Jackplate Set up

[badss350]

Just recently got a Pro-Hi jacker 6" for my 18' 91 Charger...What is the proper way to get max use out of it as far as setting it up...I was told to keep raising it 1" at a time til my RPM went up and speed drops then back it down 1/2 inch...Do I do this will full trim? Im running a 24 pitch Raker on a GT 150...I want max top end speed...I have it almost half way up now, and rpm is only 5200 and speed about 60 on new speedo...Im changing plugs today and running it today...I think the old plugs may have a lil to do with rpms...So do I set this up using full trim?

 

[NSBCraig]

Re: Jackplate Set up

No start with your trim level and your anti vent plate 1" above the keel.

The set back helps to fly the nose already so you don't need as much trim angle.

 

[badss350]

Re: Jackplate Set up

OK, just went outside and took some measurments as explained in this article
http://www.bogerprops.com/Jackplate.html

I set trailer level and trimmed down til motor was sitting level (using a level on both) ...then from bottom of my pad to ground was 15" and from center of prop to ground was almost 11"...Im almost half way up on the plate...According to this I need to raise another inch? Im still running good water psi last time out at wot...Do i need to go up more than one inch to make it 3 below my pad?

 

[badss350]

Re: Jackplate Set up

Just swapped out the prop....mine was a 22 raker "worked to 24" I put on a new true 24 Raker from my cousins boat...raised the jack plate up a lil over and inch...also found that throttle may not have been opening all the way..the cam on roller was not sliding the bar on the throttle all the way, but gonna pull breather and make sure butterflies are flat at WOT...I really think my plate needed to be raised..at full trim and wot, rooster would not go over cowl...on cousins boat it would go 25+ft in the air (yea i know thats not max performance) I think mine should do that as well if I wanted...same boat etc...Anyways, about to head to lake and try it out..BTW...he has his plate all the way up on his..Im about an inch or so from being all the way up now...will see how she works

 

[badss350]

Re: Jackplate Set up

Well after testin on lake...best i could get was 62 on speedo at only 5200 rpm...raised up and got more rpm, but speed and water pressure dropped. Had new plugs etc...i wonder why im only getting 5200 rpm? Maybe this 24 Raker prop is too much? I have heard I could actually gain more speed with a lower pitch prop? I have seen test in BWB mag, and the speed diff from 5200 to 6000 was a big gain...any ideas?

 

[mrdancer]

Re: Jackplate Set up

How far up you can go with the jackplate depends partly on the amount of setback that is built into it - generally more setback = higher lift. I would start with the antiventilation plate on the lower unit mounted about one inch above the pad - this is with the jackplate run about one-third to halfway up, motor trimmed out level. When testing, run the jackplate all the way up and keep an eye on water pressure, should have at least 15psi at WOT.

The correct prop is the one that will just barely let you touch the upper end of your engine's max rpm range with the jackplate jacked all the way up. If you can't do that with the 24 Raker, then you have the wrong prop.

Mercury has a program where certified dealers will work with you and let you try different props before you buy. Most good outboard/prop shops will do this also, as long as you don't put a nick in the prop during your testing. Anywayz, a lot of the Merc props will fit a lot of different brands of motors because many of them have Flo-Torq hubs that can interchange among mfrs. That would be the route that I would take. Merc makes some good props. Look around this website http://tinyurl.com/6cpche
for good info on prop basics as well as Merc's various props.

For performance beyond that, you would need to go to custom prop shops, like Baumann's in Houston, TX.