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Bill,
What you have will probably work fine. A
trolling motor's design isn't that much different from a sub thruster.
They both go relatively slow in the water. Where you really see the difference
in props is in a power boat prop. Something that cruses on the
water.
Just go on with what you have. I'm sure Minnkota
has the prop and motor matched quite well. You may find that the trolling
motor may run at a little higher amperage pushing a more resistant sub then it
would on a surface craft. But, this is off set by the fact that your
probably going to use the thruster far less then it was designed for and seldom
at full thrust giving it time to dissipate any extra generated heat.
What I would do is, when your doing you first wet
test of your sub, have an amp meter to monitor the current draw of the
thruster. If your over the rated amperage you can either reduce some of
your props diameter, or take some off the trailing edges to remove it's surface
area or flatten it out to reduce it's bite in the water. Be careful if you
trying to change the pitch so you don't crack it. Also be careful when
remove material so the prop stays balanced.
My uneducated guess is, Minnkota did the work for
you. You'll probably be fine with it as it is.
Dan H.
----- Original Message -----
Sent: Thursday, February 17, 2005 2:16
AM
Subject: Re: [PSUBS-MAILIST] Dan, you got
me wondering about my prop.
Hi Dan.
You wrote below......
"The surface craft needs a faster prop speed just to travel through the
water and additional
speed to produce thrust. The slower moving sub needs
less prop speed to
screw through the water and additional speed to produce
thrust.
By now I'm sure most of you are thinking, but the surface boat uses
a
different pitch prop. True! A faster moving boat uses a prop
that has a
long lead, more pitch. For one turn of the prop it is
designed to screw
farther through the water then a slower moving boats
prop. This is taken
into consideration with propelling a sub.
Any slow moving craft has a
flatter prop then a fast moving craft. If
the pitch of the prop were all
the same the fast boat wound need a zillion
RPM and a subs props would be
turning extremely slow."
You got me to thinking. I have a two man wetsub
and a 74lb thrust minnkota motor with the 11 inch Minnkota weedless wedge
prop.
Is that prop going to be ok for use on my sub
since it is designed for being a surface craft trolling motor? Do I need a
prop
with a different pitch?
When you were explaining about how a surface
craft needs a different prop from a sub it got me to thinking if I might
need
to get another prop for my sub.
Kindest Regards,
Bill
Akins.
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