speedo readings

[mtbinscotland]

My speedos are reading quite different speeds lately (about a 10mph difference).  Any suggestions/recommendations to get them a bit more inline together would be much appreciated.

[backfoot100]

First off, make sure that the pitot pickups on the transom are clear. There's a little hole on the bottom of each one that might be partially plugged. Take a paper clip or something similar and make sure it's clear. Disconnect the hose from the top of it and then blow it out with a little compressed air. Hook the hose back up.


The speedos are adjustable. Newer ones have a small knob that can adjust the speed reading. Older ones have a small hex head screw that does the same thing. Just make sure that they're set at the speed you want with a GPS. These speedos are generally fairly accurate at the speed you actually set them at.
some people set one for say wakeboard speed and the other one at slalom speed.

[mtbinscotland]

Well, have given everything a good clean and took for a run on the weekend   still not perfect but certainly a lot better. 

Now my alternator warning light and alarm comes on when I switch on too many accessories... so another friday night on land to figure out this problem.  Could it be something as simple as a loose belt?!

[mtbinscotland]

Oh, thanks for your advice re the speedo, eddie!

[shyskier]

could just be loose, cracked, glazed belt. probably to many accessories running at one time for alternator output, or poor, dirty, corroded wire connections. ck. voltage with meter, needs to be around 13v. turn on accessories one at a time & see when voltage drops to low. ck. alt. amp output if you have ampmeter avail. Ron has said most A.S. boats have 35a alts. not enough if you add extra accessories. good chance you have voltage drop in wire connection, that would be my first guess.

[mtbinscotland]

Heading to toronto for a couple of weeks so will check it all out as recommendedwhen im back in sunny scotland
cheers..

[mtbinscotland]

Ok. Thanks for all the recommendations.  Speedos are back and seem to have just needed a bit of a cleanout.
cheers!

[RonT]

If you have the original black airguide pitot pickups they are known for clogging easily. The new style has a small plastic "guide" that shed debris away from the small opening. If you continue to have problems you may want to replace the pick-ups.
Part # ASH-0080-OP

[mtbinscotland]

Thanks. I'll keep my eye on them.