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Repositioning The Propeller
For More Performance
Dear Jay,
I'm kind of new at this, but I set my prop back too far by mistake one time
by using prop washers. I did gain top speed, however after running 15 or 20
miles, it spun the hub. It is on a 1998 Bullet 20XD/1997 Mercury 225
Pro Max. My propeller is a Mercury Trophy propeller, equipped with the plastic hub.
if I space the propeller back using two spacers until their is only a couple of threads
left past the nut, are there enough of the propeller shaft splines on the shaft to
work with the prop, where I can safely run it with out spinning it again? The
prop shaft is 1 1/2 above pad with a Mercury Sportmaster lower unit.
Thank you,
David Higginbotham
Natchez , MS
hpost@telepak.net
David,
Moving a through the hub-type propeller, such as a Mercury Trophy,
far back on the propeller shaft will not result in as much of a gain as if
an over the hub-type propeller would, positioned in the same manner.
The through-hub type propeller directs exiting exhaust gases through the
barrel of the propeller, filling the void that would otherwise create a
vacuum if the exhaust gasses were not present. This makes these types of
propellers very efficient.
The reason why most
through the hub propellers have ventilation holes at the front of the
blades, is introduce exhaust gases onto the positive side of the blade area,
creating some controlled slip to allow the motor to spool on up into its
power band quickly. Stock OEM rubber or nylon hubs are not intended the
kinds of stresses that would result from positioning this type of propeller
farther back on the prop shaft. Also, this type of propeller is designed to
be positioned slightly “inside” the torpedo of the lower unit, forming an
efficient pathway for the exhaust gases. If your goal is to gain top speed,
an over the hub type propeller, such as a Chopper or Cleaver would be a much
better choice.
Good luck and thanks for asking JSRE,
Jay @ JSRE
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