Need help with jack plate set-up!

Just bought a '93 Nitro 170 with a 115 Merc. Came with jack plate and
with small porpoise fins or whatever they are called. The boat pulls
very hard right coming out of the hole; trimmed under. Flat out
running about 50 at 5200rpm it pulls slightly left. I know I can
adjust the trim tab but feel it would have a bigger impact at full
speed. Would be scared to get too much pull at top speed as it feels
like it is skimming a little bit as is. Should I lose the porpoise
fins? Does it sound like the jack plate needs adjusting up? or down?

I can't help answer any of these questions, but until Pat Goff shows up,
check the guys at Nitro Owners website:
http://www.nitroowners.com/nitroowners/

I think Huck pointed me there when I bought my Nitro 700LX, and they've been
a great source for information.

Oh Yeah, Pat Goff is da man, so listen closely to him.


"thesportwagon" wrote in message
oups.com...
Just bought a '93 Nitro 170 with a 115 Merc. Came with jack plate and
with small porpoise fins or whatever they are called. The boat pulls
very hard right coming out of the hole; trimmed under. Flat out
running about 50 at 5200rpm it pulls slightly left. I know I can
adjust the trim tab but feel it would have a bigger impact at full
speed. Would be scared to get too much pull at top speed as it feels
like it is skimming a little bit as is. Should I lose the porpoise
fins? Does it sound like the jack plate needs adjusting up? or down?

More of a tilt/trim issue?

sket

thesportwagon wrote:
Just bought a '93 Nitro 170 with a 115 Merc. Came with jack plate and
with small porpoise fins or whatever they are called. The boat pulls
very hard right coming out of the hole; trimmed under. Flat out
running about 50 at 5200rpm it pulls slightly left. I know I can
adjust the trim tab but feel it would have a bigger impact at full
speed. Would be scared to get too much pull at top speed as it feels
like it is skimming a little bit as is. Should I lose the porpoise
fins? Does it sound like the jack plate needs adjusting up? or down?



For the benefit of those that can answer your question and just so they
will know. What prop do you currently have? The size and pitch?

From the hard pulling I would guess you have a big 3 blade of some
kind. But knowing should help Pat or someone else answer your question.

Torque pull is normal on most performance boats. You're feeling torque pull
one direction when the prop is buried in the water at take off, then a
different direction when the prop surfaces.

It should be pulling to the right, which means you're holding a left turn to
correct it. That is normal. It can be relieved some with some minor
modifications.

First, you can adjust the torque tab on your motor, 9/16" deep socket,
loosen the bolt holding the torque tab and move it all the way to the right
(driver side) that should help most of it. If it's still more than you
like, you can purchase an aftermarket torque tab that attaches to your skeg,
and that will take 90% of wheel torque away.

But, one persons perception of "a lot" is anothers "normal"

"Carlos" wrote in message
...
thesportwagon wrote:
Just bought a '93 Nitro 170 with a 115 Merc. Came with jack plate and
with small porpoise fins or whatever they are called. The boat pulls
very hard right coming out of the hole; trimmed under. Flat out
running about 50 at 5200rpm it pulls slightly left. I know I can
adjust the trim tab but feel it would have a bigger impact at full
speed. Would be scared to get too much pull at top speed as it feels
like it is skimming a little bit as is. Should I lose the porpoise
fins? Does it sound like the jack plate needs adjusting up? or down?



For the benefit of those that can answer your question and just so they
will know. What prop do you currently have? The size and pitch?

From the hard pulling I would guess you have a big 3 blade of some
kind. But knowing should help Pat or someone else answer your question.