Boat pulling to starboard while underway.

Purchased a 42' CHB trawler last year. Pretty much jumped in cold to owning a boat this big and just started learning on the fly. All in all went pretty well. However, one thing I have yet to pay much attention to is the hydaulic steering system. 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.

The steering system is a hydraulic system with two helms and two rudders. I'm identifying the degrees of helm I'm giving it based on the rudder angle indicator on the auto pilot, as that is the only rudder angle indicator I have (that has functioned since I have owned the boat). Note that the problem exists regardless of whether I'm steering with auto pilot or manual. What should I be looking for in the steering system that would cause this problem? I've done a decent amount of research and have found very little information; or should I be looking at variables outside of the steering systems, boat weighting, or marine growth?

I appreciate your thoughts and comments in advance! -Ryan

Not sure but the easiest thing to check is the fluid level in the steering. Not sure if this could cause this problem but it is easy to check.

single or twin engines? Twins could affect steering if the prop rpm is not the same with the correct props.
Maybe all you need is to bleed some air out of the line. How, you will need to research or get a boat mechanic.

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

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

ryastu said:

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

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Is the boat actually turning to starboard or just the rudder indicator?
describe how you sync the engines.

The boat physically veers to starboard when the rudder angle indicator reads, '0'.

When you say, 'sync the engines', I bring them up to speed and am running them at equivalent RPMs.

ryastu said:

The boat physically veers to starboard when the rudder angle indicator reads, '0'.

When you say, 'sync the engines', I bring them up to speed and am running them at equivalent RPMs.

Click to expand...

OK, besides bleeding air from hydraulics, try this.

Get boat to speed, set up rpm as you have been doing, then add 50-100 rpm to starboard, note results and rpm.
To save time if it still veers, add another 50-100 until it tracks.
You can steer a boat with twins. The engines may not be in sync at same rpm on tach.

On mine I can track with upper tach the same rpm, I go to lower helm and they are 150~ rpm different. I first noticed this when setting both lower to same rpm, listening to engines and watching the boat veer off course.

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

Try this. Find out how many turns lock to lock, then turn it back half that amount. The rudders should now be centered. Does the boat track straight? If it does, what does the rudder indicator say? If it isn't straight then it needs adjusting.

Thank you, that's a good thought!

400, 600, 800 rpm difference I would expect it to sound awful and steer port. The auto pilot is getting a workout.
BTW, my suggestion was without auto pilot and based on your initial post that it veered starboard

Engine tachs could be way off.
Buy a laser tach from Amazon. $20.
Check engine rpm's at fan belt. Check shaft rpm's just behind trans.
Once you are sure engines are synced, move into lazarette. Make sure both rudder shafts move equally when turned manually at helm.



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On a new to you boat you can expect no accuracy in any of the systems identified in the posts above. Until you have checked them all, you can't know which one to adjust. Good luck with them all.

The autopilot can probably be recalibrated to zero, and do make sure the engines are pretty close to synched. But your description sounds like the boat physically veers, and its getting worse.

Have you checked the linkages that connect the two rudders together to make sure everything is tight? There should be a linkage bar with adjustment nuts to align the two rudders - check all fasteners and make sure the linkage points have no lateral play (there may be a little vertical play if there are bushings). Not always intuitive when boat is in water with actual rudders visible, but do the rudder shafts appear equally aligned? Any chance you can see the rudders while you stand behind the boat (swim platform)? Find a stretch where you can have someone drive the boat in a straight line while you watch how the rudders operate to assure they are working in unison.

No other symptoms such as excessive vibrations or list to one side? No recent grounding?

Peter

Greetings,
Mr. r. Agree with Mr. k. You have no idea what the source of deviation is. Might be loose fittings, wonky rudder indicator, air in steering....any number of things.


Restart from square one checking and aligning each part of your steering system. Change only ONE thing at a time then test.


You should be able to synchronize your engines by ear. Can't remember the technical terms but out of sync engines will "beat" or "thrum". Do this at cruise speed. The closer to even, the slower the "thrum". Note tach' readings accordingly.

Hi,

do twins spin in the same direction or one right-handed and one left-handed?

The single always turns litke with the rudder in the 0° position, depending on which side the propeller is on.

Nbs

North Baltic sea said:

Hi,

do twins spin in the same direction or one right-handed and one left-handed?

The single always turns litke with the rudder in the 0° position, depending on which side the propeller is on.

Nbs

Click to expand...

Twins should counter-rotate. When viewed from astern and in forward gear, the right prop should spin right, the left prop should spin left. Although there are examples of counter-rotating engines, usually the engines are the same with the reverse direction changed at the transmission. Many years ago I encountered a boat where they both spun the same direction. I could only guess that the builder or re-builder had two of the same gears on the shelf and figured "what the hell, I'll just install two of the same."

Further, on twins, the rudders are almost always offset from prop-centerline to facilitate prop-shaft removal (and almost always offset to outboard of the prop centerline).

The part that has me puzzled - and why I suspect a loose linkage - is the OP states the problem has changed and worsened.

Peter

RT Firefly said:

Greetings,
Mr. r. Agree with Mr. k. You have no idea what the source of deviation is. Might be loose fittings, wonky rudder indicator, air in steering....any number of things.


Restart from square one checking and aligning each part of your steering system. Change only ONE thing at a time then test.


You should be able to synchronize your engines by ear. Can't remember the technical terms but out of sync engines will "beat" or "thrum". Do this at cruise speed. The closer to even, the slower the "thrum". Note tach' readings accordingly.

Click to expand...

I would start at the basic stuff first. Are both rudders at the same position. Check each one of the tiller arms. Are they loose, is every thing tight? If all looks good, but out of position from each other. Than your rudders may need to be synchronized.

General speaking, there should be a valve between the two rudders. Turn the wheel all the way to Port. Open the valve and than close. You should hear a noise of the fluid moving. Than move the wheel to Starboard. Open and close the valve. Do this about 3 to 5 times.

It would not shock me that a tiller arm is loose. With time becoming looser and looser as you are describing.

The part that has me puzzled - and why I suspect a loose linkage - is the OP states the problem has changed and worsened.
Peter

Click to expand...

correct the problem has worsened over time….

mvweebles said:

Twins should counter-rotate.

Peter

Click to expand...

Correct, twins counter rotate. -Ryan

mvweebles said:

The autopilot can probably be recalibrated to zero, and do make sure the engines are pretty close to synched. But your description sounds like the boat physically veers, and its getting worse.

Have you checked the linkages that connect the two rudders together to make sure everything is tight? There should be a linkage bar with adjustment nuts to align the two rudders - check all fasteners and make sure the linkage points have no lateral play (there may be a little vertical play if there are bushings). Not always intuitive when boat is in water with actual rudders visible, but do the rudder shafts appear equally aligned? Any chance you can see the rudders while you stand behind the boat (swim platform)? Find a stretch where you can have someone drive the boat in a straight line while you watch how the rudders operate to assure they are working in unison.

No other symptoms such as excessive vibrations or list to one side? No recent grounding?

Peter

Click to expand...

I have not played with the linkages.

Probably a dumb question ( but don’t know so I’ll ask), but when you ask are the shafts equally aligned, are we talking if’s shafts that come through hull and our visible from lazarette? What indicates alignment?

I don’t believe I can see the rudders with the boat in the water. Next time I’m on-site on a sunny day I’ll take another look.

No excessive vibration or recent groundings….

Yes to all but I agree the first thing to do is verify the tachs. If they are wrong and they won't be wrong the same way then one boat side may be producing more thrust than the other. Laser pointer digital phototachs are available from Ebay and Amazon for between $20 and $30 and are accurate to +/- 2 rpm.

Of course also check that the system is not low on oil.

Do the easy things first.

I helped a fellow boater quite some years ago and his tachs varied by ~200 rpm difference total. Once he had a correction table, done at the dock, and used it to set up the engine revs he found the boat
-- ran straighter
--engines were now able to be final synched by ear. Before they were so far off synch he could not hear the rrr, rrr,rrr as they never got close enough.
--fuel economy improved
--boat actually picked up about 1/2 knot.

His tachs were the worst example I had seen of rpm variance so I remembered the problem.
He did not change the tachs but once he knew there was that level of variance he could correct for it.

To me do the above first .


Then I think I would carefully examine the rudder steering cylinder for any drift. There are two piston seals inside on the piston and if it is worn it can bleed oil from one side to the other. THe rudders will have pressure on them to move and if that seal is worn then the rudders may be able to move independent of the steering wheel. Some carefull observation with no steering wheel movement may be needed. Maybe a felt pen mark on the actual rod so any drift should show.
I don't think I would use any tapes as markers.

Or You may need to take a measurement of the piston rod extension once the boat is running straight and then again after the boat wanders. Do not adjust the steering wheel untill the second measurement is made.

That rod should not move unless the steering wheel demands it.

How do you know the boat is pulling to starboard and the helm indicator isn’t off? Are you steering a course with an auto pilot? Try aiming at a fixed point and steering by hand. Does your wake show a turn? Can you feel equal pressure on the rudders when turning port and starboard?

Any slop in the the steering linkages? As others have mentioned you’ll need to verify that both props and tachs are true? Also how old is the fluid in the helm pump and how old is the pump? Has it ever been rebuilt? Could be as simple as air in the system or as complicated as a few sticky valves. Before you begin tweaking rudders you need to rule out everything else.

ryastu said:

I have not played with the linkages.

Probably a dumb question ( but don’t know so I’ll ask), but when you ask are the shafts equally aligned, are we talking if’s shafts that come through hull and our visible from lazarette? What indicates alignment?

I don’t believe I can see the rudders with the boat in the water. Next time I’m on-site on a sunny day I’ll take another look.

No excessive vibration or recent groundings….

Click to expand...

From inside the boat you should be able to tell if the rudders are pointed in the same direction. The rudder post and the teller arm both should have a channel and block to connect them. Both rudder post on both rudders should be in the same position. If one is off, than ether one is in the wrong position.

ryastu said:

I have not played with the linkages.

Probably a dumb question ( but don’t know so I’ll ask), but when you ask are the shafts equally aligned, are we talking if’s shafts that come through hull and our visible from lazarette? What indicates alignment?

I don’t believe I can see the rudders with the boat in the water. Next time I’m on-site on a sunny day I’ll take another look.

No excessive vibration or recent groundings….

Click to expand...

I'll back-up a bit - beneath your berth in back (maybe cabinets) are the insides of your rudder posts/shafts and the linkages. Below are some generic pictures. Rudder posts usually have square tops machined into them so maybe you can get an idea if they are pointing the same direction. But check to make sure all the linkages are tight with no play. I also pulled a picture of the Hynautic system because it shows how the rudders are connected pretty well - doubtful your system has the small reservoir tank so ignore.

C-Lectric may be on to something when he suggests the hydraulic ram may be leaking past one of the seals but I think it would not be just one direction. Depends on how the ram is designed. I've included a generic diagram that may (or may not) be similar to yours. Since it would need to be removed and rebuilt (and make a mess with spilled steering fluid), I would try everything else before you do this.

When you get back to the boat, maybe some pictures of your rudder posts (beneath your aft berth?). Also, may not be relevent, but description of engines, autopilot setup so indicator is known, age of the kit and some background like that.

Perplexing to me - I'll bet someone 'cracks the code' and it's an easy fix. FIngers crossed.

Peter

In my other post, I was thinking that you may have two pistons/cylinders. That why I was mentioning syncing them. I should have made that clear.

When was the bottom last painted and cleaned ? A bad paint job could have growth growing on one side and would explain why the problem is getting worse.

I am no expert on this topic, but let me suggest that it might be fouling below the waterline with one rudder more heavily encrusted than the other. I just hauled and cleaned my boat and noticed a distinct difference in sea growth on different parts of the hull. ( My boat is single screwed. ) Is it possible that one rudder is more heavily fouled than the other and causing more drag? I am most likely way out to lunch here, but it was the first thing I thought of when reading your post.

Benthic2 said:

When was the bottom last painted and cleaned ? A bad paint job could have growth growing on one side and would explain why the problem is getting worse.

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Last summer, so maybe......