Honda BF45 lower replacement - weird tube?

My honda BF45 had a cracked lower, so i bought a new one and busy installing it, but for some reason there is this odd tube thats plugged on the old lower that I cant seem to figure out what to do with?

can I just plug the hole in the lower unit with a teflon screw plug?

The workshop manuall calls for a "sensor plug" [See No. 15 in picture].. but the tube that is connected to it just has a closed plug nipple [see No.8 in picture] on the other end.. effectively plugging the tube?

its not connected to anything on the other end?

WTF? the new lower doesnt have anything connected?

any ideas?

Not weird at all in my opinion.................------Most motors have that tube and it is for a speedometer !!!!

Interresting, i didnt know you could tell speed based on water pressure of the water pump?

I thought maybe its for water pressure?

can i just plug the hole?

I have a GPS based speedometer..

Thanks for the help!

No, no ---That is not how it works at all.-----There is a wee hole in front of the lower unit and as the boat moves faster and faster there is more pressure put into the wee hose.----Nothing to do with the water pump either.-------This saves mounting a seperate pitot tube on the transom !!!

ah! That makes sense.. thanks so much! very new to marine motors.. done the basics like annual service, but nothing like lower units yet.

so i take it i can just plug that hole then?

Typically given the French name "PITOT" tube.(pronunciation: "pee-tow" or "pea-toe") It captures water pressure entering the front of the outboard through a calibrated hole and directs it to a sensor that "interprets" the force as speed.

They are used extensively on aircraft too in the same manner. Only they capture and interpret air pressure entering the orifice.

With the advent of GPS and other electronics, I think we will see their use slowly abandoned over time. They ARE problematic as they get plugged up and "contaminated" and have to be cleaned and maintained.

They have actually been blamed for many aircraft mishaps when they freeze up at high altitude.

So....yes....plug the hole.

Thank you, jgmo! much appreciated.

lower unit replaced with new, annual service done and ready to rock the weekend!

"Pitot Speed" is speed through the water and "GPS Speed" is speed over the "Earth", so if there is any water "Current", an error will be introduced. So if you were measuring your boat's performance, this could alter the results. GPS Speed is far more accurate for "When do we get there?".

Almost all aircraft have electric pitot heat that the pilot/s have to turn on before take-off. As the aircraft climbs with a frozen pitot, the indicated airspeed increases, no-matter the actual speed. If the Air France Pilots (3) had noticed their GPS Speed (or remembered to turn on pitot heat), it may have prevented their tragic loss on that flight in 2009.
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