1 Hour 5.2 mph increase - worked

[boknows]

I read that on a tunnel hull the centerline of the prop should run 3" above the back of the bottom of the center pontoon on my hull. I was running 3 inches below with the jack plate all the way up. We remounted the motor on the highest setting and got 2 inches above the bottom of the center pontoon and it increased 5.2 mph. i had never heard of this. I realize that every boat hull is different and that there are many variables but I am new and I thought this thread and any helpful post would be good for people like me who don't know anything. I love this site...


Exact steps we did...
1: Leveled the boat and motor
2: Measured the center of the prop to the ground
3: Measured the center of the cone to ground and measured from middle pontoon to ground to see where we stood.
4: We adjusted the way the motor mounted to the jack plate and then we remeasured.

Good luck.

PS.. We do have a low water pickup and this may not work for your boat. If you kill yourself don't come to me. Im scared of ghost....

[stvhelm]

I dont think 3" up above the pad would pick up any cooling water. be happy at 2" congrats on the 5mph:)

[Fish]

congrats boknows, that is a big gain. Most people do not realize how much gain there is in proper setup and prop selection. Keep an eye on that water pressure.

fish

[Ripper]

Just another example of the great family here...

Ripper

[Riverratt]

I would think 2" above would be too high but if it is working for you great. 3" below was definatley too low for your boat. You might want to try going up or down a little at a time and see how it affects speed and water pressure. Like someone else said setup is where it is at and it could be different for every prop you try.

[hsbob]

hopefully your not running that shifting prop???

[Riverratt]

hopefully your not running that shifting prop???
I was thinking the same thing but when I saw the lower unit did not have a low water pick up I assumed the pics were for reference only. If that is the prop he is using it will be missing a few blades real quick at that height. The old land and sea blade slinger.:p

[joneill]

any ideas on height for a 24 superboat i/o?

[vnemous]

With an I/O your kinda stuck with the x dimension it came with. Unless you have the upper shortened and thats not easy, but can be done.

[joneill]

i am 6" below the v
was wondering about ext. boxs?
also about a shorty drive?

[hsbob]

yes please sell that prop while its in good condition.

[GPRACING]

If you're surfacing that shifting prop you wont be doing it for long!Time for a new prop.I hope you're running a low water pickup.Congrats on the gain!