I just bought a 1996 Maxum 1900 SR which the speedometer does not operate on. Does anyone know what to hceck on this? I can't imagine the circuit is very complicated but trying to make out the wiring diagram on the pdf manual is impossible :-(.
check the little pin hole size hole on the front lower part of the outdrive, stick a small drill bit in there to clear the hole. Also check the speedo tube that its attached I believe its by the shift foot on the outdrive
Assuming that you have an Alph I/O, there is a VERY LITTLE hole on the leading edge of the drive. You might not even see it if you don’t look closely, but you can certainly feel it if you run your finger along the front edge. It’s above the “bullet”, but below the cavitation plate.
Anyway, it’s a little “V” shaped hole in the front edge. Take a small drill bit or wire and push it in the hole. If you insert the bit and it goes in about 3” and hits metal, you don’t have a clog. If it doesn’t go in 3” or you don’t hit metal, turn the bit BY HAND (don’t use a drill), and it will grab the clog. Pull the bit out, remove the debris from the bit, and do it again, until you get the bit to insert all the way and hit metal. Then you are unclogged.
If you remove the clog (or didn’t have one to begin with) and your speedo still doesn’t work, look above the front of the cavitation plate. There is a plastic connector. Take it loose by turning it (counter-clockwise, I believe), then blow thru the hole on the leading edge. You should be able to blow through. I did it with my own air, no problem.
If you don’t have a clog in the hole and are able to blow through, then you either have a clog in the line you just disconnected, or the speedo diaphragm is broken. The next step would be to disconnect the tube from the back of the speedo and blow back toward the drive, with the hose still disconnected at the drive. Don’t blow towards the speedo with the tube connected, or you will rupture the speedo diaphragm.
All the above is correct. One additional trick, I actually put my mouth over the small hole after poking around with the small drill bit and applied a small amount of pressure. My son was watching the Speedo at the time and reported, "there it goes dad". A tick later a small clump of mud poured out the opening, and from then on it has worked perfectly. The key here is that it is a pressure measuring device.