speedometer pick-up

[daboys]

I have a 2001 ZXO with twin 5.7 ltr merc drives. My speedometer only shows a partial speed up to 25 mph. I think the pick is clogged but can't seem to locate its position to clean. Any thoughts would be appreciated.

[Greg Maier]

It is normally next to the outdrive, mounted at the bottom of the transom. It should be a long silver pitot tube. Also check to see that the water line that runs from the tube to the speedo is not pinched. If you can't find the pitot tube, then you might have a GPS Speedo, which gets it's speed from satelites.

[Rootsy]

if those are alpha GEN II drives then the speedo pickup is that LITTLE itty bitty hole on the leading edge of the propshaft gearcase just above the bullet... which one of the two it is... i have no clue...

[GeneD]

2001's more than likely have the Gen II drives. The speedo is built into the drive.
Try taking off the hose from the gauge and blowing some air through it, not a lot, you know, just try to put a bit of pressure to it and see if you have good flow.
Could be clogged, could be leaking.

[doug hess]

I use an aero spray duster can with refrigerant propellent to blow out the pickup from under the dash. To avoid having to reach up and disconnect the line at the back of the speedometer I put in a small tee and length of hose with a plug that hangs down to a convenient spot. If it is really clogged you can watch the speed go up, yet avoid over pressuring it.

Around here it is an on going problem. In fact it stopped working yesterday as we came into the harbor. With a GPS and deptfinder/speed/water temp unit as backup there was no need to stop. I haven't gone to the next step of just leaving the can attached permanently and just giving it a blast when necessary.

[Hotspare]

And, if it's really, really, clogged ,,,,,, as in (impacted wood) like mine was at AOTH III, use a drill bit to clear the orfice before blowing .... I used a 12in long 3/32 aircraft sheet metal bit on my bravo 1 drive .... Couldn't believe all the crap it pulled out, sand, mud, wood and, whatever ...... Not sure what diameter or length bit the Alfa would require, but undersize it just a tad, as not to alter the orfice diameter ...... I only used this method as a last resort though, clearing the system with moderate air pressure was not happening ....... Ordered the bit's through a local tool store here in Dallas ,,,,, $12 Bucks each :) Good Luck ........ Bruce.