My speedometer has always worked fine. It is nothing fancy just the old pressure style with one rubber line going to it from the water with the pickup on the rear of the boat. I put in a new steering cable recently and was anchored in shallow water so I'm not sure which or both contributed to my speedo not working but it doesn't work anymore. I noticed I accidentally kinked the line where it goes into the back of the speedo so I thought that was it but after fixing it it still doesn't work. If I remove the line from the rear of the speedo I can blow through the line but there seems to be quite a bit of resisitance. I ran the boat in the lake with the line off the back of the speedo and no water comes out? Shouldn't it? I can't figure out what is wrong with this thing and I feel kind of dumb because its such a simple setup.

Maybe the Pitot tube on the transom is plugged? Try cleaning it out with a coat hanger or piece of wire.

Its clogged at the pick up on the drive.

If you can't blow through it i'd say it's plugged. Mine went out last year and it took me several trys to get it fixed. I cleaned the holes, checked the joints in tubes, blah blah blah. nothing. i take the guage out and hit it with super low air pressure and it works. so i decided to drain the old fluid out and refill while it was out. anyways, something musta been up with the needle cuz it worked after that.
BUT- a month or so later it stopped again! I found a slice about 1 inch long in the tube replaced and worked.
THEN- about 1 week later, it stopped again so i checked the tube and found it had exploded. literally! you could plainly see where an air pocket formed in the line and caused major stretching and expansion before the line finally gave.
SO- i replaced that just this spring, worked great for about 5 mins and the joints seperated.
TODAY- plugged them back together, re-clamped...2 mins after running they seperated again!!!!!!!!!!!! i'm gonna lose my mind soon. anyone got a suggestion for ME? lol

GPS speedo. Leaves less money for drinking, I know--but....

I hear David Richard is an expert in speedo's..you might want to give him a call...

If I remove the line from the back of the speedo it should push water out of it when I am running the boat down the lake correct? I can blow through it with my mouth but there is a lot of restriction. I should be able to blow through it freely?

freely is a bit much i think....you gotta remember, you're trying to blow air through that tiny tube all the way back to your drive. how many twists and turns does it take? more then you think, and ANY bends make it that much harder.
what have you checked so far?
and as for water coming out while running, i dunno bro. hopefully someone with more knowledge will help ya. i was just gettin this back to the front page for ya! lol