Fix or upgrade autohelm St4000+

[Jfloyd85]

I’ve been fixing up a 1985 Pearson 28-2. It currently has an autohelm st4000+ which works, but not well. I’m guessing it is around the 2000 vintage maybe older. The screen is sun damaged and basically worthless, but push auto and she works under motor or light air. However under sail eventually it starts to over correct, the heavier and gusty the wind, the faster it becomes worthless. I can usually lock the wheel and do a better job just adjusting the sails. I’m guessing I could adjust some of the wander out if the screen were legible and I could adjust its settings. Also I’ve read a ruder position sensor would help.

I did recently take the drive unit apart and replace the belt, clean and lube. It’s in excellent condition for its age. The new raymarine evolution 100 can be had for a little north of $1300 this is not something I can do right now. Currently I don’t even have a gps chart plotter. I don’t need one for day sails, which is 95% of my usage, but I’d like to start doing overnights and weekend trips into more unfamiliar waters. expanding the sail inventory is also a little higher on the importance than 1300 for a new AP. I’d like a drifter for the lighter days and a 100% jib for the heavy ones.

Back to the AP... I really need one if I’m going to do any cruising as I’m single hand more than 50% of the time. So will I see a huge improvement with the evolution over a normally functioning st4000+? I’m estimating I could piece together an upgrade for $300-500 utilizing older fluxgate era components. Maybe a smartpilot computer and 5000 or 6000 display and adding a rudder sensor (could be reused if I upgrade later) I’m leaning this way if it will buy me a few years on a total system replacement, but don’t want to throw money at something with little return on investment (performance.)

Thanks for reading!

[Frankly]

You might want to consider a rudder reference unit as your first move. In my experience with the RM autopilots 4000, S series, X series, and now Evo, none work to their potential without a rudder reference. You gonna need one sooner or later so just a good place to start.

The autopilots with heading rate sensors are a significant step forward. If you stop and think about it the rudder does not control the ships heading but the rate of change of the ships heading. There is an integration process that goes on either in the helmsman mind or via the fluxgate. In an ideal world if you steered your ship to the correct heading, engaged the rate only autopilot and it did a perfect job of maintaining the heading rate at zero (as the wind and seas tossed the ship around) then the ship would always remain on the desired heading. Real world don't work that way so we have to include a heading sensor (fluxgate) but the real important parameter is rate. Used to take expensive and large gyros, now size of a pea and cost dollars.

You may find the rudder reference is all you need to get things under control. Seeing all that info is nice but not essential. IMO the X-5/ 6000 display is the best of the bunch until the EVO came along.


Frankly

[Marathon1150]

I am facing a similar dilemma. We have two boats, one with a Raymarine SPX5 wheelpilot and also a Raymarine 2000plus tillerpilot that attach to a tiller extension on a Hydrovane windvane, both used only when we are motoring. The SPX5 is ok but is sometimes overwhelmed and loses the plot. Fortunately it makes a lot of beeping noises when that happens so we can manually intervene and get everything back on track. We don't have a rudder sensor. Everything works well enough however that I do nor intend any upgrades or swaps. When sailing we normally use the Hydrovane and it works very well.

I installed the wheelpilot in 2009 and since then we have had to have the course computer repaired and the wheel assembly replaced. The original disintegrated into a shower of ball bearings and fractured plastic. We also bought a reconditioned course computer because we were heading offshore and redundancy of spares is a good idea.

However we have a second boat with a Navico (now Simrad) WP5000 autopilot on the wheel. It also has a "windvane" that is intended to help the autopilot when sailing. This system is probably probably from around 1990 or so and it suffers from intermittent failures. Sometimes it will steer reasonably well and sometimes it will go seriously off course. We have not used it very often because of its unreliability so I am planning to do some on the water diagnostics soon.

In the meantime I am also considering swapping out the Navico for a new model Raymarine such as you describe. The cost is a bit of a barrier however, hence the planned diagnostics.

I look forward to hearing further opinions regarding your original question.

[Jfloyd85]

I’ve ordered the rudder sensor, used ones can be had for around $100 but I went for a new open box at 150. I’ll update when I get it installed

[Frankly]

The RM unit is basically a spring loaded potentiometer with an operating arm. The spring loading is not high, but removes play or backlash from the rudder position measurement. A short length of aluminum flat bar and a couple of SS band clamps should do it. Most straight forward arrangement is to make the center to center distances same for rudder shaft and position sensor. Just be sure to arrange installation so that the real rudder stops stop the rudder not the sensor or you will be looking for a replacement.


Good luck, hope this gets you where you want to go. Like I said the display end is nice but not necessary assuming you can read enough to get through the calibration part.


Frankly

[goboatingnow]

The ST4000+ isn't a bad AP, it was often married to a wheel pilot which tended to be crap, however coupled to a linear drive , its not a bad pilot

[Jfloyd85]

Well, I scored deal on a complete Evo kit that I just couldn’t pass up. $950 new open box. I’ll be listing the old st4000 components on eBay if anyone is interested. I’ll definitely be updating the thread with my before and after impressions. Also going to install the rudder sensor. I was hoping it would have come yesterday so I could try it out on the old system. Probably won’t see it until early next week and the new AP will be here mid week.

[Pete7]

This thread might be of interest to you.

https://www.cruisersforum.com/forums...ew-136885.html

Did the new Evo 100 kit come with a wheel drive? think carefully about whether you want to use the old black one with brass gears or the new grey one with plastic gears. I kind of regret selling my black wheel drive, but it fetched good money and helped pay for the Evo 100.

Pete

[Jfloyd85]

Thanks for the link. Yes, a complete kit with new wheel drive unit. I’ve taken apart the old one, it has a few brass gears but it’s also mostly plastic. I was considering, keeping my black old drive unit and selling the new one as I could likely recoup half what I paid for the kit. The old drive unit is in very good condition and I could run it until it craps out and then go for a linear drive.

[Jfloyd85]

Got the install done on the new AP. Wow, night and day difference, and I have not yet installed the rudder sensor. It made it several states in the care of the USPS and was evidently lost about 2 hours from here. My heading sensor is mounted nearly around the waterline and center of the keel as well as close to the centerline of the boat as physically practical. I took apart the old drive unit and serviced and lubricated it. The way the new pilot commands the voltage it’s nearly silent. Conditions were pretty light today but I can already tell a huge difference. My boat is 28’ and 7000lbs dry with a large rudder and regular fin keel, 5’ draft