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NEVER operate the propulsion engine while
everyone on-board is sleeping. Fatal carbon
monoxide poisoning can occur.
For.additional.information,.refer.to.Section.B-2.Carbon.
Monoxide.
E - 3
ENGINES
Consult.the.Engine.Owners.Manual.included.in.the.
owner's.packet.for.additional.operation.and.mainte-
nance.information.
E - 4
PROPELLERS
Knowledge.of.the.propeller.is.most.easily.gained.
through.better.understanding.of.the.terminology.used.
to.refer.to.the.aspects.of.propeller.size.and..
performance.
NOTICE
Never run with a damaged propeller. You can
damage the engine or drive unit. Keep a spare
propeller on board.
A. Diameter
Diameter.is.twice.the.distance.from.the.center.of..
the.prop.shaft.to.the.extreme.tip.of.a.propeller.blade..
Increasing.or.decreasing.propeller.size.will.have.a.
direct.bearing.on.the.RPMs.(revolutions.per.minute).an.
engine.will.develop..This.is.due.to.the.greater.amount.
of.propeller.blade.surface.in.contact.with.the.water..
See.Figure.E1.
B. Pitch
Pitch.is.a.measure.of.helix.angle,.or.angle.of.attack,.
of.the.rotating.blade..Pitch.is.easily.understood.if.one.
imagines.the.propeller.rotating.through.a.semisolid.
such.as.butter.or.jello..The.distance.the.propeller.will.
travel.in.one.revolution.is.called."Pitch."..Increasing.
or.decreasing.pitch.will.also.have.a.direct.bearing.on.
engine.RPMs.because.of.the.greater.bite.taken.by..
the.blade.with.each.rotation..See.Figure.E-1.
Engines and Instrumentation - Section E
Figure E-1: Propeller Pitch & Diameter
C. Prop Slip
When.traveling.through.water,.a.propeller.is.unable.
to get a complete bite because of the fluidity of water.
"Prop.slip".is.usually.expressed.as.a.percent.of.the.
computed theoretical speed. Fifteen to twenty-five
percent.prop.slip.is.common.for.a.sport-type.boat.
operating.at.cruising.speed.
Changing.either.diameter.(Rx2).or.pitch.will.have.
an.effect.on.engine.speed.and.prop.slip,.and.in.
turn,.directly.affect.the.performance.of.a.boat..The.
propeller(s).included.with.each.Four.Winns
provide.the.best.general.performance.based.on.data.
obtained.from.on-the-water.testing.of.that.model..
Variations.in.load,.operating.conditions,.environ-
ment,.the.individual.engine.and.hull.performance.
may.necessitate.the.purchase.and.use.of.another.
propeller(s).
.
Under.your.normal.load.conditions.the.engine(s).
should.turn.within.the.maximum.RPM.range.when.
at.full.throttle..If.the.engine(s).exceeds.the.recom-
mended.RPM,.an.increase.in.pitch.and/or.diameter..
is.required..If.the.engine.RPM.is.too.low,.a.decrease.
in.pitch.and/or.diameter.is.required.
Radius
.boat.
®
Owner's Manual Page
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