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!

"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.

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.

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.

JustBob said:

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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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.

dhays said:

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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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.

Tie the boat securely to the dock, start the vessel, and go into the engine room and observe the shaft rotation.

JustBob said:

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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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.

BruceK said:

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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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.

JustBob said:

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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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.

JustBob said:

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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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.

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.

Jetstream said:

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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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.

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.

FF said:

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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FF
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.

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.

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.

NewbieFromNJ said:

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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I would say False.

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

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.

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.

FlyWright said:

...If you're only using one engine (no rudder), the side you're using dictates the direction the bow or stern will move...

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Is this just semantics? Isn`t the result of using one engine prop walk? By doing that you lose the "cancelling out", you do it intentionally, to gain the benefits of prop walk to maneuver the boat.
And using one fwd and one reverse, isn`t that the ultimate use of prop walk to spin the boat on its axis? I sometimes add rudder, boat turns even tighter.

Prop walk or thrust

Twin engine boats have asymmetric thrust because of the prop offset from centerline. When only one engine is put in gear, with rudder parallel to the keel, the boat will carve an arc. The arc may be tighter in forward because prop is designed for forward thrust. If the engines are wide spaced the arc is tighter. If the boat has a deep keel, the arc will be longer. The prop that is not engaged creates a resistance to motion. Because of the trust and opposite side resistance, there is a projected location that becomes the pivot point of the arc and will be away from the boat itself. Each boat will be different in how fast it swings. My prop shafts are separated by 60”. It tracks like slot car with both props engaged. I need a counter rudder angle of over 20 degrees to track straight on one engine. That much asymmetric trust has nothing to do with prop walk.

Prop walk in a single is caused by the prop shaft being on an angle. That causes the acending blade to have less effective pitch than the decending blade. Therefore the decending blade has more bite on the water and pulls more than the acending blade. On twin engines with the engines being mounted outboard, the prop walk is not noticable since the prop is off center as some have noted previously.

BruceK said:

Is this just semantics? Isn`t the result of using one engine prop walk? By doing that you lose the "cancelling out", you do it intentionally, to gain the benefits of prop walk to maneuver the boat.
And using one fwd and one reverse, isn`t that the ultimate use of prop walk to spin the boat on its axis? I sometimes add rudder, boat turns even tighter.

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I don't thinks so Bruce. When the term prop walk is used I believe it's normally used in the context of the amount of sideways movement caused by a number of factors affecting an amount of side thrust on a single engine boat. I.e in a single engine boat with no other factors involved like wind or tide and the rudder amidships most single engine boats with the engine astern will tend to move the stern sideways one way or the other depending on the direction of prop rotation.

On a twin engine boat the small amount of side thrust from either prop at low speed going astern is completely offset by the fact that the thrust is offset from the vessels centre line (assymetric thrust). This will tend to pull the stern toward the opposite side from the engine that is in gear if only operating one engine.

Think of the extreme case. Your in open water in you twin engin boat with no current or wind and your rudder amidships. Put just your starboard engine astern and it will drag you around in circles to port. Put just your port engine astern and it will drag you around in circles to starboard. There is thrust acting on one side of the hull because it's offset from the centre line and only drag on the other side

The same will be true for one engine ahead but the circles will be much bigger because the thrust is acting on the hull so far aft on the hull and any sort of keel will tend to keep the vessel going straighter ahead.

With one engine ahead and one astern it is the ultimate use of assymetric thrust to turn although the ahead engine will always be slightly more efficient that the astern engine because of the design of the prop.

Just my 2 cent worth,

Brett

Thanks Brett. I will use "asymmetric thrust" "going forward"(and back, and around..). If I get the maneuverability I`ve enjoyed, it`s all good.
Remember the old saying"Call me anything you like, but don`t call me late for dinner". Seriously, I appreciate the help and careful explanations, and hope the OP gets his boat sorted.

Once the OP learns the rotation of his engines/shafts/props, I recommend going below and using a Marks-a-Lot to draw arrows on each engine indicating their rotation (in Forward).

JustBob said:

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!

Click to expand...

Hello - We have owned two 4588 Bayliners and one 4788.

- The props spin counter to one another with the stb prop turning clockwise in fwd when viewed from the stern.
- The boat can be 'walked' with the props due to their horizontal angle of attack on the water , the degree of walk on the 45 is subdued due to the partial prop tunnel and partial keel but is still vey usable.
- The 4588 Bayliner was not produced until 1984 so the boat cannot be a late 70's boat. The hull number impressed onto the stb stern hull will identify the date and location of manufacturing.

smitty477 said:

Hello - We have owned two 4588 Bayliners and one 4788.

- The props spin counter to one another with the stb prop turning clockwise in fwd when viewed from the stern.
- The boat can be 'walked' with the props due to their horizontal angle of attack on the water , the degree of walk on the 45 is subdued due to the partial prop tunnel and partial keel but is still vey usable.
- The 4588 Bayliner was not produced until 1984 so the boat cannot be a late 70's boat. The hull number impressed onto the stb stern hull will identify the date and location of manufacturing.

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DING DING DING! We have a winner. Thank you Smitty477 for answering my original question. Sorry about the year, I guess the 70's were a bit of a blur?

JustBob said:

DING DING DING! We have a winner. Thank you Smitty477 for answering my original question. Sorry about the year, I guess the 70's were a bit of a blur?

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You can find a lot of detailed information on these boats and a bunch of current owners at the site: baylinerownersclub (dot) org.
Posting in the motor yachts section there will yield the best results for this boat, or perhaps just review the posts there.