Toe in or out for more forward torque

They run a workboat at our marina.

The motors are toed in.

When they push boats on the bow of the workboat; they have poor maneuverability.

I told them to toe out.

Is my advice sound? The motors are tied with a bar that also limits their travel a bit more than full.

 

It depends! Seriously, it depends on the boat and its job.
Doubt if one of them has a counter-rotating prop but some applications favor switching them from conventional orientation.
I'd mark the tiebar and try different settings.
Good luck.

 

Nope. Same direction spin

 

If they want maneuverability, a joystick system that steers the motors separately is the best. How are they tying the boats to the bow? With barges, the tug gets secured very tightly.

 

Engines in twin screw boats more properly have what we call "splayed" shafts, as in when looking in plan view the transmission couplings are closer together than the shaft logs.
I suppose that with outboards we might call that "toe in".
It relieves the "hunting effect" in the steering, the boat has a better tendency to want to go in a straight line.

 

Toe in or out for more forward torque (Header)

By torque you are refering to the torque that the engine thrust will create wrt to the hull to increase steering ability?

How many degrees of toe in would you suggest to incorporate?

In any case, it should not make any difference if toed in or toed out

Why would you think that toed in or out would make a difference?

 

Toe out will increase how sensitive the steering torque is to differential throttle. It can be quite noticeable if you are throttle steering up a channel. But it doesn't change anything with the steering wheel. It won't have a noticeable effect in close-quarters maneuvering. Looking at it, it doesn't surprise me that it is a challenge to handle.

 

My experience with my twin engine boat that came from the dealer with a small amount of toe-out was awful. Could not hold a straight line, I thought something was wrong with the steering. 3/16" toe-in cured it completely.
A different hull will have its own needs.

 

To explain a bit further:
Twin screw boats, for good maneuverability, (besides a little "toe in",) need to have their steering geometry set up with what we call in automotive language "Ackerman steering".
The further apart the props, (shafts or outboards,) the more need for it.
As a boat turns the inside prop on an outboard, (or rudder on an inboard.) travels thru a smaller radius in the turn, and so requires more of an angle from "straight ahead" than does the outboard prop/rudder to track properly.
This is accomplished with the positioning of the tie-rod between the engines on outboards and the tiller arms on rudders.
We can visualize this easily by using an example of two rudder shafts, (a rudder behind the shaft and a tiller arm in front of the shaft).
We'll eliminate "splaying/toe-in" for the purposes of clarity.
Let's say that the rudder shafts are 60" apart center-to-center, and the rudders are in straight ahead position.
Now, (while keeping the rudders straight ahead,) let's angle the tiller arms inboard so that their tie rod connections are only 56" apart, (a 56" tie rod).
With this geometry you'll see that when a steering input is given the outside rudder will turn at less of an angle relative to the inboard rudder, thereby wanting to follow a greater radius.
To get Ackerman steering in a pair of outboards, (after toe-in has been found,) the tie rod is made of such a length that it fastens to the outboards inboard of the center lines of the motors.
Edit: To condense all this down, some "toe-in" or "splaying" helps a boat to track in a straight line without "wagging its tail", and Ackerman geometry gives it better tracking in turns.