Left hand prop?
- Thread starter Jongleur
- Start date
Jong,
I don't understand your question. Do you have a right-hand prop on now?
I believe the Universals are all for left-hand props. My 3M20A has a LH prop.
I would assume you already have a LH prop, if not your boat would not move forward in gear. If backing up with straight rudder, your boat w/LH prop should walk the stern to port.
Here's a more in-depth explanation:
“Prop Walk” and Maneuvering Around The Marina
One of the trickiest parts of sailing doesn’t have anything to do with sailing. It has to do with motoring around the marina. This includes backing out of a slip, shifting into forward gear after backing out of the slip, and motoring back to the slip. For new sailboat owners, successfully backing out of a slip may be the trickiest and toughest part to boat ownership.
The reason that backing out of a slip is so tough is because sailboat engines are notoriously underpowered; AND the propellers are also very small compared to the size and weight of the sailboat. Compare for example a twenty-five foot long powerboat and its fifty to two hundred horse-power engine and huge propeller with a twenty-five foot sailboat with its six to ten horse-power engine with its “tiny” propeller. The “tiny” propeller doesn’t move much water with each revolution…… BUT, the propeller can “walk” the stern of the boat to the left or to the right before the boat begins moving either forward or backward.
We talk about the propeller being either “left handed” or “right handed”. This refers to the rotation of the propeller when in forward. If the boat is not moving and the propeller begins to turn, the rotation causes the propeller to “paddle-wheel” and move the stern of the boat to one side or the other. A “right hand” propeller tends to walk (prop walk) the stern to the right (starboard) in forward; and to the left (port) in reverse.
CR
I don't understand your question. Do you have a right-hand prop on now?
I believe the Universals are all for left-hand props. My 3M20A has a LH prop.
I would assume you already have a LH prop, if not your boat would not move forward in gear. If backing up with straight rudder, your boat w/LH prop should walk the stern to port.
Here's a more in-depth explanation:
“Prop Walk” and Maneuvering Around The Marina
One of the trickiest parts of sailing doesn’t have anything to do with sailing. It has to do with motoring around the marina. This includes backing out of a slip, shifting into forward gear after backing out of the slip, and motoring back to the slip. For new sailboat owners, successfully backing out of a slip may be the trickiest and toughest part to boat ownership.
The reason that backing out of a slip is so tough is because sailboat engines are notoriously underpowered; AND the propellers are also very small compared to the size and weight of the sailboat. Compare for example a twenty-five foot long powerboat and its fifty to two hundred horse-power engine and huge propeller with a twenty-five foot sailboat with its six to ten horse-power engine with its “tiny” propeller. The “tiny” propeller doesn’t move much water with each revolution…… BUT, the propeller can “walk” the stern of the boat to the left or to the right before the boat begins moving either forward or backward.
We talk about the propeller being either “left handed” or “right handed”. This refers to the rotation of the propeller when in forward. If the boat is not moving and the propeller begins to turn, the rotation causes the propeller to “paddle-wheel” and move the stern of the boat to one side or the other. A “right hand” propeller tends to walk (prop walk) the stern to the right (starboard) in forward; and to the left (port) in reverse.
CR
Last edited:
Rpell,
The orig. question was abit confusing, that's why I sent him the definition.
I don't understand why Jong asked about changing to a LH prop.
Maybe he will elaborate........
CR
The orig. question was abit confusing, that's why I sent him the definition.
I don't understand why Jong asked about changing to a LH prop.
Maybe he will elaborate........
CR
captnron:
Here's an answer I gave on C&S forum:
Yes, good questions. I have read some literature.
The mechanic that checked out the motor said the
shaft is spinning left handed while in what he said
should be "forward" for this engine and trans, but it
has a right handed prop on. I asked a diesel mechanic
and they said this diesel rotates "left handed".
Yes, the linkage is connected "backward". Yes, it
has a Hurth transmission.
I recently bought the boat from the original
owner who is not able to answer any questions.
Yes, it is a re-power, apparently from an Atomic
4 to the M25XP somewhere in the 1980s or 1990s.
Backs up well but going ahead is for squat.
That's why it's so confusing.
Here's an answer I gave on C&S forum:
Yes, good questions. I have read some literature.
The mechanic that checked out the motor said the
shaft is spinning left handed while in what he said
should be "forward" for this engine and trans, but it
has a right handed prop on. I asked a diesel mechanic
and they said this diesel rotates "left handed".
Yes, the linkage is connected "backward". Yes, it
has a Hurth transmission.
I recently bought the boat from the original
owner who is not able to answer any questions.
Yes, it is a re-power, apparently from an Atomic
4 to the M25XP somewhere in the 1980s or 1990s.
Backs up well but going ahead is for squat.
That's why it's so confusing.
Jong,
I stand corrected, Rpell was correct that all the Universal engines turn clockwise & They use a RH prop rotation. I hadn't changed out my prop in 15 years. Left hand stuck in my last two brain cells.
So, why would you want to change to an opposite hand prop? The correct RH prop should already be on your boat. If you're questioning performance, the trick is in changing the prop pitch.
The simple rule is: tied at the dock or underway:
If your engine @ max throttle exceeds the manufacture's max RPM's, you're are under pitched. If your engine cannot achieve max RPM, you're overpitched. A prop shop can then help you in selecting a proper prop.
CR
I stand corrected, Rpell was correct that all the Universal engines turn clockwise & They use a RH prop rotation. I hadn't changed out my prop in 15 years. Left hand stuck in my last two brain cells.
So, why would you want to change to an opposite hand prop? The correct RH prop should already be on your boat. If you're questioning performance, the trick is in changing the prop pitch.
The simple rule is: tied at the dock or underway:
If your engine @ max throttle exceeds the manufacture's max RPM's, you're are under pitched. If your engine cannot achieve max RPM, you're overpitched. A prop shop can then help you in selecting a proper prop.
CR
Here's what I've found so far: On C&F forum,
someone found the Hurth transmission manual
and I downloaded it and read up on them.
I posted this on C&F:
Okay. It's getting close to midnight here and
I am actually having fun reading the Hurth
transmission manual. Can't put it down. Learning
a lot.
So, best guess is that there is no necessarily
right or wrong forward or reverse direction.
That reasoning is from the manual using "A" and
"B" for running one way or the other, not "forward"
and "reverse".
Also, as Jim noticed, the ratios are all over the
board. Some, the "A" ratio is higher and some
the "B" ratio is higher. It seems you would just
choose that tranny that most closely meets
your needs.
I'm also guessing that with different ratios,
the torque available at different speeds is
different, so you make a decision based on
that also. Higher torque, high speed or higher
torque, low speed? Seems one would have
to try different prop pitches and different
handedness to come to any conclusions.
Though I think someone must have calculated these
all out and that information would be valuable
to someone like me trying to figure out what
to do. I wonder where that info is?
Thanks again. Knowledge is power...diesel power.
__________________
someone found the Hurth transmission manual
and I downloaded it and read up on them.
I posted this on C&F:
Okay. It's getting close to midnight here and
I am actually having fun reading the Hurth
transmission manual. Can't put it down. Learning
a lot.
So, best guess is that there is no necessarily
right or wrong forward or reverse direction.
That reasoning is from the manual using "A" and
"B" for running one way or the other, not "forward"
and "reverse".
Also, as Jim noticed, the ratios are all over the
board. Some, the "A" ratio is higher and some
the "B" ratio is higher. It seems you would just
choose that tranny that most closely meets
your needs.
I'm also guessing that with different ratios,
the torque available at different speeds is
different, so you make a decision based on
that also. Higher torque, high speed or higher
torque, low speed? Seems one would have
to try different prop pitches and different
handedness to come to any conclusions.
Though I think someone must have calculated these
all out and that information would be valuable
to someone like me trying to figure out what
to do. I wonder where that info is?
Thanks again. Knowledge is power...diesel power.
__________________