Tightening the motor steering

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dralyagmas
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Tightening the motor steering

Post by dralyagmas » May 2nd, '11, 10:48

Hi

I have a 5hp Mercury (2008) and I want to tighten the ability for it to be able to turn. ie: I want to make it harder to turn so when the boat is motoring I can steer with the rudder without the motor slowly turning due to vibration.

Is this possible?

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Tez
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Re: Tightening the motor steering

Post by Tez » May 2nd, '11, 11:03

Our OB has a lever about 100mm long that comes out from the top of the pivot - under the powerhead - it seems to work like a cam on the pivot so that the further to the left, the tighter the pivot becomes... at it's limit, the pivot is locked solid. I generally have it set so that I can turn the OB, but there is a measure of resistance.

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Tez
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Re: Tightening the motor steering

Post by The Baz » May 2nd, '11, 11:46

My 2006 8hp Merc has a spring loaded bolt protruding from the shaft that can be tightened to stiffen up the steering movement. Have a look yours should have one too.
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Furstin
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Re: Tightening the motor steering

Post by Furstin » May 2nd, '11, 11:52

The merc /tohy 5 has a butterfly screw on the right hand side of the leg (facing the motor). Tighten it up and it should stop it rotating mostly, but at idle it still moves a bit - you have to have it done up really tight.
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Re: Tightening the motor steering

Post by INMA » May 2nd, '11, 12:58

I have the same outboard and eventually the friction system completely stopped working.

At the next service (when I got home, I do my own work) I pulled the 4 bolts that hold the leg in the bracket off and removed the bearing cap to look at the setup.

I discovered that at manufacture there was virtually no grease put on the bearing areas and the thumb screw that pushes the brake bit was siezed and had never been lubricated.

So I freed up the thumb screw and added some grease to the thread, greased all the sliding surfaces and put it back together as it was designed to go together, no mods just grease.

Since then my friction thing works fine and if it turns at idle I just tighten the thumb scew a bit and it holds reasonably well.

Its a very easy job to copy what I did. Tilt the engine in the bracket, undo the 4 bolts, add grease and replace the four bolts. It would be nice to have an extra pair of hands to make sure the leg does not fall out of the bracket but otherwise it was a very simple job that almost anyone could do.

I used ordinary car grease and figured I will do it again in a few years. I also greased the grease nipples but they do not put grease where its needed for the friction adjustment.
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Re: Tightening the motor steering

Post by Ukuri » May 3rd, '11, 09:33

Rather than tightening up the clamp to stop it wandering under power why not try fitting some type of linkage to connect it to the tiller so that it turns when you turn the tiller. I had exactly the same issue as you describe no matter how much I tightened up the clamp. A big stink boat would go by and the wash would toss me around throwing the OB off line a little and before long the OB is pointing 30 or 40 degrees offline.

As I have the rest of the week off and will be hoping to get in a sail with some wind I will take some pics of what I have done and what some of the others at WMYC have done and post them. I started do do some sort of a sketch to explain the way you work out the dimensions so that both the tiller and OB turn at the same rate but it is probably easier to just take a few pics and post them.

Cheers
Chris

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zebedee
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Re: Tightening the motor steering

Post by zebedee » May 3rd, '11, 14:19

Ukuri wrote:As I have the rest of the week off and will be hoping to get in a sail with some wind I will take some pics of what I have done and what some of the others at WMYC have done and post them. I started do do some sort of a sketch to explain the way you work out the dimensions so that both the tiller and OB turn at the same rate but it is probably easier to just take a few pics and post them.
I looked at this a long time ago and gave up, so you've inspired me to have a proper look at the problem. I've drawn up some diagrams in AutoCad.

OK first up we have a top view of a boat to help you get your bearings:
Image
Note the outboard mounted on a bracket to port, pivoting on a point which is inconveniently further back than the rudder pintles.
Pivot points are represented by very small circles.

Now I am sure you can all see that if the linkage between the outboard and the rudder is not at the same radius from each pivot point, the two will not remain parallel. It may be that this is a good thing; you might want the outboard to turn further than the rudder, but to keep things simple I've put a short strut out the back of the rudder to connect the linkage to. So here's the obvious way to set up a linkage:

Image

Obviously this is just a model, so the units don't really mean anything, but I had in mind inches as I drew the diagrams. The linkage fixes to the outboard at a distance of 25 (inches if you wish) from the outboard pivot, and to the rudder at a distance of 25 from the rudder pintles.

With the outboard and the rudder parallel, the linkage length turns out to be 31.8277 (inches?)! It's important to build boat parts accurate to 0.1 thou! :D I'll leave that label on the linkage in all the following diagrams.

OK, lets see what happens when we steer to starboard with this linkage:

Image
Image

The rudder and outboard stay nicely parallel - it looks good!

And to port:

Image

So far so good...

Image

Yep, that's good!

Or is it?

Lets look more closely at that point where teh linkage lines up with the rudder and outboard...

Image

And what happens around this point:

Image
Image

Oh that's ugly...

It was about this stage that I gave up when I first looked at this idea since my outboard is so far behind my rudder.
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zebedee
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Re: Tightening the motor steering

Post by zebedee » May 3rd, '11, 14:42

zebedee wrote:Image

Oh that's ugly...

It was about this stage that I gave up when I first looked at this idea since my outboard is so far behind my rudder.
This is called going "over centre". Sometimes it is a good thing, it is useful for latches, etc, but for steering linkages it is bad.

But wait, what happens if we put the rudder and outboard next to each other? can we make that work? Is there a way to put them next to each other without having to move the outboard bracket or put the rudder pintles on extensions?

At this point a little lateral thinking is needed. If you can't move the outboard, and you can't move the rudder...

Move the boat:

Image

Lets see how this linkage works as we approach the extreme points of operation:

Image
Image
Image
Image

It works well. And it will work well with different length pivot arms, even "negative" length arms which project out the other side instead:

Image
Image
Image

The basic principles are:
1) To keep the outboard and rudder parallel:
- the linkages must be the same length (that 25 dimension in the first diagram) and the strut joining them must be the same length as the distance from the outboard pivot to the rudder pivot.

1a) To make the outboard turn more:
- Make the outboard linkage shorter than the rudder linkage.

2) To avoid over centre problems:
- the linkages on the outboard and the rudder must be perpendicular to a line from the rudder pivot to the outboard pivot when everything is pointed straight ahead.

If anyone is interested in unequal length linkages to steer the outboard tighter than the rudder, I can knock up a model and post it here, but its time I did something useful this afternoon. Bye!
A man's boat is his Castle. The Gippsland Lakes are my moat. Castle 650 #10, Roller Coaster.

Ukuri
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Re: Tightening the motor steering

Post by Ukuri » May 5th, '11, 23:47

As promised here are a few pics of the set up on the Careel. The OB is mounted on the transom and the OB pivot point is only a little further out from the transom than the rudder gudgeon so it is a little simpler than trying to fit a coupling if have an OB raising bracket.
IMAG0105 Mini.JPG
This shows the adjustable coupling in position
IMAG0105 Mini.JPG (34.6 KiB) Viewed 3154 times
It is attached to the rudder box using a simple drop in pin so it is quick to remove as it must be disconnected to tilt the OB.
IMAG0107 Mini.JPG
Another view of coupling in place
IMAG0107 Mini.JPG (39.61 KiB) Viewed 3154 times
It is constructed using a $10.00 6mm Bottle screw that was cut in half and then I silver soldered a length of 7mm Stainless Rod into each half to lengthen it.
IMAG0110 Mini.JPG
Connection on rudder end. A bit blurry but the tape shows that the dimension from the rudder pintle to the connection point is 315mm
IMAG0110 Mini.JPG (31.02 KiB) Viewed 3154 times
IMAG0111 Mini.JPG
This is a blurry close up of the connection showing the distance from the centre of the OB pivot to the connection is also 315mm
IMAG0111 Mini.JPG (27.32 KiB) Viewed 3154 times
The important thing to remember is that you are trying to create a parallelogram out of the two connection points and the two pivot points. My OB is much longer front to back than my rudder box so it determined the length of 315 mm. To extend the rudder box I used a short length of 25 x 25 x 3 aluminium "T" section that I had lying around. I didn't like the idea of drilling holes in the OB as it's still under warranty so I just bent up a bracket out of some 80 x 3 mm aluminium flat bar that I bought to make up something else.
IMAG0112 Mini.JPG
Bracket on the rudder box
IMAG0112 Mini.JPG (35.54 KiB) Viewed 3154 times
IMAG0113 Mini.JPG
Bracket on the OB
IMAG0113 Mini.JPG (29.73 KiB) Viewed 3154 times
As I am only allowed to include 6 attachments then I will post this and complete it in a subsequent post.

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Re: Tightening the motor steering

Post by Ukuri » May 6th, '11, 00:13

Cont.
IMAG0114 Mini.JPG
Another view of the OB bracket.
IMAG0114 Mini.JPG (35.89 KiB) Viewed 3152 times
To turn hard to Stbd the coupling had to go under the OB and bracket hence the "Z" shape. To connect it to the OB I simply replaced two of the bolts that fix the powerhead to the leg with longer ones.
IMAG0115 Mjnj.JPG
Control arm restricting travel to Stbd.
IMAG0115 Mjnj.JPG (57.54 KiB) Viewed 3152 times
IMAG0116 Mini.JPG
Raising the control arm to get full travel to Stbd.
IMAG0116 Mini.JPG (55.32 KiB) Viewed 3152 times
To get full travel to Stbd. it is necessary to lift the control arm. However to get full travel to Port it needs to be dropped. Is a bit of a PITA when docking, especially when using fwd and rev and swinging the tiller one way then the other to sneak onto the pontoon between moored boats but I am getting more proficient at it. There is a position for the control arm somewhere between up and down where I can get good travel both ways but there is not much room for error as the transom cut out in the careel was apparently designed for a Seagull and the Honda is a bit bloated for a 5hp motor.
IMAG0117 Mini.JPG
Full travel to Port requires the arm to be down or it fouls on the rudder box.
IMAG0117 Mini.JPG (57.06 KiB) Viewed 3152 times
Below are a couple of pics of a set up on a Ross 780 with the OB on a lifting bracket using 22mm Alum tube and plastic canopy fittings.
IMAG0120 Mini.JPG
Ross 780 set up
IMAG0120 Mini.JPG (37.54 KiB) Viewed 3152 times
IMAG0121 mini.JPG
Ross 780 set up
IMAG0121 mini.JPG (43.82 KiB) Viewed 3152 times
The load on the connection is not very high so the plastic canopy fittings are adequate. The important thing to remember is that the OB must be disconnected before tilting it.

Cheers
Chris

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dralyagmas
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Re: Tightening the motor steering

Post by dralyagmas » May 6th, '11, 10:39

Alright guys while this stuff looks great, my boat is a race boat which I am not keen on rigging this type of system on.

I have been looking through the web for the details on how to lubricat ethe pivot friction assembly and will take a grease gun to my motor today and see what happens.

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