I have an Irwin 1978 37 center cockpit. I have seen the raymarine ST4000 for sale on ebay a number of times for a reasonable used price. I understand it is rated for a sailboat w/ a displacement of 18,000lbs. and no more than 20,000 lbs. The Mk II wheel-drive can be purchased to improve the ST4000. Then came the S1 w/ the Mk II wheel-drive which is the successor to the popular ST4000, but is rated at 16,500lbs displacement. Now the new X-5 Wheel autopilot which is also rated for 16500. Well, why did the displacement drop. If the Mk II wheel-drive can be used w/ the ST4000 then theoretically the S1 and X5 can handle the same displacement. Am I correct in my thinking or am I way off?
confused about auto pilots
- Thread starter bigsarg1
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I think you are way off. Though I don't have any of the units mentioned I can relate the data to the one I do have.
On my 37 I have a NAVICO WP 5000 which was rated for 20,000# boat, It didn't work as advertised however and when a wind puff came under sail and the boat wanted to wound up the belt would slip on the wheel drum and the boat would round up. When I spoke to NAVICO about it they suggested that i glue a belt inside out around the groove in the wheel, such that the teeth of the belt on the wheel would mesh (though not perfectly) with the long drive belt. This made a big difference but didn't completely solve the problem. Now when the boat wants to round, up the wheel doesn't slip like it previously did; instead it holds to a point where the loads cause the drive belt to stretch, and then it jumps and the boat will round up.
The point is that the loads do increase, and if you have a gear drive connection something has to give, and that most likely is going to be the gears. If they shear your autopilot is shot. I suspect that the more direct they make the connection the more they have to reduce the boat size. I also imagine that when they tried to improve the ST 4000 with the S1 w/the Mk II wheel drive, that they got a rude awakening, and had a lot of failures. Thus they had to replace it with a unit that would work with a lessor displacement.
Just my thoughts on the subject
Joe S
On my 37 I have a NAVICO WP 5000 which was rated for 20,000# boat, It didn't work as advertised however and when a wind puff came under sail and the boat wanted to wound up the belt would slip on the wheel drum and the boat would round up. When I spoke to NAVICO about it they suggested that i glue a belt inside out around the groove in the wheel, such that the teeth of the belt on the wheel would mesh (though not perfectly) with the long drive belt. This made a big difference but didn't completely solve the problem. Now when the boat wants to round, up the wheel doesn't slip like it previously did; instead it holds to a point where the loads cause the drive belt to stretch, and then it jumps and the boat will round up.
The point is that the loads do increase, and if you have a gear drive connection something has to give, and that most likely is going to be the gears. If they shear your autopilot is shot. I suspect that the more direct they make the connection the more they have to reduce the boat size. I also imagine that when they tried to improve the ST 4000 with the S1 w/the Mk II wheel drive, that they got a rude awakening, and had a lot of failures. Thus they had to replace it with a unit that would work with a lessor displacement.
Just my thoughts on the subject
Joe S
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