<TABLE border=0 cellSpacing=0 cellPadding=0 width=500><TBODY><TR><TD></TD><TD height=20></TD><TD></TD><TD></TD></TR><TR><TD></TD><TD vAlign=top colSpan=3 align=left><TABLE border=0 cellSpacing=0 cellPadding=0><TBODY><TR><TD height=3 width=3></TD><TD bgColor=#c0c0c0 height=27 vAlign=center align=left>Propeller Modification</TD><TD width=3></TD></TR><TR><TD height=970></TD><TD height=970 vAlign=top align=left>
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Although the installation and use of this procedure is well documented, we suggest caution. This is not the panacea for under powered boats. It can cause cavitation and prop blow out in some situations. A little experimentation is in order to achieve the desired results.
The hole size can be increased for certain applications. There have been applications with holes 1/2" and larger. Some have been cut at angles, some square, and some cut into the forward edge of the prop hub itself.
If by chance you do drill too large of a whole, you can retest with an epoxy patch, but once you have determined the correct size, take the prop to a prop shop so they can fill the hole back in with weld. Then re-drill to the correct size.
When testing be sure to try the prop under different speeds and conditions to verify satisfactory and safe operation.
Note: This procedure does not work with units with thru-transom exhaust.
It will work with Mercruiser's "Silent Choice System" ,
if left in the thru-prop under surface mode during take off.
Mercury's exclusive Performance Vent System (PVS) lets you adjust
your propeller to the way you boat.
Propellers currently available with PVS :
High Five, Laser II , Mirage Plus, Offshore,
Revolution 4, Tempest Plus, Trophy Plus
You don't boat the same way, with the same number of
people, under the same conditions every time. PVS propellers
are adjustable for changes in load and environment.
Mercury PVS propellers let you
choose how much ventilation is drawn out the vent
holes on the side of the prop. Propeller ventilation
makes a big difference in how your boat behaves.
Because nobody but you can tell when you hit that
perfect on-plane performance, PVS makes it easy for
you to adjust by simply changing the propeller's vent
plugs for optimum acceleration.
When your boat accelerates, exhaust is drawn
out of the vent hole located behind each
propeller blade. When the next blade strikes
this aerated water, it pushes through the aerated water easier than it would
through "solid" water. By controlling the amount of aerated water, you can pretty
much dictate how quickly your engine rpm rises. Once you're on plane, the water
flows over the vent holes and seals in the exhaust. This allows the propeller to
again operate in solid, non-aerated water.
Do I need the plugs in every time I boat and what if I lose one?
You don't need the plugs to operate your propeller normally. If the
plugs aren't in, the prop will just behave as if it has an extra-large vent. If
the conditions are right, you might even want to leave them out. And if you
lose one, they're easily available anywhere Mercury Propellers are sold.
Do I have to use the same plug size in each vent?
Not at all. Mix and match all you want, depending on the conditions.
Each vent can take any of the four plugs
at any time, without affecting the performance of the other vents.
How easy is it to change vent sizes?
It's a whole lot easier than changing propellers. The vents fit snugly
enough that you won't have to worry about them coming out, no matter
what the conditions. However, they're easy enough to remove and replace
when conditions change.
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All outboard and sterndrive using thru hub exhaust propellers
Poor acceleration on hard-to-plane boats.
Solution - Modify the propeller by drilling three 6mm (7/32") (see notes at bottom) holes "A" thru outer shell positioned as shown in the diagram. If there is a rib "B" under any of the proposed hole locations, use another propeller. Properly drilled, the holes will have no affect on top speed, maximum RPM, or ventilation in turns. Incorrect hole size or location will result in no improvement or in excessive ventilation, particularly in turns.
Drilling the holes allows exhaust gasses to bleed onto the propeller blades causing controlled ventilation during acceleration. This allows the motor to turn higher RPM under acceleration providing more power to plane the boat. Review the Diagnostic Procedures for additional items that will contribute to poor acceleration.
Diagnostic Procedure
The boat and motor should be inspected for the following conditions:
The boat and motor should be inspected for the following conditions:
· Transom should be at least recommended minimum height for motor installed. · Boat bottom must be clean and reasonably straight.
· Manual trim models should have angle adjusting rod positioned so motor may be trimmed down to a negative trim position when accelerating onto plane. If motor will not achieve negative trim, aluminum transom wedges should be installed between transom and motor.
· Manual trim models should have angle adjusting rod positioned so motor may be trimmed down to a negative trim position when accelerating onto plane. If motor will not achieve negative trim, aluminum transom wedges should be installed between transom and motor.
· Transom and boat bottom should be inspected for deterioration or weakness to assure they are not deflecting under acceleration.
· Propeller should be checked to assure it is undamaged, the correct type for the application and approximately the correct pitch.
· Check the boat for weight balance. Many times a slight change in position of fuel tanks, passenger seating, or other equipment will make an improvement in the boat's ability to plane. Move weight forward to help the boat plane more quickly.
· Check the engine synchronization linkage. Make sure the timer base is advancing properly, that the carburetors are opening at the same time, the throttle cam pick-up, the pick-up timing and full advance timing are correct.
· If the motor's performance seems marginal, check the full throttle RPM using a test wheel or dynamometer.
· Water test the boat to verify the condition. Use a shop tachometer to verify the full throttle RPM is correct for the model motor. Boats having acceleration problems should be propped to the upper end of the recommended operating range.
· To achieve good load carrying capability and top speed, the motor should be near the maximum rated horsepower of the boat.
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Although the installation and use of this procedure is well documented, we suggest caution. This is not the panacea for under powered boats. It can cause cavitation and prop blow out in some situations. A little experimentation is in order to achieve the desired results.
The hole size can be increased for certain applications. There have been applications with holes 1/2" and larger. Some have been cut at angles, some square, and some cut into the forward edge of the prop hub itself.
If by chance you do drill too large of a whole, you can retest with an epoxy patch, but once you have determined the correct size, take the prop to a prop shop so they can fill the hole back in with weld. Then re-drill to the correct size.
When testing be sure to try the prop under different speeds and conditions to verify satisfactory and safe operation.
Note: This procedure does not work with units with thru-transom exhaust.
It will work with Mercruiser's "Silent Choice System" ,
if left in the thru-prop under surface mode during take off.
Mercury's exclusive Performance Vent System (PVS) lets you adjust
your propeller to the way you boat.
Propellers currently available with PVS :
High Five, Laser II , Mirage Plus, Offshore,
Revolution 4, Tempest Plus, Trophy Plus
You don't boat the same way, with the same number of
people, under the same conditions every time. PVS propellers
are adjustable for changes in load and environment.
Mercury PVS propellers let you
choose how much ventilation is drawn out the vent
holes on the side of the prop. Propeller ventilation
makes a big difference in how your boat behaves.
Because nobody but you can tell when you hit that
perfect on-plane performance, PVS makes it easy for
you to adjust by simply changing the propeller's vent
plugs for optimum acceleration.
When your boat accelerates, exhaust is drawn
out of the vent hole located behind each
propeller blade. When the next blade strikes
this aerated water, it pushes through the aerated water easier than it would
through "solid" water. By controlling the amount of aerated water, you can pretty
much dictate how quickly your engine rpm rises. Once you're on plane, the water
flows over the vent holes and seals in the exhaust. This allows the propeller to
again operate in solid, non-aerated water.
Do I need the plugs in every time I boat and what if I lose one?
You don't need the plugs to operate your propeller normally. If the
plugs aren't in, the prop will just behave as if it has an extra-large vent. If
the conditions are right, you might even want to leave them out. And if you
lose one, they're easily available anywhere Mercury Propellers are sold.
Do I have to use the same plug size in each vent?
Not at all. Mix and match all you want, depending on the conditions.
Each vent can take any of the four plugs
at any time, without affecting the performance of the other vents.
How easy is it to change vent sizes?
It's a whole lot easier than changing propellers. The vents fit snugly
enough that you won't have to worry about them coming out, no matter
what the conditions. However, they're easy enough to remove and replace
when conditions change.
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