Speedo Quit

[Sasquatch]

My speedometer has quit working again. This has happened several times. The first time I thought it was because I stopped too quick and rammed water back up the pitot tubes. I blew them out and whala it started working again. Welll it happened again and this time moisture was in the guages. I took the unit out, dried it out and resealed it with silicone (clear RTV). The speedo started working again...whew. Again the speedo quit. This time I was sure not to stop too fast but it stopped anyway. Well this time I found mud in one of the pitot tubes...we have lots of problems with mud dobber wasps in our area... found more water which I blew out but alas no speedo workie.

What gives???

SAS

Edited June 30, 2006 by Sasquatch

[SacRiverRat]

Dang... another misleading topic

... to be helpful... have you tried removing the two speedo hoses where they go into the gauges, and allowing the water to blow through? Might find that they are stuck up with something

[Sasquatch]

Dang... another misleading topic

... to be helpful... have you tried removing the two speedo hoses where they go into the gauges, and allowing the water to blow through? Might find that they are stuck up with something

Sorry for misleading you...I'll never wear one of those damn things!! Might scare the population.

Yup..I took them both off from the gozinta of the instrument cluster and blew back thru the tube to drip out of the pitot tubes. Man are they long and take all my lung force to blow them out!! My head was a poundin and I think I might have blown out one of my eyeballs. I'm sure they were clear of water but still no workie.

I also took a .030" wire and made sure nothing was blocking the thru tubes of the pitots. The leading edge tube where the water first goes in the the tube was where the mud dobbers like to pack it in. Q-Tips and water work well to get the mud out. Now I leave a Q-Tip in while the boats in the driveway. I put a flag on it so I don't forget to remove it before launching. Makes me check my butt plug too. Not to be misled.

SAS

[jayjoans]

Man, I don't even want to know.

[John I.]

Sorry for misleading you...I'll never wear one of those damn things!! Might scare the population.

Yup..I took them both off from the gozinta of the instrument cluster and blew back thru the tube to drip out of the pitot tubes. Man are they long and take all my lung force to blow them out!! My head was a poundin and I think I might have blown out one of my eyeballs. I'm sure they were clear of water but still no workie.

I also took a .030" wire and made sure nothing was blocking the thru tubes of the pitots. The leading edge tube where the water first goes in the the tube was where the mud dobbers like to pack it in. Q-Tips and water work well to get the mud out. Now I leave a Q-Tip in while the boats in the driveway. I put a flag on it so I don't forget to remove it before launching. Makes me check my butt plug too. Not to be misled.

SAS

I'm not sure what multiplying has to do with your speedometer. (from the Jethro Bodine school of mathematical studies: 2 gozinto 4 two times, 2 gozinto 6 three times...)

Are you sure the speedo's prior failures were actually due to the causes you stated? Mine would sometimes not work after I had killed the engine to pick up a skier/rider, but then would work again 2 or 3 re-starts later. Sometimes it would not work again until the following day. Eventual dealer solution was to replace the speedo. It worked.

[Lakenut]

Mine will do the same thing sometimes. After I stop and turn the key off and then start back up it works again. It only happens about once every 20 hours or so, so no big deal. Another reason to have a GPS on board.

[Malibudude]

Don't have any issues w/ mine not working after I cleaned them out. Is it possible to damage the pitots while removing crap frm inside them?

[Sasquatch]

Don't have any issues w/ mine not working after I cleaned them out. Is it possible to damage the pitots while removing crap frm inside them?

I suppose that is possible. I think the principal used is Bernoulli's law...a fluid passing faster past a fixed point (venturi tube) than the rest results in a lower pressure and so if the orifice is changed the pressure drop may be changed as well. Anyway...I don't think I changed the orifice by running a wire thru it but maybe...I had done this before an the speedometer worked just fine. I've cleaned them again with q-tips and blew them out one more time and if that doesn't work I may go into the instrument cluster again looking for water, bugs or some other evil demon.

I don't know why Malibu used this system for sensing speed. Maybe thats why they went to the paddle wheel...which after reading some of those posts doesn't seem to be an ideal speed sensor either.

SAS

[WakeGirl]

Don't have any issues w/ mine not working after I cleaned them out. Is it possible to damage the pitots while removing crap frm inside them?

I suppose that is possible. I think the principal used is Bernoulli's law...a fluid passing faster past a fixed point (venturi tube) than the rest results in a lower pressure and so if the orifice is changed the pressure drop may be changed as well. Anyway...I don't think I changed the orifice by running a wire thru it but maybe...I had done this before an the speedometer worked just fine. I've cleaned them again with q-tips and blew them out one more time and if that doesn't work I may go into the instrument cluster again looking for water, bugs or some other evil demon.

I don't know why Malibu used this system for sensing speed. Maybe thats why they went to the paddle wheel...which after reading some of those posts doesn't seem to be an ideal speed sensor either.

SAS

Bingo. While the paddlewheel isn't ideal, it's worlds better than the pitots. Most ski boat manufacturers used them at one point or another, & I'm sure that there are some out there that still are. But yeah, it's a system that is prone to problems because of clogging.

[mrothwell]

Don't have any issues w/ mine not working after I cleaned them out. Is it possible to damage the pitots while removing crap frm inside them?

I suppose that is possible. I think the principal used is Bernoulli's law...a fluid passing faster past a fixed point (venturi tube) than the rest results in a lower pressure and so if the orifice is changed the pressure drop may be changed as well. Anyway...I don't think I changed the orifice by running a wire thru it but maybe...I had done this before an the speedometer worked just fine. I've cleaned them again with q-tips and blew them out one more time and if that doesn't work I may go into the instrument cluster again looking for water, bugs or some other evil demon.

I don't know why Malibu used this system for sensing speed. Maybe thats why they went to the paddle wheel...which after reading some of those posts doesn't seem to be an ideal speed sensor either.

SAS

The venturi got clogged much less than the standard pitot. I had one of each on my Echelon. I think Malibu used them because it was better then the old style.

[RTS]

While the "venturi" pitots Malibu uses look like they would operate by the aforemention Bernoulli's principle, in fact they do not. The pitot functions by water pressure building up on the face of the larger hole and sending pressure up to the speedo. Turn your key on, cover either the front or rear hole on the pitot and blow into it...you'll see your speedo register. Sucking doesn't work. If they were using Bernoulli's principle, you'd have a vaccum where the "holes" inside the pitot intersect..

When I first saw the design, I though the same as you until I had to work to clear some debris and did some experimenting. The "venturi" design I think is more so very small debris (silt, maybe some sand)can pass through the pickup, rather than be forced up the tube and create a clog. But the difference in the size of the hole in front and rear allows pressure to build and run up the tube to the speedo.

I find that a paper clip works well for clearing them out...

[UWSkier]

rts is right. The Malibu system is a positive pressure system versus a negative pressure system like is used in most other boats.

Good riddance to all those systems!

[ibelieve]

I use to keep a basketball pump on board, with a small hose attached that would fit the back of the pickup. I would then pull the hose off the pick, attach the one from the pump, and blow it out. Sometimes it was all I could do to get the pump fully depressed before the pickup would clear.

I could do this from the platform by reaching under it and disconnecting/connecting the hose to the pickup.

Once in a while something would get dried out and harden in the pickup and I would have to use a needle or safety pin to clean it out.

/Steve