TOPIC: Trying to help my neighbor with his speedometer

The guy that lives right across the street has an 05 Key Largo 160 (looks like a Boston Whaler) with a 60 Yammerhammer on it. He came back from the lake today and walked over to ask for help, as he often does. (Sometimes just to shoot the bull, mind you.) Not that I mind helping, but have you ever been right in the middle of a project.........I digress.

His speedometer is "stuck" at 22mph. I noticed Friday that the lake had a lot of trash floating in it, so I told him he probably lodged some in the pitot tube. He had a confused look on his face, so I showed him where and what it was. He commented that his boat didn't have anything mounted on the transom but the transducer for his fish finder.

We walked back over to inspect his boat, and sure enough, no pitot! The transducer has no holes for water pickup, nor any tube running up the transom as I'm accustomed to seeing. There is a pickup in the hull just forward of the stern for his livewell, but no pickup there either. We searched the entire hull and found nothing!

We pulled the access panel on the center console to view the back of the speedo, and it DOES have a tube running down the side going under the deck, but where from there?

There is one hose coming from his lower unit on the motor, but that would be for his water pressure gauge, (dealer installed at purchase) right? Any thoughts, suggestions, comments welcomed, as always.

The only thing I could suggest was disconnecting the hose at the back of the speedo and blowing compressed air back thru the line. Didn't offer to help with that, since I've been standing on my head all day rewiring the dash on the Starflite, shame on me.

start at the gear case pitot opening with a small pin or a paperclip and see if it has blockage. If not, Pull it at the gauge, it should drop to "0" . If you do this and it does, it's in the line and back blow it. It dose have blockage. If not got out soon, it will mess up the anode in the sped-o.
The tube has many connectors that are smaller ID than the hose. Never try to blow it forward. Always backward via the path the blockage got in.

Mark,

Not a bad thing BUT you are still thinking in the "stone ages".

There will be a small hole at the front of the gearcase a few inches above the fwd end of the prop shaft. That is the speedo pickup. The hose to it should run down over the transon and perhaps down thru the steering tube.

There are a few advantages to this system;
1) No holes in the transom.
2) No pitot tube to get broken off - and the do eventually break just from deteriorated plastic.
3) More accurate display. The water is truely hitting it much more straight on than what hits a pitot tube on a deep V hull. Take a deep V (your 178 is deep enough) and take a ride in calm water at a steady speed. Just turn the wheel 1/4 turn each way & watch the speedo move several MPH.

As for the water pressure gauge, it may be an electronic display. Take a look & see if there is a hose connected to it.

Thanks for the responses, y'all. I did warn him about not blowing compressed air up into the speedo, Heather, hopefully he was listening. I'll give him the rest of the info tomorrow, thanks again to both of you for the updated info.

Of course I think in "Stone Age" terms, Jim, I'm old and all I work on is antique equipment. I told him up front I knew very little about his "new fangled" machine. That blew up the spell-checker! (Not hating, but not jealous either.) It's actually a pretty nice little fishing boat, lot's of bells and whistles.