Fishtailing outdrive

[Ryland3210]

I have heard that Mercruiser outdrives can oscillate back and forth at low speed with steering wheel held steady.
I am not sure whether there is any slack in the mechanism, but the issue continued even with a new outdrive.
It is a nuisance to constantly have to steer back and forth to try to prevent this. It's no fun coming into a marina as it is.

On motorcycles, the steering heads on many have a shock absorber type damping mechanism to prevent wobbling.
I wonder if this has been tried. I am tempted to adapt one with suitable stroke to my 28 foot single I/O Bayliner. I would use on with adjustable damping, like on my Moto Guzzi.
Any comments?
Thanks.

 

[Bt Doctur]

If the outdrive is physically moving and the steering cable is not, only a proper repair will fix it. Some boat hulls do wander and theres nothing you can do about it

 

[Ryland3210]

Aaaargh! Thanks. I guess I will have to get a buddy to help look for backlash while the boat is out of the water.

 

[Ryland3210]

I had a similar problem on an Old Searay, but it was caused by wear in the spline that connects the steering lever to the outdrive.

 

[alldodge]

I have heard that Mercruiser outdrives can oscillate back and forth at low speed with steering wheel held steady.
I am not sure whether there is any slack in the mechanism, but the issue continued even with a new outdrive.
It is a nuisance to constantly have to steer back and forth to try to prevent this. It's no fun coming into a marina as it is.

On motorcycles, the steering heads on many have a shock absorber type damping mechanism to prevent wobbling.
I wonder if this has been tried. I am tempted to adapt one with suitable stroke to my 28 foot single I/O Bayliner. I would use on with adjustable damping, like on my Moto Guzzi.
Any comments?
Thanks.

I don't think this is a steering issue, it is a common problem with a V-hull at slow speeds. A V-hull will wonder to port and starboard at idle speed. The amount of the wonder varies from how much depth the hull sits in the water.

To prove the issue, take the boat in a wide open area and let it start tracking. Once it starts to turn left it go, it will stop then come back the other way. If it turns more one way then the other, move the steering a slight bit more to the way which turns a bit less. Once you find this spot, this is your (what I call) wonder center location.

Now if your up on plane and you move the wheel and the turn is slow to react, you probably have play that needs to be fixed

 

[Ryland3210]

Thanks. That's a good test I can make with the boat in the water. When I am going slow, would it make sense to lower one trim tab to bias the hull in one direction and crab the boat somewhat?

 

[alldodge]

Tabs will have an effect, but for the most part, my single engine cruiser (with tabs) or runabout have not found much change. That said I have not tried to try the tabs in figuring it out

 

[Rick Stephens]

Adding tabs took a lot of the slow speed wander out of my boat. It used to go back and forth, I always figured it was picking a different, port or starboard, chine to follow. Back and forth. I added Smart Tabs, which are only adjustable on land. They took most of the wander away. For what it's worth, you should try a different depth on your tabs.

 

[Scott Danforth]

if your always on plane, there is no low speed wander.

 

[Bondo]

Thanks. That's a good test I can make with the boat in the water. When I am going slow, would it make sense to lower one trim tab to bias the hull in one direction and crab the boat somewhat?

Ayuh,.... Generally speakin', if the drive is tight, Less operator input cures the V-hull wonder,....

 

[Ryland3210]

I checked the backlash on the outdrive connection to the steering lever. It's pretty tight. At the prop, it will shift about 3/8" from left to right. The steering correction required is several times that. Next time I get a helper on the boat, I can look at what's happening to the steering lever when the wheel is rotated. The steering wheel has a rack and pinion actuating a cable to the steering mechanism. I'm not at the boat now to look, and excuse my ignorance, but can some one tell me if the steering is mechanical or hydraulic? It's a 2002 260 hp Mercuiser 5.7Liter EFI engine.

 

[Ryland3210]

Now that I think back, I do recall that the tabs had a huge effect on the fishtailing, but I don't recall whether it was worse with tabs up or down.

I do like the suggestion to stay up on plane. I'll need to practice to dive into the marina at 20 knots, slam the throttle to full reverse at the last second and stop just short of hammering the slip. If I can only perfect this maneuver, my marina buddies will certainly be impressed. LOL!

 

[alldodge]

You will be noticed for sure

 

[Ryland3210]

The steering cable friction got harder to deal with. The new one made steering much, much easier to steer with. It seems my replacing the power steering pump was a waste of time and money. The fishtailing problem is still there. Here are the results of my latest test: With engine running in neutral, I had my helper actuate the steering wheel back and forth. The rack and pinion at the helm has about 20 degrees of play. There is no means of adjusting the backlash.
The power steering servo valve controlling the tiller has about 1/4" of dead zone before it moves the tiller. I believe the hydraulic system allows the tiller to freely move by that amount before any resistance is provided by power steering.

Is that a normal amount of dead zone for the valve? Is a new valve indicated?
What about adding a device between the outdrive and transom with friction to hold the outdrive still? That was standard equipment on my '65 Harley to prevent steering head wobble, and it worked.

Thanks,,
Ryland

 

[alldodge]

You have 20 degrees of slop at the helm and 1/4 inch at the steering ram, that seems about normal for cable hydraulic steering. You get wonder it idle speeds and have to steer back n forth. Are you getting the same kind of wonder on plane?

 

[harleyman1975]

I cannot think of a boat that I have piloted that did not wander at displacement speeds.

 

[Rick Stephens]

I cannot think of a boat that I have piloted that did not wander at displacement speeds.

Me too. Even some fairly large ones. Smaller the boat, the more the chines seem to be able to bite and alternate the boat side to side. I found that if my drive is trimmed all the way down it lessens the wander a bit.

 

[Bondo]

What about adding a device between the outdrive and transom with friction to hold the outdrive still? That was standard equipment on my '65 Harley to prevent steering head wobble, and it worked.

Ayuh,.... As has been already asked,..... Do ya have any steerin' issues, while on-plane,..??

No matter how tight ya make the drive, a V-hull is gonna wander at displacement speeds,....
Less operator input is the cure,....
Yer floatin' on water, not drivin' a bike on blacktop,....
The blacktop is a static surface,.... Water is constantly movin',....

 

[achris]

I don't think this is a steering issue, it is a common problem with a V-hull at slow speeds. A V-hull will wonder to port and starboard at idle speed. ....

There's your answer. Post #3... I also have a deep V hull, with a brand new, tight as drive and steering linkages, wanders back and forth at sub-planing speeds... Very little you can do about it...

Chris........

 

[JoLin]

I cannot think of a boat that I have piloted that did not wander at displacement speeds.

Add me to the list. I think what the OP is experiencing is normal.

My .02