99 Yamaha F100 Is the hose on the front a vent??

[speed_demon]

There is a plastic nipple right in front of the shift shaft on the lower unit that appears to be a vent that attaches to a hose run up under the cowling. As far as I can tell it doesn't vent anything. I tried to blow through it but it's sealed. What exactly does this port do? or do I have a blockage? The unit is disassembled.

 

[Bosunsmate]

Re: 99 Yamaha F100 Is the hose on the front a vent??

Im pretty sure that is somesort of expansion tube for the LU so as the gearbox heats up the air can expand into it. Mine is blocked too and the LU is doing a real good job of keeping out water intrusion so i think it could be part of quite a good system

 

[99yam40]

Re: 99 Yamaha F100 Is the hose on the front a vent??

Only tube running to top from lower unit I have seen was for speedo, but have not looked at the F100

 

[Capt Ken]

Re: 99 Yamaha F100 Is the hose on the front a vent??

It's the speedo pickup

 

[speed_demon]

Re: 99 Yamaha F100 Is the hose on the front a vent??

How does that work? It was removed when I got the motor (project). In the diagram it just looks like a hose that terminates half way up.

 

[Silvertip]

Re: 99 Yamaha F100 Is the hose on the front a vent??

Terminates half way up :"where". That motor has a pitot and that plastic tube runs (or should run) up to the back of the speedometer head. As the boat moves forward, water pressure compresses the air in the tube and the increased pressure unwinds the Bourdon tube in the speedometer. No water actually flows in the tube. If it did you would have wet feet. A pitot speedometer is nothing more than a pressure gauge. Look at the back of the boat. If you see a white plastic deal on the transom with the tip of it pointing down into the water, that's a pitot as well. The speedometer tube must therefore be connected to either the pitot on the engine or the external unit.

 

[speed_demon]

Re: 99 Yamaha F100 Is the hose on the front a vent??

Thanks. It looked like a terminator in the parts manual but it must just be a coupler. I would have never guessed.