Boat pulling to starboard while underway.

[ryastu]

I really appreciate the information, and time you folks put into providing it! You guys are awesome! I'm in a way better spot then I was 24-hours ago.

 

[fgarriso]

As we talk through this, I should have mentioned I did try this back in February, my log notes are below. One thing I have not done is looked at the upper and lower helms to verify consistent RPM readings.

○ Messing with engine RPM to see how it effects rudder angle while running on auto pilot:

@2400 port and Star at 2800, it still steers to the port, seems to bounce between 2 and 5 degrees to steer a straight course

@2200 port and Star at 2800 ,it still steers to the port, seems to bounce between 1 and 4 degrees to steer a straight course

@2000 port and Star at 2800, it still steers to the port, seems to bounce between 0 and 3 degrees to steer a straight course

If I am reading this correctly you are reducing engine speed on the port engine and steering to PORT.
Have you tried reducing the starboard engine?
Does the helm wheel pull to one side or the other?
Have you tried picking out a fixed landmark and steering to it?
Don't watch on your rudder angle indicator to do the test.

 

[Kapn]

Rudder angle indicators are usually based on electrical resistance. Everyone here has covered the mechanical issues of checking the rudder, bottom condition, engine rpm, etc. Corrosion on the wire connection is most likely the cause of a rudder angle indicator showing incorrectly. I've also seen them damaged if something has pressed against it like in a crowded laz where gear falls or gets pressed against the indicator. Some are better built and protected than others, results may vary.

 

[ofer]

lots of good information in this thread...BUT would you know you have a problem without a rudder indicator? if the answer is no, just calibrate while on the way with what you think zero is. sorry i always start with simple first.

 

[backinblue]

lots of good information in this thread...BUT would you know you have a problem without a rudder indicator? if the answer is no, just calibrate while on the way with what you think zero is. sorry i always start with simple first.

I agree and was about to say the same. You may think it's "pulling" to one side just because your rudder indicator says 5 degrees while going in a striaght line. My boat had the same issue until I made a slight adjustment of the angle sensor and now it's 0 degrees while going straight. I have a single prop and rudder so less variables than you but make sure you are not trying to fix something that's not broken. If you actually feel like you have to steer to one side in order to maintain a straight line, then look into many of the possible reasons pointed out so far.

 

[rgano]

Maybe the rudder angle indicator is off. Check the linkage in the lazarette.
Regards,
Scott

Took the type right out of my fingers, as did backinblue....

 

[Tator]

As we talk through this, I should have mentioned I did try this back in February, my log notes are below. One thing I have not done is looked at the upper and lower helms to verify consistent RPM readings.

○ Messing with engine RPM to see how it effects rudder angle while running on auto pilot:

@2400 port and Star at 2800, it still steers to the port, seems to bounce between 2 and 5 degrees to steer a straight course

@2200 port and Star at 2800 ,it still steers to the port, seems to bounce between 1 and 4 degrees to steer a straight course

@2000 port and Star at 2800, it still steers to the port, seems to bounce between 0 and 3 degrees to steer a straight course

Early morning and an old man brain trying to figure this one-so forgive. To me, the figures you give are showing the opposite reaction to what I would expect. That is, I would think that as the port the engine rpms decrease in relation to the stbd engine the angle needed to compensate should increase not decrease.

Tator

 

[SteveK]

In post #1 the OP said veer to SB and verified by rudder indicator. I immediately took veer as physical steering, not a rudder indicator showing differently while going straight.
I suggested to turn off autopilot to eliminate that input and slowly add rpm to SB without Auto and see if it will hold a course with manual adjustment. With twins you can steer a boat.

The tachs are possibly off. While a photo tach will tell you engine rpm it does not tell you prop rpm. What if the props are not tuned to travel the same distance through water. Both engines turn the same way but one trans will run reverse spin.

 

[porman]

rudder indicator

lots of good information in this thread...BUT would you know you have a problem without a rudder indicator? if the answer is no, just calibrate while on the way with what you think zero is. sorry i always start with simple first.

Exactly. see post 10.

 

[mvweebles]

See post #1. My read is OP describes a mechanical issue, not a sensor issue.

. I noticed last summer that it would pull slightly to starboard (1 to 2 degrees) so in order to maintain a straight course i would need to give it 1 to to 2 degrees of rudder to port, as summer gave way to fall, I noticed by November the pull had increased to 3 to 4 degrees, and by February it appeared to have increased again to 6-7 degrees.

Peter

 

[ryastu]

lots of good information in this thread...BUT would you know you have a problem without a rudder indicator? if the answer is no, just calibrate while on the way with what you think zero is. sorry i always start with simple first.

….I probably would not know. I do feel like the steering is a little sloppy, which posters have detailed more than a few reasons that could cause this; I have not touched power steering oil in the year I’ve owned the boat, which will definitely change next time I step on the boat…

 

[backinblue]

See post #1. My read is OP describes a mechanical issue, not a sensor issue.

. I noticed last summer that it would pull slightly to starboard (1 to 2 degrees) so in order to maintain a straight course i would need to give it 1 to to 2 degrees of rudder to port, as summer gave way to fall, I noticed by November the pull had increased to 3 to 4 degrees, and by February it appeared to have increased again to 6-7 degrees.

Peter

Guess it depends on how you read it. To me it sounds like he needed to add a couple degrees to port (per the rudder angle indicator) in order to keep it straight. If he put the rudders at zero (again per the a/p display) the boat would veer slightly to starboard. It could be a mechanical issue or simply that the zero position is slightly off and needs adusting/calibrating.

 

[Brooksie]

The top of your rudder is always more effective than the bottom. B/c it has an end plate or dam on top, the hull. So depending on your propeller direction of rotation this will create an imbalance in steering force required. Several means exist to make either the top less effective or the bottom more effective.

 

[Hippocampus]

Point about growth has some merit (although don’t think it would produce that much pull to one side). Many boats are always docked with the same side facing the sun or the same side facing the prevailing current. Then growth can be quite asymmetrical.

 

[DennisB1]

Lots of good suggestions on making sure your rudder linkage is tight. Check to see if the rudders track and repeat when you go to stop to stop using the helm. The rudder angle sensor connects to the rudder arm or tie rod and is independent of the hydraulic ram. It should be tight with no free play. I would have a diver do check to if the blade moves relative to the shaft. There should be no movement. Then have him clean the props, rudders, shafts and bottom. One side of my boat got more sun and growth than the other side causing more drag which affected rudder angle underway. Which was solved by a diver cleaning.

 

[RickyD]

If it is gradually worsening then my experience will not help. I have a new digital indicator as part of my new autopilot which is right on. I have an old analog unit that was off. I just bent the arm a little till it was really close. So I use it when I have not turned on the Autopilot.

 

[Don L]

I noticed last summer that it would pull slightly to starboard (1 to 2 degrees) so in order to maintain a straight course i would need to give it 1 to to 2 degrees of rudder to port, as summer gave way to fall, I noticed by November the pull had increased to 3 to 4 degrees, and by February it appeared to have increased again to 6-7 degrees.

Since it has been changing, what have been the tank levels during all this?

BTW - I have a trawler friends who had same issue and it was a bent rudder. But I wouldn't expect that to change by itself.

 

[RT Firefly]

 

[fgarriso]

 

[Bkay]

I haven't read all the comments, just a few and all is good advice. Hope this isn't rehashing another response. To me, the first step would be to look at the rudder arms from inside the boat and see if the rudders are aligned and both turn stop to stop.

I had a similar problem and I ultimately found the rudders were not aligned. They were slightly toe out (trailing edge closer than leading edge). With the RAI on only one rudder arm, it told me I was pulling in one direction - in reality I was splitting the difference between two misaligned rudders. In my case, I simply had to adjust the tie rod (I have a liquid tie bar, but adjusting a mechanical tie rod is even easier). I went with a very minor toe-in (a degree or so). I also picked up a knot at WOT with this.

I guess I should mention that I actually lived with it for a bit until I hauled the boat because I wanted to physically look at the rudder to confirm the rudder arm was in exactly the right position for both rudders.

After adjusting rudders, I re-calibrated my autopilot RAI following the manufacture instructions. Easy peasy.

 

[ryastu]

Correct, if the rudder angle indicator is at 0, the boat steers to starboard…

 

[O C Diver]

Couple of things to check:

If you disconnect the hydraulic piston rod from the rudders, you can check for play in the various components. If the piston rod moves in the cylinder, or with someone else turning the helm wheel back and forth one full turn and there is noticeable play, you have air in the system. The two rudders should be tightly linked together. If a friend holds one and you can move the other, you have play and probably worn parts in the system. Everything from the hydraulic cylinder to the rudders needs to be tightly linked without play.

Most rudder angle indicators have a linkage that pivots on ball joints. Gently grasp the connecting rod and move it back and forth to check for play. Try to to turn the connecting rod. While it may turn about a quarter revolution, if it can turn several revolution, this could be one of the problems introducing error into the system.
Disconnect one end and check for smooth movement of the arm in the rudder angle sensor.

Ted

 

[DrissZougari]

The first thing to do with twin engines is to confirm that your tachs are reading the correct RPM. Since the issue is worst means that your tach pick up may be loose due to engine vibration.
good luck,

 

[Circumnavigator]

Mentioned above: Check rudder angle indicator -- either haul the boat or get a diver to help you set the rudders to actual zero and then see what the indicator reads.


Not mentioned above: Check fluid in both transmissions. Buy handheld tach and check to see that shafts are spinning at same speed -- one trans might be slipping. Check that difference between engine RPM and shaft RPM is in fact the trans ratio. (Engine RPM=Shaft RPM x ratio)


Jim



It's possible that the props don't have the same pitch -- weird things happen -- but that doesn't account for it changing.

 

[Nepidae]

Pulling to stbd

After you have tried all of the suggestions call the manufacturer of your autopilot/MFD.

The autopilot could be trying to take you someplace it thinks that you want to go.

New boat to you, you don't know what the PO did or didn't do.

I'd start with a system updates to firmware and charts.

Then, if it was a Garmin I'd suggest doing a dockside setup to make sure that the MFD & Autopilot were working together.

Garmin has great support for their products and you can reach them at 800-800-1020.

Good luck.

 

[Capt Q]

Bucket

Similar problem, turned out a 5 gallon bucket was in the steering,, it would get smushed when auto pilot was on and spring back with Auto off and drift to Port with a mind of it’s own..
was not immediately obvious,, innocent bucket sitting/stored in the lazarette..

 

[Owen Christensen]

I wouldn’t trust the tachs.

 

[DW1979OA]

I got the impression that the OP thinks it is pulling because that is what the rudder indicator says. My rudder indicator has a recalibration button. Could be as simple as that

 

[Californian38]

Yeah, it is a twin engine.....

Put the rudder indicator at zero. Jump in the water and visually look at both rudders. May be a loose component. Did you get a out of the water survay done?

 

[Californian38]

Good one!