Inboard steering: hard to turn against prop rotation

[Lyle29464]

Re: Inboard steering: hard to turn against prop rotation

well crap! no wonder I had a hard life. I have had this wrong for 30 years.

Lyle,

I've been doing some reading to check what I suspected. A powerboat will always tend to turn better in the direction the propeller rotates due to the propeller's torque reaction. So it is as I originally deduced, my right hand prop will cause the boat to turn easy to starboard (right), and harder to port (left). Now....I need to find someone who makes wedges to correct this, or machine some myself.

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

Well we're never to old to learn right!

 

[Lyle29464]

Re: Inboard steering: hard to turn against prop rotation

Well we're never to old to learn right!

The torque turns a outboard and the stearn drive to the right. That turns the boat right. BUT we are talking inboards.

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

This phenom. is not unique to inboards, just a litlle more prominent. That is why MOST twin inboard set ups have counter rotating propellers.

You can mess with rudder tabs (similar to airplane rudder trim tabs) but it will be all trial and error.

If it really bothers you, you have a couple choices.

1. Hull trim tabs or Smart tabs will help but will not completely cancel out the torque.

2. Hydraulic steering will cancel out the torque feel. It will still be there, just not noticeable at the wheel.

I would go with #2.

BTW, the Coronado's are beautiful boats. True classics. Flat transoms and a prominent bow. I just don't like the "swoopy" stuff out there today. Especially, the "Euro" style transoms.

Thanks.....most guys my age (45) wonder why I like old boats like these.

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

My point is a worn cable will exaggerate that pressure. Turning left and right puts pressure on different sides of the cable (push versus pull). "Pushing" with a cable is much harder than pulling and will put more wear and provide more resistance.

It's not the cause of the problem but could certainly exacerbate it.

Something to check out for sure.

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

The torque turns a outboard and the stearn drive to the right. That turns the boat right. BUT we are talking inboards.

same principle with inboards with RH prop

 

[Lyle29464]

Re: Inboard steering: hard to turn against prop rotation

same principle with inboards with RH prop

Ok I give up. I agree that the torque turns the outboard MOTOR and the STERN DRIVE UNIT to the right. That turns the boat right. The same torque turns the inboard STERN to the right. That turns the boat to the left. If you have a right hand drive you can make a 360 to the left in 1/2 the distance you can make it to the right at a slow speed. If your ever in a channel about 2 or 3 feet wider than your boat is long you can turn it around turning left in 30 seconds by putting the rudder hard over left and just changing the gears a few times and give it a shot of gas. In forward the stern will jump to the right. If you try that with a right hand turn going to the right you will be a couple of minutes.

Note the above is based in your boat with a RH prop.

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

Ok I give up. I agree that the torque turns the outboard MOTOR and the STERN DRIVE UNIT to the right. That turns the boat right. The same torque turns the inboard STERN to the right. That turns the boat to the left. If you have a right hand drive you can make a 360 to the left in 1/2 the distance you can make it to the right at a slow speed. If your ever in a channel about 2 or 3 feet wider than your boat is long you can turn it around turning left in 30 seconds by putting the rudder hard over left and just changing the gears a few times and give it a shot of gas. In forward the stern will jump to the right. If you try that with a right hand turn going to the right you will be a couple of minutes.

Note the above is based in your boat with a RH prop.

I believe you're confusing the side paddle affect the prop creates with torque. Torque would tend to rotate the boat axially around the prop shaft. The shape of the prop causes it to paddle sideways. These are two different things. The reason it is easier to turn to right at cruising speed is because you are turning with the rotation thus in the same direction of the torque. When you turn left you are turning against the torque force being applied to the water by the prop.

 

[Ned L]

Re: Inboard steering: hard to turn against prop rotation

Uhm, Lyle29464 has it right. A single screw inboard with a righ hand prop (clockwise rotation in forward when viewed from the transom) will tend to turn to port in forward, and starboard in reverse (ever notice how the stern walks to port in reverse?).
Again, this is with a right hand prop. I have noticed that a good number of inboard ski-boats (mastercraft etc) have left hand props, which reverses all this.
This is one reason why power boat races are run counterclockiwse around the course (the raceboats turn left MUCH better than they turn right.)

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

My rh prop pulls my stern to port in reverse. Not because of torque. It paddles the stern in that direction.
I'm talking about what happens at cruising speed.

 

[Ned L]

Re: Inboard steering: hard to turn against prop rotation

OK, so I'm trying to follow what you are saying. I certainly undertand the torque from the engine & prop tending to cause the boat to list a bit to one side at cruising (higher) speeds. - Single screw boat, right hand prop, if 'balanced' while at idle will tend to ride a bit 'port side down' at higher speeds, - yep, got that, no issue there. What I don't get is how this causes the boat to turn to the right?
I've run a lot of boats over the years, from a 95' eastern rigged dragger, to my current Jersey speed skiff ex-raceboat, and I can't say I remember any that wanted to drift off to starboard. In fact, my speed skiff really wants to take off to the left & you really need to hold onto the wheel to keep headed straight. And to turn to the right at speeds more than 50 or so, .. you need to know what you are doing & be real careful.
The references I've found on the internet so far all have to do with outboards & inboard-outboards, but not with straight inboards. I'll do some more loking & reading, - learn something new every day you know.

 

[Lyle29464]

Re: Inboard steering: hard to turn against prop rotation

My rh prop pulls my stern to port in reverse. Not because of torque. It paddles the stern in that direction.
I'm talking about what happens at cruising speed.

now we agree. and it pulls it to starboard in forward.

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

I won't be near a computer till next week. Have to keep thisd short for now. There is actually no resultant torque unless you are accelerating or decelerating.

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

Ok.....I was wrong.....my memory is evidently terrible. Put the boat in this weekend to test new prop and drive shaft. Props too big..easy fix....vibration is gone with new shaft. However....it's hard to turn with the prop rotation at speed not the other way around as I first posted. The wheel doesn't pull wither way...it's just hard to turn to Starboard.....Sorry for the confusion.....

 

[Ned L]

Re: Inboard steering: hard to turn against prop rotation

No problem, we're all on the same page now.

 

[Guest]

Re: Inboard steering: hard to turn against prop rotation

Aren't most lower units designed with a trim tabs to counter steering difficulties? Also in reading a bit in this thread it made me realize putting a tiller stick on my 85 rude would only be hard to steer pushing towards the right and in typing this I just realized the tabs help more with tracking strait I believe. I am thinking of using a passive hydraulic steering system. If you are interested here's the link to the thread. http://forums.iboats.com/showthread.php?t=476158

 

[1980Coronado]

Re: Inboard steering: hard to turn against prop rotation

No lower unit....it's a straight inboard.

 

[mrwillya]

Re: Inboard steering: hard to turn against prop rotation

Any luck fixing this issue? I have a similar issue with my 1985 Ski Supreme.

 

[NHGuy]

Re: Inboard steering: hard to turn against prop rotation

Mark, I am enjoying this thread...we have a Century at out docks, looks to be about 21 footer & appears to be a fiberglass Coronado. It's dark blue. It used to be one of my favorite boats til I saw, horrors, a stern drive. Century runabouts need inboard drives dammit!

 

[Tahorover]

Re: Inboard steering: hard to turn against prop rotation

Mark, I am enjoying this thread...we have a Century at out docks, looks to be about 21 footer & appears to be a fiberglass Coronado. It's dark blue. It used to be one of my favorite boats til I saw, horrors, a stern drive. Century runabouts need inboard drives dammit!

I/O Coronado's are worth much less then an inboard, with a V-drive Coronado worth the most.