Tell Tail question LF115TXRB

[99yam40]

I still do not get where the air comes from the OP talked about

[gtreanto]

two thoughts:

1.


yes - but only after it passes through the fuel cooler

So if the fuel cooler passageway (or any of the tubing) is occluded,
the flow will be affected

2. Here is the exhaust cover viewed from the outside



From the back - "inside" -

its clear that the "Tee" is adjacent to the pressurized side of the "poppet valve"

If the poppet valve is allowing flow - "dumping' -

then the water will "take the path of least resistance" and not also flow to the telltale

I know the fuel cooler is not clogged since the tell tail flows when the boat is running on muffs or in the water. The issue is when the water flows from the flush port only. This is the only time water flows from engine top. IE from the outside T connection.

Fairdeal you make an interesting point about the poppet valve. If there isn't enough pressure to cause the water to flow down the T then you would get the hissing sound I hear. This would be from the water flowing through the straight part of the T. When I put a wire in the bottom part of the T it blocks the flow from going straight and thus I get water coming out of the bottom. Same holds true when running the engine with muffs or in water. In those cases the flush port is blocked causing enough pressure for the water to flow out the bottom of the T.

Is the poppet valve behind the cover that has the black cable clamp on it? What is the purpose of the poppet valve in this application?

[TownsendsFJR1300]

I know the fuel cooler is not clogged since the tell tail flows when the boat is running on muffs or in the water. The issue is when the water flows from the flush port only. This is the only time water flows from engine top. IE from the outside T connection.

Fairdeal you make an interesting point about the poppet valve. If there isn't enough pressure to cause the water to flow down the T then you would get the hissing sound I hear. This would be from the water flowing through the straight part of the T. When I put a wire in the bottom part of the T it blocks the flow from going straight and thus I get water coming out of the bottom. Same holds true when running the engine with muffs or in water. In those cases the flush port is blocked causing enough pressure for the water to flow out the bottom of the T.

Is the poppet valve behind the cover that has the black cable clamp on it? What is the purpose of the poppet valve in this application?

Yes it is... It releases excess water pressure (usually at higher RPM's). If stuck open or leaking, you won't get the full water pressure to the power head.

Part #28 for your engine:

http://www.boats.net/parts/search/Ya...201/parts.html



My poppit valve, spring and cover (and the engine is flushed after every outing-shown is
about 10 years old). You should be looking at the rubber ring in the block and for any corrosion

[gtreanto]

Yes it is... It releases excess water pressure (usually at higher RPM's). If stuck open or leaking, you won't get the full water pressure to the power head.

Part #28 for your engine:

2006 and Later LF115TXR Yamaha Outboard CYLINDER CRANKCASE 1 Diagram and Parts



My poppit valve, spring and cover (and the engine is flushed after every outing-shown is
about 10 years old). You should be looking at the rubber ring in the block and for any corrosion

Thanks.. I just ordered the grommet, spring, pressure valve and gasket. Once in I'll update the thread if that fixes the issue.

[gtreanto]

I replaced the poppet valve and no change. I am suspecting there is another place where there should be a restriction to cause enough pressure for the tell tail to work. I am wondering if the water pump could be worn a little to still work but have enough blow-by during a flush to cause low pressure. I am going to replace the water pump this fall. Right now I have no other ideas.

[rodbolt17]

it is normal.
it is called the Venturi effect.
most all F1115 motors I ran of that design wont have a tell tale when using the flush port.
the water rushing past tends to pull a small vacuum on the tell tale nipple.
inserting anything in the T breaks it and now you have water flow.

it is working as designed.

[gtreanto]

it is normal.
it is called the Venturi effect.
most all F1115 motors I ran of that design wont have a tell tale when using the flush port.
the water rushing past tends to pull a small vacuum on the tell tale nipple.
inserting anything in the T breaks it and now you have water flow.

it is working as designed.

If the starboard engine did the same I wouldn't have chased this issue for so long. Anyway thanks for the comments rodbolt I'll leave it as is..

[99yam40]

My guess is some build up in one of the units to stop/prevent it from happening, but who really knows for sure at this point.
maybe you should take both apart to see if you can find something different

[gtreanto]

This is not a clogged something issue. I would put it in the category of a leak issue. Something is allowing water to pass easily so there isn't enough pressure to force the water out the tell tail port. Or as rodbolt and I have written the shape of the T is causing a venturi. Since this is not causing a running issue I am going to drop the exploration.

[99yam40]

I agree,
I just was saying the same as you, not plugged just a slight restriction in one that the other does not have is the reason one pees but the other does not.
very weird that the noise you hear being a sucking of air into the tell tail.
And that it has been seen on other motors

[gtreanto]

Here is a video of the engine running with the tell-tail line disconnected. You can hear the suction. Hopefully the link works.. http://drive.google.com/uc?export=vi...QnuznAlV1b48pA