Manual Jack Plate

[muchco]

My intentions are to install a manual jack plate with 4" set back and 10" of vertical adjustment.<br />I understand that by raising the motor you create less drag thus your able to increase your WOT rpm and speed. My question is: What effect does raising the motor and the set back have on hole shot? I think that I have heard that the height of the motor is called the X factor. FYI. I have raised the motor on the transom with the adjustment that is available. I did not notice a great deal of difference. Does the set back help or hinder the hole shot? Any input would be greatly appreciated.

 

[Dhadley]

Re: Manual Jack Plate

Good questions. You have the theory right -- less gearcase in the water is less drag. You have to temper that with prop design, water pressure and how set up works with hull design.<br /><br />If all things are right, your holeshot should improve as well as overall efficiency. As you increase the X dimension (motor height) there will be a point at which any given prop starts slipping. Then you go to a better / different design.<br /><br />As you go up you will lose water pressure at some point. Then you have to go to a low water pick up. <br /><br />10" is a lot. About twice what we normally need/use.<br /><br />Set back changes your center of gravity forward to aft. Sometimes we refer to that as the lift point.<br /><br />Since youve run the motor on the transom and then raised it, you'll have a good baseline. Watch your water pressure. Or we'll be talking about changing pistons.

 

[muchco]

Re: Manual Jack Plate

Thanks very much for the response. What I get is that the jackplate isn't going to hurt the hole shot and will actually inprove it. I do have a water pressure gauge so I will keep and eye on that. I may have to look into hydralic steering as I'm not sure if my motor well will alow me to move the engine back 4 inches with the current steering system. I am running a 20 pitch Raker now and want to get more WOT RPM. 87 150XP Evinrude DC175 Larson. On previous post regarding Boysen reed I bored you with the details. 50 MPH gps at approx 5200 RPM. My tach indicated 5000 rpm but I'm thinking it's a little higher. I have replaced the tach and will test in the spring to confirm the RPM once and for all. Is a Raker a good prop with increased X dimension? What others would you recommend if a change is required? I'm hopping that with the jack plate and the 20 raker I should be able to pick up 200 - 400 rpm. Is this a pipe dream? Thanks again your input is greatly appreciated and respected. Muchco

 

[ob15]

Re: Manual Jack Plate

I think if Dhadley posts back, he will tell you you need more rpm's. He will help you get there too.

 

[Dhadley]

Re: Manual Jack Plate

Dave's right on. We need to verify the tach and look for 5800 with an average load. A tad more wont hurt either. <br /><br />The Raker is a good prop. A Turbo lightning Jr. is a comparable prop and very good too. I think you'll be in the ballpark with set up changes.

 

[muchco]

Re: Manual Jack Plate

Thanks for your responses. I will get the jack plate installed this month and then wait for the ice to go out to test. I will run a thread when I start testing to let you know how I make out with it. Muchco

 

[ob15]

Re: Manual Jack Plate

Perhaps the jack plate is a 10" setback with 4" lift. The 10" lift seems high. Either way sir D will get you setup real good.

 

[gatorred]

Re: Manual Jack Plate

make sure it four or more blade ss prop try adj it for take off mine will jumping coming on plane if to high you set it what the boat like's, there is some on prop forum on jackplate to on this sight scan though it www.myspace.com/boatstuff it got 175 with jack plate and prop pic to i just uploaded it,i take it off my websight now it may stay for time mine is a 150 xp very close to that my prop in canada getting fixed. I want to know what was done to it the prop it was 4 blade 13.25 x 25 pitch because I get the same thing in USA if i mess it up again mine wasn't running full power over powering prop,as fast as your's with jackplate

 

[rickdb1boat]

Re: Manual Jack Plate

Originally posted by gatorred:<br /> make sure it four or more blade ss prop try adj it for take off mine will jumping coming on plane if to high you set it what the boat like's, there is some on prop forum on jackplate to on this sight scan though it www.myspace.com/boatstuff it got 175 with jack plate and prop pic to i just uploaded it

Huummmm....??

 

[muchco]

Re: Manual Jack Plate

Sorry for the miss information, the jack plate has a 6" set back and has 4" of lift.<br />Regards Muchco