Question on Jackplate Adjustment.

[chan93lx50]

I installed a 6 inch Jack plate on my 1987 Ranger Fish and Ski, I am currently running with a 23p High Five prop, and a 175 Merc. At WOT my RPM is 6000 @ 50 MPH.

I am wondering if I can go up further on my jackplate or do I need to drop it back down.

When running WOT, I cannot tilt my motor all the way up without losing H2O Pressure. My question is should I be able to tilt the motor to to the max and hold H2O pressure when I have the Jackplate setup correctly? It run good and turns with out losing H2O pressure but if I tilt the motor up beyond a certain point I lose pressure.

I am used to having the motor mounted on the back of the transom and when I go WOT I could hold the tilt/Trim button until the motor stopped trimming up and not lose any H2O pressure. Should this be the same for when I have the jackplate installed?

Am I making sense?

 

[hwsiii]

Re: Question on Jackplate Adjustment.

chan, you have the motor moved up much higher in the water column than it was when it was mounted on the transom, and that is a normal reaction to the difference in heights.

My question is should I be able to tilt the motor to to the max and hold H2O pressure when I have the Jackplate setup correctly? It run good and turns with out losing H2O pressure but if I tilt the motor up beyond a certain point I lose pressure.

Everything is fine it appears, if you will give me your gear ratio and max recommended WOT RPM, we will see exactly how well it is running.



H

 

[chan93lx50]

Re: Question on Jackplate Adjustment.

Gear Ratio is 2:1, WOT with the 23P High Five prop I was 6000 48 to 50mph.

WOT with a Turbo II 25p prop I was 5800 57MPH

So can I continue to move the motor up? I obviously just need to make sure when I am running on plane I do not trim the motor past the point where I loose H2O Pressure.

Or am I already past the point of increasing the Jackplate since I lose H2O pressure when Triming the motor?

 

[mikel7]

Re: Question on Jackplate Adjustment.

I have always heard that the fish tail should not be higher than your motor. Take note the boat advertisements on tv. Going to high will cause a lose in speed. If you are losing psi you are way to high.

 

[hwsiii]

Re: Question on Jackplate Adjustment.

chan, after running the numbers I can see that you evidently do have the motor mounted too high on the boat, because your prop slip appears to be higher than it should be for that type of hull, especially the high five, and that makes no sense to me.

Prop Slip

So lower it 1" and lets see what happens.

H

 

[chan93lx50]

Re: Question on Jackplate Adjustment.

Will do, I will be taking the boat out this coming weekend will post my results,

Thanks
Channon