Navpilot 300 Won't Hold a Course. Please Help.

calla969

Member
I have a fairly new NavPilot 300 installation. It has a SCX-20 for the heading sensor and it's paired with a TZT3 plotter. There is also a Safe Helm 2 installed and I'm using an Octopus pump (PUMPOCT10-12). The boat is a 25' center console with a single 250 outboard using the phantom feedback.

When I first installed the system, it worked beautifully. A while ago when I was offshore it would not hold a course. It would wander all over the place and veer quite far from the track. It would start giving me alarms for being too far off course, but would not correct. I would have to disengage the autopilot and correct manually, only to have it do the same thing again once I reengaged the autopilot. I noticed today that if I put the AP in course hold, the blue line that appears on the chart plotter showing the AP course does not align with the red dashed heading line. There was no current and a light wind at my back. The two lines never come into alignment. I am using precision mode and when holding a heading, I am using the Advanced mode. I did a little research and heard that it may be due to trim tabs being deployed unevenly in a rough sea and it was having a hard time correcting. I recently did some major refitting on my boat which involved replacing the trim tab cylinders and also rebleeding the steering system. Just today, I did a test run after the work was finally complete. It was a 3 month project. Today while running the boat in the intracoastal in very calm water, I experienced the same thing. The boat wanders all over the place and once even made a pretty abrupt turn in the opposite direction of what was required to correct the direction. It seems pretty good at a fast idle speed, but on plane, it is completely useless and I would even say dangerous with that severe turn it initiated. Does anyone have any suggestions on what I should do to troubleshoot? The boat is on a trailer, so it's kind of a lot of work to test it and I have a long distance trip coming up and I was really hoping to be able to use the autopilot during that trip. I will probably only have one chance to get the boat in the water before then. If I can't get this resolved, I will not be able to use the autopilot which will be very disappointing. I would really appreciate some help. Hopefully there is a simple solution.
 
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I was just going through all of the settings in the AP to see if anything looked off. In the Sea Trial menu, there was nothing selected as the compass. I selected the SCX-20, and saved. Could that be my issue? The SCX-20 was selected in other screens and I don't get any error messages or alarms. Not sure how it would have changed.

Based on other threads I've read, here's some additional information:
Hard over to hard over is 12 seconds.
The Dockside Setup was performed with the boat on the trailer, not in the water.
Rudder Drive was set at 2. I do feel like the pump was not running enough to make corrections. Should this be increased?

The Sensors Selection menu looks as follows:
HDG - SCX-20
STW - TZT12F
SOG - SCX-20
POSN - SCX-20
 
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The rudder test and hard over timing must be done while the boat is in the water. I had a similar result when I configured the dockside on the boat on the trailer and didn't set it up while in the water. The trim tabs and other items might have started your grief but I think you should be alright if you dockside the boat in the water (min rudder test) and then seatrial the "Set Center" with the trim tabs out of the picture. The pilot sets everything up during the dockside test so that should be redone in the water. If you have an SCX20 for heading, I have no concerns there. Ensure that your speed source is setup for SOG and not STW. STW can be problematic as speed thru water sensors tend to foul. First glance, I think you will be up and running well with a bit of proper setup.
 
The rudder test and hard over timing must be done while the boat is in the water. I had a similar result when I configured the dockside on the boat on the trailer and didn't set it up while in the water. The trim tabs and other items might have started your grief but I think you should be alright if you dockside the boat in the water (min rudder test) and then seatrial the "Set Center" with the trim tabs out of the picture. The pilot sets everything up during the dockside test so that should be redone in the water. If you have an SCX20 for heading, I have no concerns there. Ensure that your speed source is setup for SOG and not STW. STW can be problematic as speed thru water sensors tend to foul. First glance, I think you will be up and running well with a bit of proper setup.
Thanks, I'll redo the Dockside setup next time I get the boat in the water. I don't have a STW sensor in the network, so whatever the AP is seeing for STW should be coming from the TZT3 which would just be GPS speed, right? Should I just set STW to none instead of the TZT3?
My Rudder Drive Level was set to 2. Should I change that setting? What is recommended, not exactly sure what it does.
How about Deviation Level? It was set at 8 and I changed it to Auto.
Also Speed Calculation. It's currently set to Auto. Is that OK?
In the Sea Trial menu, STW Adjust is at 100%. Should I change it?
Also in the Sea Trial menu, under Compass Setup there was nothing listed. I selected the SCX-20 there, but next time I turned the unit on it was blank again.
Sorry for all the questions. I'm going to be taking this trip in a few weeks and will only have one more opportunity to put the boat in the water before then if I'm lucky, so I want my best shot at getting this resolved.

Your help is MUCH appreciated!
 
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If you don't have STW, it is okay to leave it set to the TZT3 but it will never get data that doesn't exist. I normally just leave the STW selection empty when you don't have it. By the sound of it you would benefit to just factory reset it and start over. On a console boat most of the settings are AUTO or left at default. You don't setup a SAT compass like you do a Flux gate. There is nothing you need to setup on a SAT compass in regards to calibration. You only need to select it properly as your heading source. In the water the hard over time should should be between 7 to 13 seconds.
 
So I finally was able to get out this weekend and tried the autopilot after doing the reset and redoing the dockside setup. Ran straight as an arrow for 45 minutes or so, then would drift way off course and start giving me a course deviation alarm. Kept doing it all day. Would work fine for a while, then start acting crazy. I noticed the course line on the MFD didn't appear to match my actual course at some times, other times it looked correct. When I got home and was cleaning the boat, I noticed 2 of the mounting screws that hold the SCX-20 to the pole mount had vibrated completely loose and the third one was gone! The only thing holding the SCX-20 in place was the cable! Pretty sure that's going to end up being my issue. On another note, is it possible to get replacement screws for the pole mount? They appear to be custom made screws. I can't find anything similar anywhere.
 
I would be seriously worried about where you have it mounted if you are seeing that much vibration. It appears to be a standard M5 bolt thread and should be able to pick up something long enough at the hardware store. It would the lowest cost and fastest solution.
 
Thanks. Yes, it's an M5 x 25mm, but it can only be threaded on the last 10mm of the screw with the rest of the screw being thinner. It's a captive screw. The base and antenna are both threaded, so the screw needs to be able to thread through the base until it gets to the non-threaded part so the antenna will tighten against the base. I may have to get a regular screw and file some of the threads off.
It's mounted on my t-top. I think there's a very good change I forgot to tighten the screws after doing some pretty significant work. I'll monitor it, but it really shouldn't see much vibration where it is. I was out in very calm water as well. Definitely hasn't been banged around. Pretty sure it's all my fault.
 
Are you in the USA? If so and you can't find something that works let me know and I will go digging to see if I can't find something that might work for you.
 
I am in the USA. I was able to find some screws from a China supplier on Ebay that look identical except they are threaded on the entire length and have a flat and a lock washer instead of just the small flat washer. The description says they're stainless, but who knows what grade or if that's even real. I would have to file the threads off the shaft of the screws to get them to work correctly, which I can do if I have no other choice. For the time being, I'm using one of the screws that came with the SCX20 to mount it to the included mount since I'm using a pole mount. They're not long enough and I'm only getting about 1/8" of threads engaged. They're also threaded all the way, so I just pressed the antenna firmly to the base while tightening so it would seat as tightly as possible. Not ideal, but should be a temporary solution. I contacted Furuno tech support and they said the screws are not available and to see if I can find something at the hardware store. I think that unless you can find something laying around, I'll need to roll the dice on the China screws and either grind some threads off or drill the threads out of the pole mount base. Thanks for your help!
 
Ok, got out again yesterday and was really expecting everything to work after discovering the issue with the SCX-20 mount. That did not happen. The AP was entirely unusable. Worst it's ever been. It will drift off to port about 30 yards and then make a drastic correction to starboard and continue the starboard course until the deviation alert goes off and never moves back to port.

I noticed that my wheel was moving to port on its own while under way and if I trim the motor up on the trailer the motor will fall to port and I can see the wheel moving. I obviously have a bad check valve in the new helm pump. Pretty disappointing. While I deal with the warranty to get this resolved, I wanted to ask if the helm issue may also be the cause of the AP issue. I suspect so.

I have a short video of the helm behavior while manually steering using the AP, but it's too large to upload here.

If I use the AP pump to turn to the starboard stop, the wheel also moves very slowly until it hits the stop and then the wheel turns faster. When I press the button to turn back to port, the motor doesn't turn until I break it loose by manually turning the wheel. Then it moves normally to the other stop. The wheel does not turn. Then I can move back to port as normal, it doesn't stick on that stop.

After several times thinking I've found the issue, I'm reluctant to get too excited. How likely is it that the helm pump issue is also my AP issue?
 
My wheel doesn't turn at all when the AP is controlling the boat. If you can't manually steer the boat because the helm is bad, how would you expect the AP to?

BTW, are you sure it's the helm and not just air in the system and it needs to be bled?
 
The helm is brand new, so I wasn't originally suspecting it. As I said, I suspect the helm is likely my problem. The system has been thoroughly bled twice. I was going to bleed it again just to be completely positive, but I decided I'd wait to see what the helm warranty service wants me to do. I assume I'll need to send it back, so no reason to get back into bleeding again just to have to start over again when I get a new helm. Not sure how air would cause the wheel to turn. I'm pretty certain it's a faulty check valve. The wheel turns constantly very slowly to port while under way. I've never noticed this until yesterday.
Also, the AP controls the steering with an electric pump, not the helm pump. That's why I wasn't certain if it would effect the AP. I assume a bad check valve is allowing some fluid to back feed into the helm causing issues. Just thought I'd ask.

I also wonder if a bad helm could even cause the issues I'm seeing. Why would the AP steer the boat in the wrong direction until the XTE alarm starts screaming but never attempt to correct the course? Seems strange. Hopefully it's just something I don't understand and once I get the helm issue corrected I'll finally have a working AP again.
 
A bad check valve would typically result in excessive DeadBand during the rudder test. Turning the wrong direct would be the result of the dockside setup being down backwards. I would recommend completely redoing the dock side. Ensure the rudder test passes. Then check that your hard over to hard over time is 7-13 seconds.
 
I'll check it again, but I actually redid the dockside setup while I was out hoping that would help. Rudder test was good and hard over time was in spec. I'll do it again with the boat on the trailer, but it's tough for me to get it to the water to test. It doesn't appear to turn in the wrong direction, it will hold course for a few minutes until it drifts off, usually to port, then it makes a pretty drastic correction to starboard and just continues that starboard direction until alarms start going off and I manually correct. I'm really at my wit's end with this. It's getting pretty frustrating. I keep thinking I've figured it out only to get out and find that I either haven't made any difference or things are worse that they were before. I may be able to test in the water again this weekend.
 
Make sure you turn in the direction you would be turning the boat direction to. Looking at the engines will get you confused and turning the helm the wrong direction during the setup.
 
Will do. I appreciate your help and patience. I am under warranty for a few more months and definitely want to determine if it's a me problem or a hardware problem before I'm out of time. I'm still assuming/hoping it's a me problem.
 
Turning the wrong direction won't be the hardware. Direction of turn is completely determined by how you set it up.
 
It's not turning the wrong direction. It's not correcting when the boat is heading the wrong direction. The AP isn't making an attempt to correct the direction of the boat. For a few minutes it will work correctly, then the boat drifts off course, the AP makes a drastic connection in the correct direction, but continues on that course without making any further correction. It has never turned the wrong direction.
 
I worked with a customer a few years ago that went through this exact scenario.

While your autopilot pump is the piece doing the work, the only thing expected to move is the steering cylinders. When the helm moves or bypasses fluid, it is an unexpected movement. It can also be taking up the fluid that was intended for the cylinders, and the cylinders do not move, leading you to slowly drift away from course. Finally, the pilot overreacts because nothing is happening and you get the big correction followed up by what seems like no fine corrections. The NavPilot makes very fine adjustments and expects to see very fine results. It's not getting that due to the faulty check valve.

Three good ways to check hydraulic steering health:
First, you already found. Hold your hand at the top of the wheel while running straight. Does it move around the "clock" while you continue straight? That's a failure. In extreme cases you will see the helm moving on its own, like yours.
Second, turn the helm to either sides lock "hard-over". Hold pressure. Does the helm continue to move a little bit? That's a failure.
Third, you also found. The motors fall over to one side when you trim them all the way up. They should stay put.

Your diagnosis is correct and your hesitation is understandable. The steering must be correct before any further diagnosis can be done on the NavPilot. I think this is the key problem that you have been seeing symptoms of.
 
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