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Old 08-04-2017, 12:22 PM   #1
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Bayliner 4588 prop turn direction

I'm helping a friend with a late 70's 4588 regarding boat handling. It's got Hino's.

Besides me going out there and trying backing with each engine to determine which way she backs, does someone know? I guess they'd all have to be the same, but that seems likely.

Do both props turn the same way? Or counter? Which way does each side back?

TIA for any assistance!
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Old 08-04-2017, 02:22 PM   #2
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"Do both props turn the same way? Or counter? Which way does each side back?"

Gasoline engines can be had that turn opposite.

Diesels frequently use the gears in in the tranny for reverse rotation needs.

Sometimes the gears fwd and rev are slightly different ratios , hence the shaft tachometer.

The "proper " rotation is for the top of each prop to rotate to the boats CL, but lots of boats get it wrong.
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Old 08-04-2017, 03:04 PM   #3
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Thanks FF. I don't really think you got my question. When you put a transmission into reverse and the prop spins, there is an effect called prop-walk. I.e. in addition to the boat being "pulled backward" it is also directed to one side or the other.

With singles we use this to our advantage with "backing and filling."

So a single boat either "backs to port" or "backs to starboard."

I'm trying to see if someone already knows this regarding a bayliner 4588 with Hino's. Most likely the trannies spin the props the same way, like clockwise in forward, counter-clockwise in reverse.
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Old 08-04-2017, 05:00 PM   #4
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Most boats are right hand prop stbd, left hand on port. RH props back to port, LH to stbd. Not really an issue on a twin, you control backing direction not by the "walk" but by selecting engines.

RH prop spins CW when viewed from aft in fwd gear.
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Old 08-04-2017, 05:09 PM   #5
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Thanks FF. I don't really think you got my question. When you put a transmission into reverse and the prop spins, there is an effect called prop-walk. I.e. in addition to the boat being "pulled backward" it is also directed to one side or the other.

With singles we use this to our advantage with "backing and filling."

So a single boat either "backs to port" or "backs to starboard."

I'm trying to see if someone already knows this regarding a bayliner 4588 with Hino's. Most likely the trannies spin the props the same way, like clockwise in forward, counter-clockwise in reverse.


Bob, I think FF new exactly what you were saying.

As a single guy, I understand what you are asking. What they are saying is that the starboard and port engine props actually spin in opposite directions.

One of the effects of this is that the props counter each other as far as their tendency to create propwalk. So on a twin, if you put both engines in reverse, the stern won't tend to move to port as we are used to on our sailboats and single engine trawlers.
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Old 08-04-2017, 05:23 PM   #6
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Bob, I think FF new exactly what you were saying.

As a single guy, I understand what you are asking. What they are saying is that the starboard and port engine props actually spin in opposite directions.

One of the effects of this is that the props counter each other as far as their tendency to create propwalk. So on a twin, if you put both engines in reverse, the stern won't tend to move to port as we are used to on our sailboats and single engine trawlers.
Yes but what if you use only one engine in gear, i.e. reverse? That's what I'm trying to sort out. It makes sense the two would counter-rotate, otherwise you would have a huge walk one way or the other.

Seeing if we can take advantage of prop walk, just like we do on singles.

Guess we'll just go try it out. Thanks everyone.
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Old 08-04-2017, 06:41 PM   #7
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Tie the boat securely to the dock, start the vessel, and go into the engine room and observe the shaft rotation.
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Old 08-04-2017, 06:50 PM   #8
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Yes but what if you use only one engine in gear, i.e. reverse? That's what I'm trying to sort out. It makes sense the two would counter-rotate, otherwise you would have a huge walk one way or the other.

Seeing if we can take advantage of prop walk, just like we do on singles.

Guess we'll just go try it out. Thanks everyone.
Assuming the boat has the usual set up, the answer is in post 4 from Ski in NC. Maybe your posts crossed "in the mail".
To confirm, take the boat out in adequate water and try it, the result will be obvious.
Then try the stbd engine in fwd and port in reverse, at idle. The boat should spin on its axis.
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Old 08-04-2017, 07:11 PM   #9
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Assuming the boat has the usual set up, the answer is in post 4 from Ski in NC. Maybe your posts crossed "in the mail".
To confirm, take the boat out in adequate water and try it, the result will be obvious.
Then try the stbd engine in fwd and port in reverse, at idle. The boat should spin on its axis.
Yes Bruce, that certainly works on any twin. Not what I was after. I'm talking about a subtle "walk" to one side while reversing one engine. It's called prop walk. Sorry I wasn't able to articulate what I'm after.
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Old 08-04-2017, 07:20 PM   #10
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Yes Bruce, that certainly works on any twin. Not what I was after. I'm talking about a subtle "walk" to one side while reversing one engine. It's called prop walk. Sorry I wasn't able to articulate what I'm after.
Bob, we must be at cross purposes. I use "prop walk" all the time at close quarters, to rotate the boat as much or as little as I want, using either fwd or reverse, using one or other engine. I would not call it "subtle".
Are you talking about the whole boat moving sideways? There have been threads about that, it uses both engines and rudder, works on some boats and not others, and is reality or urban myth, depending on belief system.
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Old 08-04-2017, 08:33 PM   #11
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Originally Posted by JustBob View Post
Yes but what if you use only one engine in gear, i.e. reverse? That's what I'm trying to sort out. It makes sense the two would counter-rotate, otherwise you would have a huge walk one way or the other.

Seeing if we can take advantage of prop walk, just like we do on singles.

Guess we'll just go try it out. Thanks everyone.
Bob and twin engine boat that normally has counter rotating props won't have prop walk in the normal sense because the thrust on any one engine going astern or ahead will be acting asymmetrically. For example if your rudders are amidships and you go astern on your port engine it with no other forces acting on the vessel pull your stern to starboard. Go astern on your starboard engine and it will pull the stern to port.
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Old 08-04-2017, 08:47 PM   #12
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Bob, what people are trying to tell you is that there is no prop walk on a twin engine boat. If you use just ONE engine in reverse, it turns so dramatically that if there should be propwalk, it is not measurable in comparison to the rotation caused pulling the boat backward from one corner.
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Old 08-04-2017, 08:49 PM   #13
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Bob and twin engine boat that normally has counter rotating props won't have prop walk in the normal sense because the thrust on any one engine going astern or ahead will be acting asymmetrically. For example if your rudders are amidships and you go astern on your port engine it with no other forces acting on the vessel pull your stern to starboard. Go astern on your starboard engine and it will pull the stern to port.


Yup. One engine in forward or reverse would have a subtle precession effect, which is what I think Bob was wondering. However, as you point out the asymmetric nature of the offset prop will be so great as to overpower any prop walk induced.
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Old 08-05-2017, 05:17 AM   #14
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What creates prop walk is the difference in density of the water on the top blade and the bottom blade .

This allows the blade in denser water to pull in the direction it is being spun.

As boats with twin engines usually have smaller diameter props , the effect of just prop walk is less powerful.
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Old 08-05-2017, 06:27 AM   #15
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What creates prop walk is the difference in density of the water on the top blade and the bottom blade .

This allows the blade in denser water to pull in the direction it is being spun.

As boats with twin engines usually have smaller diameter props , the effect of just prop walk is less powerful.
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I haven't heard the density rationale before...can the density difference in that short a distance...the prop dia...be that significant?
Not trying to argue w those w a better understanding...just trying to understand it myself.

I was under the impression...maybe incorrect...that the affect of the closer proximity to the hull V at the top was a factor. Have also heard that is the reason props in tunnels produce little or no walk.
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Old 08-05-2017, 06:38 AM   #16
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Not a density difference, the density does not change measurably over the two feet of a prop. What does it is the wash from the top of the prop acts on the hull bottom while the wash from the bottom of the prob does not.
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Old 08-05-2017, 07:33 AM   #17
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True or false, on a twin putting the starboard engine in reverse will pull the stern to port regardless if you have a clockwise or counterclockwise prop setup when in forward gear.
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Old 08-05-2017, 11:28 AM   #18
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True or false, on a twin putting the starboard engine in reverse will pull the stern to port regardless if you have a clockwise or counterclockwise prop setup when in forward gear.


I would say False.

The stern will TURN to port, but that is a bit different dynamic than being pulled or pushed to port.

:-)
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Old 08-05-2017, 05:41 PM   #19
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The 45 Bayliner has prop pockets like my 38 and that limits prop walk to zero as far as I can tell. The 47 Bayliner doesn't have prop pockets but has a deeper draft.
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Old 08-05-2017, 06:52 PM   #20
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Bob, I'm apparently confused, too. There's no prop walk on a twin.

Both props turn outward in fwd as mentioned above. If you're only using one engine (no rudder), the side you're using dictates the direction the bow or stern will move.

If using Stbd only: fwd gear, bow to port; rev gear, stern to port. It will take rudder and a burst of power to move the bow to stbd in tight quarters.
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