Explaination of Merc I/O speedometer hose

[poconojoe]

4.3L Alpha 1 Gen 2
Just wondering...how does the speedometer work?
What is inside that hose that goes between the out drive and the speedometer? Oil? Air? Water?
I was in my driveway and had the gauge cluster out of the dash (for a different reason). I happen to squeezed that hose, it felt like nothing was in it.

 

[GA_Boater]

Air, except for the first part going up above the water line.

How it works is the water pressure pushes against the air and the air pressure against a diaphragm in the speedo. The faster you go, the higher the air pressure against the diaphragm, the more the needle moves showing a higher speed.

That's until the hose develops a crack or leak or the diaphragm ruptures. Then the water has no back pressure, fills the hose and goes out of the crack or busted diaphragm. Then it tries to sink your boat.

 

[Scott Danforth]

or if you run aground in the muck, then the pitot tube gets plugged with muck

 

[poconojoe]

Ah! Interesting. Thanks guys!

 

[Bondo]

That's until the hose develops a crack or leak or the diaphragm ruptures. Then the water has no back pressure, fills the hose and goes out of the crack or busted diaphragm. Then it tries to sink your boat.

Ayuh,..... Or ya get that, "I just pee'd my pants feelin'",........

 

[GA_Boater]

Ayuh,..... Or ya get that, "I just pee'd my pants feelin'",........

Ah - I hear the voice of experience. ound:

 

[HT32BSX115]

Ah - I hear the voice of experience. ound:

Un...yeah.......Blowing down the lake at approx 60 mph and water is coming from under the instrument panel and squirting all over me........

I guess I should put a clamp on the back of the speedo so the hose will stopping slipping off!

 

[Scott Danforth]

or simply a zip tie

 

[HT32BSX115]

or simply a zip tie

I seem to remember having a plastic 'zip' on it...........it kept coming off! Probably wasn't pulled tight enough!

 

[UncleWillie]

I seem to remember having a plastic 'zip' on it...........it kept coming off! Probably wasn't pulled tight enough!

Or it was too big for the application.
It is a small hose. You need a tiny 2" ZipTye to get it to conform well.

 

[HT32BSX115]

Or it was too big for the application.
It is a small hose. You need a tiny 2" ZipTye to get it to conform well.

I have some of those, I'll give'r a try! :thumb: