be. As you jack the motor up, the prop is more likely to suck air. Some props maintain hold better than others. If you currently have an aluminum prop, you definately need to get a stainless to take advantage of higher heights. Aluminums have to run fully submerged. Three-blade stainless props can come out a bit higher, 4-blade starinless quite a bit higher, and High-Five props even higher yet. You also have to be careful to keep the water intakes for the water pump submerged or you'll suck air and overheat the powerhead.

 

[josh_2562]

Re: do i need a new porp to use with jake plate

What type of boat do you have?
What is the horse power of your motor? 1992 merc 100
What is your WOT RPMs? 5100
What is your speed at WOT? 43
What prop are you currently running? 13 1/4x17ss
How much setback does the jack plate provide?5"

took the boat out today got it up to 43mph by boat speedo(i don't have a gps)it took alot of adjusting to get it to 43mph.this was a wot if i let off at all it would porpois really bad. i left the jackplate where it was on this runn and put it on the trailer.so if you need me to measure any thing i can. thanks for any help josh

 

[Esox]

Re: do i need a new porp to use with jake plate

If your going to be playing with engine height it's strongly recommended to install a water pressure gauge if you don't already have one.​

 

[Esox]

Re: do i need a new porp to use with jake plate

Take a measurement of the A/V plate in relation to the bottom of the hull.​

 

[josh_2562]

Re: do i need a new porp to use with jake plate

can do. if i remember right i leval the boat and the engine then take the measurement right or wrong. thanks for the help

 

[josh_2562]

Re: do i need a new porp to use with jake plate

Take a measurement of the A/V plate in relation to the bottom of the hull.​

it's 2" above the hull if i'm measureing the right thing. the bullet is 5 1/2 below the hull. shouldn't i be able to lift it higher then this. i still have about 2" higher let on the jack plate. thanks for the help

 

[Esox]

Re: do i need a new porp to use with jake plate

Depending on the style of prop and hull type you should be able to go higher. A general rule of thumb is for every 5" you move the engine back you should be able to raise the engine 1" higher. On my deep v aluminum with a 5" setback I'm running mine 3" above. I still have more playing to do with mine so I'm not sure where it will end up when I'm done.​

 

[studlymandingo]

Re: Do I need a new prop to use with jack plate?

Re: Do I need a new prop to use with jack plate?

Your WOT RPM seems a bit low. It should be more in the mid to upper 5Ks You need to get this figured out as you could have some serious issues with coking and seizure. According to the current RPM readings, you would need to drop pitch by 4 which just doesn't seem right.

Is the motor running properly?

What you need to measure is the A/V plate (this is the plate just above the prop), and yes it should be a couple of inches above the bottom of the boat.

Do you have a water pressure gauge? You can raise the motor as long as you don't sacrifice cooling water pressure.

As to the porpoising, do you have any type of trim tabs?​

 

[josh_2562]

Re: Do I need a new prop to use with jack plate?

Re: Do I need a new prop to use with jack plate?

i thought it seemed low also. the engine seems to be runing good. the a/v plate is 2" above the hull.I don't have a water pressure gauge yet. where is a good place to get one.I don't have any trim tab

Your WOT RPM seems a bit low. It should be more in the mid to upper 5Ks You need to get this figured out as you could have some serious issues with coking and seizure. According to the current RPM readings, you would need to drop pitch by 4 which just doesn't seem right.

Is the motor running properly?

What you need to measure is the A/V plate (this is the plate just above the prop), and yes it should be a couple of inches above the bottom of the boat.

Do you have a water pressure gauge? You can raise the motor as long as you don't sacrifice cooling water pressure.

As to the porpoising, do you have any type of trim tabs?​

 

[studlymandingo]

Re: do i need a new porp to use with jake plate

I would try going up a little bit more first.​