Re: ST4000 WARNING

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Re: ST4000 WARNING

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Re: ST4000 WARNING

Posted by - on February 06, 2003 at 05:07:00:
In Reply to: Spare Auto Pilots posted by Roger Ford (Kokomo) on February 05,
2003 at 06:14:00:


The old ST4000 has a serious, and in my opinion potentially dangerous design
flaw

In order to engage the autopilot, you flip a lever down. Once the lever is down,
the belt tightens and the autopilot steers the boat

Two issues that raise serious safety concerns are:[/i]

1) The lever can, without warning disengage itself. It usually happens to me at
the worst possible moment. I was told by the manufacturer that it needed "set
up". I took it to a repair center and had the belt tension set up. It did not
make any difference. Perhaps I just got unlucky and the repair guys didn't set
it up correctly? I have seen more than one boat with a bungee arrangement rigged
to hold the lever in the engaged position

2) SERIOUS issue. That lever rotates a cam inside the autopilot ring. When
rotated to the engaged position, the cam presses against the belt, increasing
tension on it. That tension increases the friction between the belt and ring and
that is what engages the autopilot. The lever is connected to the cam with two
little shear pins. They can break. And if they break while the autopilot is
engaged, you will be unable to disengage the autopilot. You will also be unable
to turn the wheel by hand. In other words, YOU WILL HAVE NO ABILITY TO STEER!
When this happened to me, I had been sailing under autopilot for about 2 hours,
and as I approached a very busy channel I flipped the lever up to disengage the
autopilot. Traffic was heavy and I needed to give way to other boats. I tried to
turn, and the wheel would not budge! I could not turn the wheel, no matter how
hard I tried

That's when I realized that the lever was flopping and loose feeling

I quickly re-engaged the autopilot, started the engines and pressed -10 a bunch
of times. That headed me away from traffic, back into open water

Once in open water, I motored until there was no one around. Having two engines
allowed me steerage under power

I removed the steering wheel, found an allen key, removed the autopilot ring,
and put the wheel back on. Then I headed back in again

If this had happened in more confined waters (like while coming in to a small
marina) I doubt that I would have been able to figure out what was wrong and
regain control quickly enough to avoid hitting something

Be VERY aware of the fact that those shear pins can break without warning, and
if it happens while the AP is engaged, you will NOT be able to steer! Disengage
early, and make sure that you can turn the wheel and steer before heading into
confined spaces

As an aside, Raytheon (it was still Raytheon when it happened to me) would not
offer replacement sheer pins. Their parts department tried to sell me a complete
new assembly. It was costly and stupid considering that only the sheer pins
where broken. PLUS you need a special tool to replace the whole assembly. I
bought some sheer pins locally, and I keep spares aboard for the next time they
break

Also the little wheels inside the ring break off. The replacement ring is
costly. It can be repaired by drilling a small hole through the ring from behind
and using a nut (with nylon inside to prevent it from undoing) and bolt to put
it back in place. Make sure you carry some small, long stainless bolts and nuts
to do the repair in out of the way places.
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