Speed function not working

Wightdiver · 12 October 2015, 14:33

My boat is fitted with a 150 HP Yamaha HPDI. The speed function on the gauges has never worked, which has never particularly worried me, but I noticed the other day it does work at 4MPH!! Reduce to 3MPH or increase to 5MPH and it stops working, but at 4MPH it works.

Obviously all of the components are there for it to work and as winter is approaching I have some time, how would I go about trouble shooting this problem?

Thanks

Andy

Pikey Dave · 12 October 2015, 14:57

Is it a GPS,paddle wheel or pitot tube type?

.....sh1t happens.......

Wightdiver · 12 October 2015, 15:54

Quote:

Originally Posted by Pikey Dave

Is it a GPS,paddle wheel or pitot tube type?

.....sh1t happens.......

Clear plastic tube.

jyasaki · 12 October 2015, 15:56

On the leading edge of the lower unit, you'll find a tiny hole (take a thumbnail and run it along the front edge of the LU until you find a small notch.) That feeds a small plastic or rubber tube that runs up to your speedo gauge. In theory, the water pressure compresses the air in the tube, and the gauge reads that. Most likely, the hole on your LU is blocked. Clean it out with a small drill bit or piece of wire (doesn't matter if you force the blockage further in - there really isn't anything it'll hurt in there.) Should take care of it.

jky

Wightdiver · 12 October 2015, 16:33

Quote:

Originally Posted by jyasaki

On the leading edge of the lower unit, you'll find a tiny hole (take a thumbnail and run it along the front edge of the LU until you find a small notch.) That feeds a small plastic or rubber tube that runs up to your speedo gauge. In theory, the water pressure compresses the air in the tube, and the gauge reads that. Most likely, the hole on your LU is blocked. Clean it out with a small drill bit or piece of wire (doesn't matter if you force the blockage further in - there really isn't anything it'll hurt in there.) Should take care of it.

jky

Thanks, another question, the tube is too long and is coiled up inside the console, is it OK to cut it to the correct length?

Stuart1975 · 12 October 2015, 17:06

Cut it to the right length , then blow back down the tube to the engine to clear it before plugging It back in the back of the gauge - you will tell if its blocked/ full of water by doing this ( can take it off at engine saddle too.

boristhebold · 12 October 2015, 17:21

My yamaha speedo works same as yours, it stopped working a few months ago, i isolated the problem to where the tube from the engine goes through the cabling tube into the transom its got crushed by the otehr cables some how, so water cannot go up the tube properly and hence no reading. Am going to fix it some day when its warmer.

Pikey Dave · 12 October 2015, 17:21

Quote:

Originally Posted by Wightdiver

Clear plastic tube.

Forget it, pitot tube, wildly inaccurate not worth any effort

.....sh1t happens.......

Wightdiver · 12 October 2015, 19:28

Quote:

Originally Posted by Pikey Dave

Forget it, pitot tube, wildly inaccurate not worth any effort

.....sh1t happens.......

More accurate that what I have currently.

Pikey Dave · 12 October 2015, 20:17

Quote:

Originally Posted by Wightdiver

More accurate that what I have currently.

IF you manage to get it working, it won't work for long & it will tell you lies when it does "work". If you really want to get it working, remove the tube from the back of the gauge & blow back towards the engine, you should be able to blow through to the small hole on the leading edge of the gear case. If that works, pull all the slack out of the hose & cut it off, re-attach to the gauge & test. If you can't blow through, you have a blockage or kink somewhere. If it's clear & the gauge still doesn't work, it could be the gauge that's shot.

.....sh1t happens.......

jyasaki · 12 October 2015, 20:31

Quote:

Originally Posted by Wightdiver

Thanks, another question, the tube is too long and is coiled up inside the console, is it OK to cut it to the correct length?

Shouldn't be a problem. Leave enough that you can redo the connection should the end on the barb split or something like that. Alternatively, if you have speed via GPS, break and plug the hoses at the lower unit end and be done with it (I find they're accurate only about 50% of the time or so.)

jky

willk · 12 October 2015, 20:38

Quote:

Originally Posted by jyasaki

(I find they're accurate only about 50% of the time or so.)

As accurate as a stopped clock - i.e. twice a day?

Wightdiver · 13 October 2015, 08:53

Thanks Guys, lots to look at.

Andy

Stuart1975 · 13 October 2015, 11:19

Quote:

Originally Posted by Pikey Dave

Forget it, pitot tube, wildly inaccurate not worth any effort

.....sh1t happens.......

Disagree - my yam works accurately from 4knts to 34 - within 1 of GPS speed (allowing for tides)

Wightdiver · 13 October 2015, 13:38

Quote:

Originally Posted by Stuart1975

Disagree - my yam works accurately from 4knts to 34 - within 1 of GPS speed (allowing for tides)

Thanks, all the more reason to get it fixed.

jyasaki · 13 October 2015, 16:24

To be fair, mine *usually* works, and is fairly accurate (within a MPH or two, bouncing it against the GPS reported speed.) Problem is, when it doesn't work, you have no indication that something is off unless you have something to compare it to. And it can be off from anywhere from 1mph to whatever your speed may actually be. I tend to ignore it and work from the GPS.

jky

grahame42 · 27 May 2016, 08:41

I have compared mine to the GPS and think it's fairly accurate. Which is disappointing as I wanted to believe I was going 5Knots faster :-). Anyway, mine has stopped again - after being stored in a dusty boat shed all winter. So where (on a Ribcraft 585 with a Yamaha 150) does the pipe go to after it leaves the console area? I reckon it is just clogged with dust. Thank you

Wightdiver · 27 May 2016, 09:36

Quote:

Originally Posted by grahame42

I have compared mine to the GPS and think it's fairly accurate. Which is disappointing as I wanted to believe I was going 5Knots faster :-). Anyway, mine has stopped again - after being stored in a dusty boat shed all winter. So where (on a Ribcraft 585 with a Yamaha 150) does the pipe go to after it leaves the console area? I reckon it is just clogged with dust. Thank you

It will follow the other electrical/hydraulic/fuel pipes back to the engine, usually via trunking under the deck? Look at where all of the various pipes connect into the engine, within the bundle there will be a smallish transparent tube.

grahame42 · 28 May 2016, 08:12

Thanks. So is the venturi on part of the leg of the outboard?

jyasaki · 31 May 2016, 04:35

Quote:

Originally Posted by grahame42

Thanks. So is the venturi on part of the leg of the outboard?

Described in the first few posts on this thread. Your blockage is probably going to be on the engine leg, as the rest of the system is closed.

jky