www.iFourWinns.com

The paddlewheel sensor has packed up om my 238 Vista. The paddlewheel has gone and the wire is looking sea eaten so time for a new sensor assembly. The original is a 2 wire unit plus ground. That is the easy bit. The question is which sensor is a compatible replacement for the original unit??? Ideas - experience - part number? From what I have seen on the web it looks like a Humminbird 2 wire basic speed sensor may work - but does it?

It's an Airmar unit, can't remember what model number though, i had to get one for mine a few years ago.
If you look on the four winns website and the parts catalogue it will show you:

http://parts.fwdealer.com/

On the subject of my 98 Vista 238 speed sensor, I found the solution with some help from Airmar. The correct sensor is an ST69-8 (http://www.airmar.com/uploads/brochures/st69.pdf) and it has to be fitted with a special paddlewheel, part number 20-143-1 to give the correct speed readings to the 238 VDO instrument. As at this moment the price quoted by Airmar was $86.45 for the sensor plus $15.96 for the paddlewheel. These items may not be widely available on the web so you have to call the Airmar distributor in the USA at 803-693-0777 and order them. When you speak to the technician tell them you would like the paddlewheel pre-installed and they will do that at no charge. The ST69-8 can measure speed and water temperature so for speed measurement only you use the red wire in the supplied cable to supply power for the speed sensor and the green wire as the sensor signal wire to the VDO instrument unit. The earth sleeve of the cable must also be used to ensure no signal interference to the instrument panel. Having fitted the unit I can say it all works perfectly. Airmar also suggested that their P-32 sensor will also work ok. However I had already gone with the ST69-8 so I cannot verify if this does actually work. Four Winns no longer supply the original sensor.

Thanks for the follow up, most helpful!