Re: Speedo Question
Originally posted by cuzner:<br /> Hey Greg....they measure the vacum created , you would have to "suck" the air out of the tube to get it to register anything. <br /> Jim
I believe this is incorrect. Most, if not all, are air pressure guages as DJ said, not vaccuum, unless it's paddlewheel type (yours is not paddlewheel). This has been discussed many times on this forum, do a search on "speedometer" and you'll see a bunch pop up. Very true that most failures are caused by gunk, slime, wood mulch, or hard water deposits clogging the pickup tube. Usually cleaning the tube cures the problem. In your case, it sounds like you're simply missing the entire pitot pickup that DJ posted for you. If you want to test your speedo right now, you can just apply a little compressed air into the end of your bare tube while looking at the needle...oh wait...you aready did that and the needle jumped under air pressure, right? So the gauge is likely fine. So just buy that little plastic arm and mount it down low on your transom, hook your tube to it (or replace the tube if it looks old & cracked), and your speedo will be fixed. OR....depending on your motor, many motors have a speedo pickup tube built directly into the lower unit. See if there's a place hidden down there to hook up that pipe you found, it might simply be disconnected and needs to be hooked back up. Often you'll find a small hole in the leading edge of your lower unit...this is a built-in pitot tube and you won't need to buy a thing after you clean this tube out and hook up the pipe. I don't know about your old machine, but most newer boats have the built-in type and the plastic arm on the transom is becoming rare. <br /><br />By the way, whenever I have a question that's not too obscure, I usually type it into Google. For instance, "How does a boat speedometer work?" "How many feet are in a Kilometer?" "Why does my ying-yang hurt?" Make sure you put the question mark in and Google is a pretty smart search engine, often just pops the answer right on your screen in big print. It worked well for me on all of above except for the last one.
Google is an extremely powerful research tool once you learn some of the little tricks beyond the cryptic key-word searches that most of us use, which often result in too many unrelated answers. Good luck on your resto!
