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Old 12-11-2017, 08:34 AM   #1
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Replacing Prop with left prop

All,

I'm thinking of replacing my right hand prop with a left hand prop so that the boat will walk to starboard instead of port in reverse.

This is to solve a tight turning issue in getting the boat out of it's slip.

Is there anything more than simply replacing the prop and changing the engine controls so reverse is forward and forward is reverse?
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Old 12-11-2017, 09:04 AM   #2
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You should look at the ratings on your transmission. Many, but not all, transmissions have different gear ratios for reverse and forward. If yours has different ratios and ratings then your suggestion won't work.
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Old 12-11-2017, 09:10 AM   #3
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To answer this, need to know what trannie you have. Older velvet drive- nope, reverse is dedicated. HBW or ZF or Twin Disc- can swap rotation.

Post what gear you have.
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Old 12-11-2017, 12:11 PM   #4
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You realize that that making it walk backwards in one direction isn’t the only changes you’ll get?

Does your starboard engine turn the same as the port?

Are you certain that you couldn’t overcome this issue with practice?
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Old 12-11-2017, 12:41 PM   #5
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.....

Does your starboard engine turn the same as the port?

Are you certain that you couldn’t overcome this issue with practice?
I believe the OP has a single. He wouldn't be having a prop-walk issue with twins. He has a bow thruster, however I can't recall, but believe he has a sternthruster.

If I recall from previous posts that he has a narrow channel with a bank on one side and a seawall on the other and needs to back down a decent length to depart his slip.

It's interesting since my Mainship 350 single backs to Stbd.
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Old 12-11-2017, 01:07 PM   #6
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I walk to stbd also, LH prop and wouldn't want it any other way as I single hand and it helps a lot docking. I always wondered why some singles are LH and some are RH. Hopefully someone on this thread will enlighten us all :-)
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Old 12-11-2017, 01:33 PM   #7
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I doubt Seevee has a Borg Warner Velvet drive as we do but here's what our manual says:

Caution: Early gear failure will occur when the transmission must be operated in reverse to obtain forward when operated with a propeller having the wrong hand of rotation.
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Old 12-11-2017, 01:41 PM   #8
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A good number of reduction gears like my ZF 280 use one gear set in "A" direction, and use two gear sets in "B" direction. So a little less friction and wear in "A" direction. With a std rotation engine (CCW as viewed at flywheel end), "A" direction is reversed from engine so it is a RH prop.

So a tiny preference for RH props on singles. If you want your walk to stbd, then nothing wrong with going LH.
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Old 12-11-2017, 02:38 PM   #9
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Quote:
Originally Posted by Shrew View Post
I believe the OP has a single. He wouldn't be having a prop-walk issue with twins. He has a bow thruster, however I can't recall, but believe he has a sternthruster.

If I recall from previous posts that he has a narrow channel with a bank on one side and a seawall on the other and needs to back down a decent length to depart his slip.

It's interesting since my Mainship 350 single backs to Stbd.
While prop walk isnt an issue with twins, prop walk does exist and is very useful on twins when correct.
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Old 12-11-2017, 02:55 PM   #10
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Originally Posted by Ski in NC View Post
A good number of reduction gears like my ZF 280 use one gear set in "A" direction, and use two gear sets in "B" direction. So a little less friction and wear in "A" direction. With a std rotation engine (CCW as viewed at flywheel end), "A" direction is reversed from engine so it is a RH prop.

So a tiny preference for RH props on singles. If you want your walk to stbd, then nothing wrong with going LH.
Ski,

Good info, thx. Mine is a ZF 80-1 A, Ratio I = A= 2.50 B= 2.50. I'm not sure what the A and B mean, different directions?

I called ZF and they will get back to me.

Other than the transmission, just assume I could change the engine controls at the engine control box?
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Old 12-11-2017, 02:57 PM   #11
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I walk to stbd also, LH prop and wouldn't want it any other way as I single hand and it helps a lot docking. I always wondered why some singles are LH and some are RH. Hopefully someone on this thread will enlighten us all :-)
If you had a rh prop you’d just land on the port side.

But I think the LH prop and landing on the stbd side is common because of the right of way issues that promotes the builders and others to put the helm on the stbd side.
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Old 12-11-2017, 03:00 PM   #12
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While prop walk isnt an issue with twins, prop walk does exist and is very useful on twins when correct.
Agreed. Working prop-walk in your favor by 'tractoring' a twin-engine vessel is wonderful. Twins were initially on my 'must-have' list prior to buying my current boat. It was the the 'one' big compromise I gave in on.
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Old 12-11-2017, 03:01 PM   #13
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Originally Posted by Xsbank View Post
You realize that that making it walk backwards in one direction isn’t the only changes you’ll get?

Does your starboard engine turn the same as the port?

Are you certain that you couldn’t overcome this issue with practice?
X,

Single engine. I don't think practice would work. I've tried it several times, and without a wind will work fine. But the wind is impossible to turn into enough to get the bow around without a LOT of effort (and space). And I just don't have the space.

I'm gonna get my drone out an take a pic of turning this thing around. Perhaps I'll get some good ideas from the folks here.

I wanted to boat out Saturday, crosswinds at 15 to 20 knots, tide was fairly low. Even turning to starboard which the prop favors would have been too dicey and didn't have enough water to get the stern far enough from the docks to make the turn so I cancelled.

If I could turn to port (left hand prop required) the bow would have been in the shallow water giving more room to make the last swing with the wind blowing it around, which would have been easy vs. less room fighting the wind trying to work the bow against the wind.
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Old 12-11-2017, 03:04 PM   #14
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The more I think about it, the more it seems odd that the MS400 is prop-walking to Port. The Lower Helm and lower helm door are both to Stbd. I back to Stbd. Using the 'bump and fill' technique it makes it so Stbd is the preferred side to dock on. Backing to Port would make the port side the more favorable side to dock on, however that makes stepping out to the midship cleat from the lower helm on the wrong side of the boat.

I'm surprised that MS designed the 400 like that.
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Old 12-11-2017, 03:55 PM   #15
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...crosswinds at 15 to 20 knots, tide was fairly low. Even turning to starboard which the prop favors would have been too dicey...
Good call. Every boat has limits in crosswind departures/landings.

Bow thruster. $5-7K. You will get a lot more usage of your boat
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Old 12-11-2017, 04:02 PM   #16
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X,

Single engine. I don't think practice would work. I've tried it several times, and without a wind will work fine. But the wind is impossible to turn into enough to get the bow around without a LOT of effort (and space). And I just don't have the space.

I'm gonna get my drone out an take a pic of turning this thing around. Perhaps I'll get some good ideas from the folks here.

I wanted to boat out Saturday, crosswinds at 15 to 20 knots, tide was fairly low. Even turning to starboard which the prop favors would have been too dicey and didn't have enough water to get the stern far enough from the docks to make the turn so I cancelled.

If I could turn to port (left hand prop required) the bow would have been in the shallow water giving more room to make the last swing with the wind blowing it around, which would have been easy vs. less room fighting the wind trying to work the bow against the wind.
I would presume you know how to "back and fill" (Google/Youtube) and have determined it won't work for you. I have used it in some pretty nasty stuff with my AT34.

Goosing the throttle (hard) for just a second or two with the helm hard over had some pretty dramatic shifts in my boat - the stern would feel like it was lifting up and setting back down 5-7ft over from where it was. Some bursts of throttle in reverse to keep position, then do it again. And again. And again.
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Old 12-11-2017, 07:34 PM   #17
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Ski,

Good info, thx. Mine is a ZF 80-1 A, Ratio I = A= 2.50 B= 2.50. I'm not sure what the A and B mean, different directions?

I called ZF and they will get back to me.

Other than the transmission, just assume I could change the engine controls at the engine control box?
Seevee,

You couldn't have a better transmission to use for your project. I have a brochure for the ZF 80 A Series which states: "Suitable for twin engine installations (same torque capacity in ahead or astern mode. Reduction Ratios in ahead or astern are very close). In your case, the ratios are identical.

My ZF gearboxes operate just as Ski detailed a couple of posts earlier, so go ahead and reverse the prop and shift cables. Also, if it were mine, I would change the gear lube and filter too, just in case the wear patterns change for the clutch packs, bearings, gears etc. you'll have the best lubrication possible.

Finally, this would be a great opportunity to make any pitch adjustment to the new prop if needed to get the right WOT engine speed etc.
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Old 12-11-2017, 07:41 PM   #18
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I think the shift cable just needs to be swapped within the control head , no? In other words, the other arm on a Morse or Kobelt?
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Old 12-11-2017, 07:46 PM   #19
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I would presume you know how to "back and fill" (Google/Youtube) and have determined it won't work for you. I have used it in some pretty nasty stuff with my AT34.

Goosing the throttle (hard) for just a second or two with the helm hard over had some pretty dramatic shifts in my boat - the stern would feel like it was lifting up and setting back down 5-7ft over from where it was. Some bursts of throttle in reverse to keep position, then do it again. And again. And again.
Boathealer,

Yes, I've practiced this maneuver with this boat, and it responds fairly well. However, going thru the point of 90d to the wind, one cannot stop the wind from blowing it sideways somewhat. at 15 knots that's 5 feet per second. Now the boat won't move that fast but could easily go a foot per second. And the big winds are always toward the docks.

I've got about 50 feet to turn a 40 ft boat (about 45 feet with the pulpit). And the bow is between some docks in the middle of the turn. That's just not enough margin without a better plan.

With the bow pointing toward the wind, the bow goes over the shallow water, giving at lease another 10 to 20 feet depending on tide, which is a huge advantage. Plus, powering from the stern the boat may walk down the canal a bit with high winds but can keep it off the docks, and when the bow starts to swing down wind, all I have to do is power up and head out.

With tide up or wind straight up or down the canal, no issue.
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Old 12-11-2017, 07:47 PM   #20
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Quote:
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The more I think about it, the more it seems odd that the MS400 is prop-walking to Port. The Lower Helm and lower helm door are both to Stbd. I back to Stbd. Using the 'bump and fill' technique it makes it so Stbd is the preferred side to dock on. Backing to Port would make the port side the more favorable side to dock on, however that makes stepping out to the midship cleat from the lower helm on the wrong side of the boat.

I'm surprised that MS designed the 400 like that.
Totally agree. The Mainship has a lot of shortcomings, but all boats do. What I like about the Mainship is that it's simple, spacious and has a lot of nice features that a lot of boats just don't have. Stairs not ladders, French doors, not sliding, reasonable cockpit, swim platform door on side, walk way around the whole boat, overhang on both side, nice for rain and sun and nice for kayak storage and windsurfers, large engine room, large flybridge with nice aft area, And relatively easy to fix.

Prop should have favored the starboard side. Now, 99% of the time I still dock to starboard, with little issue... but in a wind I might work a bit harder.
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