[TG] [TG11] Autohelm T300 computer & Raymarine Smart Heading Sensor via NMEA

[Tom - Raymarine - Moderator]

Hello Sergio,

The T1 Linear / EV200 would be right at the upper limit of its specification. So that you can make an informed decision, here are the potential problems you might encounter when using a pilot that's right on its upper specified displacement limit, for blue-water cruising.

1. Greatly accelerated drive wear and likelihood of early failure. If you use a small car to tow a large boat a short distance to the boat ramp occasionally, no problem. If you use the same car to tow the boat across the country, it probably won't get to the end of the journey.
2. Higher likelihood of failure of the drive FETs in the Actuator Controller (ACU). The FETs in the ACU200 are lower-rated than those in the ACU400 and if they're running at close to the specified maximum current for long periods then they'll get very hot and be much more likely to fail. This would leave you with no drive output (no functional pilot.)
3. The drive may stall when you need it most, e.g. when the pilot's trying to prevent a gybe in a following sea. Keeping the sails well balanced helps keep the pilot's load down much of the time, but makes little or no difference when it's a sea that's pushing the stern round and the pilot is trying to force the rudder back the other way. You might not feel all that load at the helm but you have a large mechanical advantage there compared to the drive (its stroke is 300mm whereas your wheel's movement is say 3 turns of perhaps 3.5m circumference to achieve the same rudder movement.) Several decades of experience of building pilots has taught us that vessel displacement is the best guide to the maximum loads that the pilot's likely to have to cope with under such circumstances.
4. The Actuator Controller (ACU) may reach its peak current and raise a Current Limit alarm, causing the pilot to drop to Standby. Again, this is most likely at times when you least want it to happen.
   
   

The key differences between harbour usage and ocean passage-making are the very high duty-cycle, the fact that you're out in all weathers, and the consequences if the pilot can't cope. I don't like taking support calls from people who've had to hand-steer watch-and-watch for 2 weeks, so I always recommend over-specifying the pilot, and if two-up or solo, having a complete second pilot installed with an On-Off-On changeover switch (not just sitting in a box ready to be fitted at sea.) In your case, I'd keep the T300 as the backup and install an Evo as the new primary.

We don't expect a well-specified/installed pilot to fail, but it's possible - what happens if it does, is the question I ask people.

Regards,
Tom