Around 5/23/2006 2:48 PM, AlexE wrote:

Hi
I have a Tohatsu 40c (2 cyl) that now has a Tohatsu 10½ x 12 aluminum
prop. The motor turns about 6000-6100 at full throttle (max allowed
5800). If i buy a stainless steel prop (I was thinking of a Michigan
Wheel Rapture), should I get a 12 or 13 pitch? Someone told me that in a
case like this, if the revs are slightly high, get a stainless prop with
the same pitch as the alu prop, that'll take some rpm off, presumably
because the alu prop flexes ever so slightly and the steel does not. The
boat is 14 ft and weighs about 350+ kg including me. Comments? Suggestions?
Rgds
Alex

My setup is almost identical, except a bit heavier (~430 kg with me,
gas, and normal gear):

I've got a Nissan 40d (3 cyl) that came with the same 12" pitch prop on
a 14' fiberglass runabout, and I couldn't even go full throttle without
hitting the rev limiter. I went with the highest pitch replacement
aluminum prop Michigan Wheel makes (10.2" X 13.9"), and I have been
extremely happy with it. Revs are perfect, 5400 at full throttle (manual
says the max should be 4500-5500), and the top end picked up almost 7
knots. It'll still pull up a big skier and even uses less fuel to cruise
at the same speed as with the old prop.

Now, you don't need to lower your RPMs as much as I did (the two
cylinder is a little more rev happy, so the 13" would probably suit your
boat well. You might even be able to squeeze a little more speed out of
the 14" and still be inside your ideal RPM range.

I've got very little opinion one way or the other with stainless vs.
aluminum. I don't tend to hit things, so I opted for the cheap aluminum
over the durable SS.


--
~/Garth - 1966 Glastron V-142 Skiflite: "Blue-Boat"
"There is nothing - absolutely nothing - half so much worth doing
as simply messing about in boats." -- Kenneth Grahame
~~ Ventis secundis, tene cursum ~~

"Garth Almgren" wrote in message
...
Around 5/23/2006 2:48 PM, AlexE wrote:

Hi
I have a Tohatsu 40c (2 cyl) that now has a Tohatsu 10½ x 12 aluminum
prop. The motor turns about 6000-6100 at full throttle (max allowed
5800). If i buy a stainless steel prop (I was thinking of a Michigan
Wheel Rapture), should I get a 12 or 13 pitch? Someone told me that in a
case like this, if the revs are slightly high, get a stainless prop with
the same pitch as the alu prop, that'll take some rpm off, presumably
because the alu prop flexes ever so slightly and the steel does not. The
boat is 14 ft and weighs about 350+ kg including me. Comments?
Suggestions?
Rgds
Alex

My setup is almost identical, except a bit heavier (~430 kg with me,
gas, and normal gear):

I've got a Nissan 40d (3 cyl) that came with the same 12" pitch prop on
a 14' fiberglass runabout, and I couldn't even go full throttle without
hitting the rev limiter. I went with the highest pitch replacement
aluminum prop Michigan Wheel makes (10.2" X 13.9"), and I have been
extremely happy with it. Revs are perfect, 5400 at full throttle (manual
says the max should be 4500-5500), and the top end picked up almost 7
knots. It'll still pull up a big skier and even uses less fuel to cruise
at the same speed as with the old prop.

Now, you don't need to lower your RPMs as much as I did (the two
cylinder is a little more rev happy, so the 13" would probably suit your
boat well. You might even be able to squeeze a little more speed out of
the 14" and still be inside your ideal RPM range.

I've got very little opinion one way or the other with stainless vs.
aluminum. I don't tend to hit things, so I opted for the cheap aluminum
over the durable SS.

And if you do hit things ..... how about trashing out a cheap aluminum prop
and not a shaft?