??? Jack Plate help cont. ???

[jrhubbard]

Hey guys it's me again. I have been reading some other threads and noticed that seems everyone saying that the cavitation plate should be even and no more then a inch above the bottom of the boat, is it the keel that they are calling the bottom, this is a 1990 stratos with a 1990 evindrude 150 with a six inch jack plate (manaul) I have another thread posted on here that's explains my problem with more detail long story short someone put this jackplate on and it has not been adjusted. I just trying to get the most performance out of my boat. I'm not sure what pitch the prop is that I have all I know is that is a racker brand thanks for the help

 

[JB]

Re: ??? Jack Plate help cont. ???

A setback changes the game, jr. The idea is to have the anti-ventilation plate at the surface of the water when on plane.

The water will rise higher further back from the transom, so you will want the AV plate higher. If the jackplate is powered finding the optimum height is as simple as finding the optimum trim; trial and error.

If the jackplate is manual, adjusted with a wrench, getting it at optimum height is more like finding the optimum height on a small outboard. . .adjust and try.

There are guys who say raise the outboard so many inches for so many inches of setback. I have not found those formulae useful except to establish a starting point before fine tuning.

Hope that helps. Good luck.

 

[jrhubbard]

Re: ??? Jack Plate help cont. ???

That's the problem I'm having I really don't know were I need to start, i first took the engine as high as the jack plate would allow as a starting point, I did lost five pound water pressure which put me to 25 pound but it seems as if the prop wants to wash out in right or left turns. So is it that I have my outboard to high or am I trimming it up to high

 

[ondarvr]

Re: ??? Jack Plate help cont. ???

Now that you know it's too high, you just need to drop it a 1/2 inch at a time until you go too low, then move it back up.

 

[jrhubbard]

What are the steps to make jack plate hight simply to set

What are the steps to make jack plate hight simply to set

Hey guys, on this 1990 stratos with a 1990 evinrude 150 and a six inch jack plate, this jack plate was put on the boat just before I bought it and not set, I really don't know much about jack plates or how to set them up. My question is how to do this, is their a starting point? And how high should I be trimming the motor up I really need help, I have been given some answers but I really don't understand what they mean I just don't know what I'm looking for. I first set the plate as high as it would allow but it seems as if the prop is washing out in turns, (water pressure is fine) do I have the engine set to high or is it that I'm trimming it to high. I was told depending on what prop I have that I should not have a rooster tail bigger then 24" but since I raised the engine it shoots one much higher then that. I'm not sure what pitch the prop is all I know is that it is a raker brand and it is a three blade. Please help thanks

 

[sterndrive tech]

Re: ??? Jack Plate help cont. ???

and don't worry about that water pressure gauge, 25 lbs is plenty, the bottom of the boat doesn't matter, you can start an inch or 2 above drain plug. If you don't ventilate in turns while trimmed down then you are getting close to optimum performance,, if this is a 2 piece jackplate,and there were alot around back then, throw it away and get a 1 piece

 

[JB]

Re: ??? Jack Plate help cont. ???

You get one thread per topic, jr. I have merged your two threads.

 

[jrhubbard]

Re: ??? Jack Plate help cont. ???

This boat will not ventilate in turns now with it trimmed down it's doing this at higher speeds on plain and the engine trimmed up

 

[jrhubbard]

Re: ??? Jack Plate help cont. ???

what is the wot rpm that i have seen everone talking about what does wot mean ????

 

[jchristi]

Re: ??? Jack Plate help cont. ???

wide open throttle

 

[metriccrescentwrench]

Re: ??? Jack Plate help cont. ???

I believe (but am not certain) that your Stratos is a pad-V type hull (in other words at the stern and several feet forward the bottom of the hull has a flat "pad" that is 8 or so inches wide). That would make it at least similar to my Checkmate, and I run the prop centerline 3 inches below the pad with a 6 inch jack plate using a 23 pitch Renegade prop (a 25 pitch might give me a little more speed but it's easier pulling skiers with the 23). I was told by someone with a ton of experience in high performance boat setup that unless you plan on doing a lot of running over 80 mph to just set the prop height at 2.5 to 3 inches below the pad and leave it (that's with the engine set-back on a jack plate of course), I'm happy with how my boat handles so I've got no reason to change. So I'm guessing that would also be a good starting point for your boat.

I don't buy into that "rule" that the rooster tail shouldn't be over X number of inches high. If you've ever watched drag boats there are plenty of rooster tails WAY WAY higher than what the "experts" say they should be. I'm sure those boat crews have put a ton of effort into getting every last bit of speed possible, and if big rooster tails slowed you down they wouldn't have them. A rooster tail happens when the prop pierces the surface of the water, it all depends on if a prop is designed to run like that or not.

 

[jrhubbard]

Re: ??? Jack Plate help cont. ???

is that measurement 2.5 to 3 in'' from the center of the prop to the bottom of the pad with the motor trimmed all the way down or how? And thanks seems as if what you told me kind of made it simple. When i raised my engine all the way up as high as the jack plate would allow me i gained about 2 mph but seems as if it wants to wash out in turns but i was told to trim my motor down which could be my problem because i would be running at wot with my motor trimmed up i would slow down to take a hard turn leave the motor trimmed up and it wanted to wash out. do you think that i need to lower my motor or is it that i'm driving my boat all wrong. i'm new to this whole jack plate and big engine with trim game. And my boat does have the pad as you explained

 

[metriccrescentwrench]

Re: ??? Jack Plate help cont. ???

is that measurement 2.5 to 3 in'' from the center of the prop to the bottom of the pad with the motor trimmed all the way down or how?

No, that's measured with the lower unit level with the pad. Basically you need to raise or lower the front of your trailer to get the boat's pad perfectly level fore to aft. Then trim the engine up or down 'till the AV plate is perfectly level. Now you can take the measurement, use a straightedge on the bottom of the pad (extended back to where it's above the front of the lower unit) and measure down to the point of the lower units "bullet".

As far as driving the boat, you've got to think ahead. You trim down to take off, as the boat comes on plane gradually trim up to your normal running position. Just as you're entering a turn start trimming down some (how much has to be learned through experience), and as you come out of a turn start trimming up to your normal running position again. Driving a fast boat is a lot like flying an airplane in that you've always got to be thinking ahead, and paying clolse attention to who or what is out in front of you 'cause that's where you're going to be in just a few seconds.

 

[jrhubbard]

Re: ??? Jack Plate help cont. ???

hey thanks alot you have really made this simple for me to get started to get it set right THANKS