Pontoon Boat & Deck Boat Forum

Called the svc dept and they said the intake was on the skeg, just above the bullet. It's a new Merc 150 4stroke. Any suggestions? Tried a small drill bit on the only hole I could find in front of the cooling intake holes....Help!

So your speed pick up is part of your engine, I had a seprate pick up on my right pontoon, I'm not putting it back with the rebuild, GPS will tell me the speed if I care

There's a little hole at the front (sharp end) of the lower unit. It attaches to a rubber tube (called a pitot) that goes up to your speedo. The speedo reads air pressure as the water pushes into the hole. The faster you go, the more pressure, the faster your speedo reads.

If the speedo doesn't work, there's a few things that could go wrong.

1. The hole is clogged
2. The tube came off from the connection to the power head from the lower unit
3. The tube is split or cut somewhere between the engine and the speedo
4. The tube came off the back of the speedo.

#4 is pretty common, and usually the easiest to check. It's also the easiest way to troubleshoot the other problems.

Pull the tube off the back of the speedo and blow (or use LOW PRESSURE - 5 PSI or less) into the tube. Have someone check the hole on the lower unit to see if air is coming out, or use soapy water and look for bubbles.

Sometimes that's all you need to clear the line if it's clogged with sand or silt. If there's no air coming out of the hole, then it's probably #s 2 or 3.

I've got an Optimax on my bass boat and I quit worrying about the speedo a long time ago. I think it takes about a 1/32nd bit to clear out the hole and here at Lake of the Ozarks there's a lot of crap in the water in the spring. I just use the tach.

If you have a smart phone there are many apps that can tell you your speed. The one I used is much more accurate than any pitot based speedo. It's called "Ulysse Speedometer".

When people ask if I have a smart phone, I tell them it is mildly retarded.

RonKMiller wrote:If you have a smart phone there are many apps that can tell you your speed. The one I used is much more accurate than any pitot based speedo. It's called "Ulysse Speedometer".

yep it is awesome!!!

Many thanks for the tips and directions. It was so crammed with dead wood that I had to start with a 1/16 th bit and move up from there. Bit I had yesterday was too big to fit the hole, which was so small I just thought it was a knick in the skeg. More to ease my mind that the new boat wasn't broken. Will use the Fishfinder for speed from now on. Thanks also for the smart phone app. Very cool!

no prob I use it in the car too, to keep an I on the admiral's speed....

most folks will agree that pitot speedos are pretty unreliable. even when mine is clean an functioning on my honda (same location as yours), it pretty inaccurate until i get to around 10-15mph. the only reason i ever clean it out is my ocd kicks in when i see a gauge not working. otherwise i use the gps i have mounted to the helm for speed.

I'm really glad I don't have a pitot speedo. The GPS is all I have.

Got the speedo app loaded and used it running around town working, the HUD works good, just lay it on your dash and read it on the windshield