Mine does this all the time.
I just keep cruising and the readings come back to actual speed
There has to be a better system
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| Jammed speedometer pickup tube? https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=932 |
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| Author: | pet575 [ Tue May 29, 2007 8:13 pm ] |
| Post subject: | Jammed speedometer pickup tube? |
In my first weekend with my new 220 Horizon, I managed to run through some junk in the water. Not sure why/how, but for some reason my speedometer stuck at 38MPH, stuck at 34MPH for awhile, and is now stuck at 30MPH. It does not move at all. My theory is that whatever junk I was running through somehow clogged the speedo's pickup tube on the lower unit, thus holding the water pressure in there and making the speedo think it is at 30MPH. The gradually declining speed it is stuck at makes me think that just a bit of pressure is escaping little by little. I can't see anything visible in the hole. I was considering running a very small gauge piece of wire into the hole to see if I can clear whatever is jamming it. Anyone think that is a BAD idea? Alternatives seem to involve pulling the lower unit and taking a crack at it from the inside. I'd rather avoid that given the newness of the boat and the possibility of voiding my warranty by doing that. I'd prefer not to lose a month's boating by taking it to the dealer. Thoughts? Thanks! |
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| Author: | njlarry609 [ Tue May 29, 2007 9:41 pm ] |
| Post subject: | |
Try removing the hose at the speedometer under the dash ( my '95 has a connector just where the black hose comes out of the chase to the dash and is easier to reach). Blow compressed air while someone feels for air flow at the pick-up tube. If you don't have a compressor use canned air and some duck tape to seal the connection. |
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| Author: | 230 Mike [ Tue May 29, 2007 10:00 pm ] |
| Post subject: | |
Your pitot tube is a separate unit mounted at the base of the transom, isn't it? I'd think that if there's something in there it would be in the last 6 inches or so, not halfway to the helm or anything. You could try the wire but be very careful as that tubing is pretty soft. You may have to try to force it out from the helm as suggested, but you don't want to apply very hight pressure to that tubing 'cause you'll rupture it for sure. I wonder if the pitot tube just had a bit of loose or extra plastic that got sucked into the hole and blocked there. Look at it very closely; you can try a wire in the pitot tube but you don't want to enlarge the hole; it could throw the accuracy of the speedo off. If the blockage isn't found in the pitot tube or in the tubing near the pitot tube, I'd wonder if the problem isn't in the speedo itself. Those plastic pitot tubes can be bought for about $6 if it would be easier to just replace it. Just be sure to seal the mounting holes with some 4200 if you do. How annoying. |
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| Author: | bugsdoc1 [ Wed May 30, 2007 12:12 am ] |
| Post subject: | |
| Mine does this all the time.
I just keep cruising and the readings come back to actual speed
There has to be a better system
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| Author: | njlarry609 [ Wed May 30, 2007 10:10 am ] |
| Post subject: | |
I would be afraid probing might drive any blockage up higher. "Backflushing" from the speedometer is easy and should clear out the whole tube and pickup. |
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| Author: | pet575 [ Wed May 30, 2007 10:41 am ] |
| Post subject: | |
Thanks for the replies. Mike, that pitot is on the leading edge of the lower unit, just on the bow side and a little higher than the propellers. Just a hole in the lower unit rather than a lever mounted to the transom. I'm pretty sure it is a piece of soft wood or leaf or something, as there were several pieces of debris floating in the water at one particular part of the lake. I got the heck out of there as soon as I saw it, but unfortunately it was a bit too late. At least I didn't hit a log and punch hole in the hull or anything. I'll try very lightly probing it with a paper clip. If that doesn't work, I'll try the compressed air from the dash. If neither works, I'm just going to leave it alone. I'll be installing PerfectPass on this boat in the next few weeks-which has its own sensor and gauge that will completely bypass this system. That'll show that stupid pitot tube. 
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| Author: | 230 Mike [ Wed May 30, 2007 11:14 am ] |
| Post subject: | |
Interesting setup. Is it hard to get to where the tubing connects to it? That tubing is pretty cheap, but of course routing it through the boat's probably not a trivial job. |
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| Author: | pet575 [ Wed May 30, 2007 11:54 am ] |
| Post subject: | |
I don't know how hard it is. The tube is inside the lower unit, but I've found some stuff on the web showing a possible way to access the tube without pulling the lower unit apart since my original post. Post that is a couple of years old: http://boards.trailerboats.com/cgi-bin/trailerboats/ubb/ultimatebb.cgi?ubb=get_topic;f=6;t=000695 Diagram of housing discussed in thread: http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=880951%2000&ivar=images/CRUISER/880951.00/4.png&inbr=5398&bnbr=120&bdesc=BELL+HOUSING Like I said, PerfectPass will eventually bypass all of this but I'd like to have the stock speedometer working until then (pretty tough to wakeboard by RPM's-especially on a new boat!) and would also like to have it working right if I ever want to go back to using it. |
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| Author: | 230 Mike [ Wed May 30, 2007 1:24 pm ] |
| Post subject: | |
Yeah, if nothing else it would just suck having a brand-new boat with something not working that's right in front of your face all the time  .
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| Author: | pet575 [ Wed May 30, 2007 1:53 pm ] |
| Post subject: | |
Yep. If I were a dirty SOB, I'd take it to the dealer and tell them it has never worked right. Too bad I don't do stuff like that-would work out pretty well this time... |
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| Author: | 230 Mike [ Wed May 30, 2007 5:32 pm ] |
| Post subject: | |
Heck, either way they ought to be taking care of it for you. |
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| Author: | pet575 [ Mon Jun 04, 2007 11:08 am ] |
| Post subject: | |
Update on the speedometer- I was able to get it working again thanks to the help of all of you. I will say that it was difficult, though, because the piece of wood I hit must have been VERY soft. I would estimate that probably 3-4 inches of the pitot was jammed.
So, here is the official procedure for getting something like that opened back up: 1. Pray to whatever you pray to. 2. Make sure you have plenty of your favorite beverage on hand. 3. Get a set of small drill bits (less that 1/4" in size on down), a pair of vice grips, a large paper clip, and have a garden hose with a nozzle accessible. 4. Run the lower unit all the way up and locate the pitot disconnect near the gimbal housing. Unhook the tube by pulling it toward the sky, then turn the pitot plastic assembly that the tube came off of to the starboard side of the engine. It will lift out, giving you access to the hole the pickup tube is connected to. 5. Use the hose and nozzle to blast the debris out. 6. If 5 fails, unfold paper clip and try to clear pickup at hole on leading edge of lower unit. DO NOT force it in, as this may puncture the tube itself. 7. If 6 wouldn't allow the paper clip to move very far, start with the smallest drill bit you can find. Put it in the vise grips and slowly turn counterclockwise by hand (you're "hand drilling" the debris out). Keep the nozzle in place and continuing to apply pressure during this process. Hand drill until you see a steady stream of water. Increase size of drill bit until you have cleared debris. Again, DO NOT force it in, as this may puncture the tube itself. Turn it by hand and be patient. 8. If 7 didn't work, and you have used the largest drill bit possible, go back to the paper clip and unfold it all the way to utilize all of its length. I had to do 1-8, not sure what step 9 is outside of pulling the lower unit to access the tube from the inside. I had the largest drill bit I could fit in the hole (maybe 1/8"? can't remember now) all the way in, and it still didn't clear it. It wasn't until I went back to the paper clip that I could get enough length in there to unclog it. The hand drilling process removed a TON of wood, though. |
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| Author: | 230 Mike [ Mon Jun 04, 2007 11:19 am ] |
| Post subject: | |
Glad to hear you got it out! What a PITA. I'd say the adult beverages would have to be one of the more critical tools on a project like that. |
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| Author: | pet575 [ Mon Jun 04, 2007 11:24 am ] |
| Post subject: | |
I'm just glad I stuck it out. I almost gave up, but the thought of pulling the lower unit just didn't do it for me. I had nearly resigned myself to boating without a speedometer for awhile, which is a nightmare when trying to wakeboard with a novice driver (my wife ). It WAS a PITA, but it will be much easier next time I have to do it-and hopefully for anyone reading this.
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