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I have a question if anyone can help me out. I just purchased this boat two weeks ago. I went to clean out my vst tank and noticed I have two vacuum lines that run to a t fitting. On the other end of the fitting it is not connected to anything. On parts diagrams it shows there is supposed to be a pressure relief valve which then connects to the air intake silencer I believe. Is the relief valve a must have? It appears to be a one way check valve but costs about 120 for it. Any feedback will be appreciated.
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VApor separator tank* -
Those small hoses are there to 'vent' the VST
in the event that pressure builds inside
'presumably' due to the fuel 'boiling off'
perhaps when the engine is shut down, hot after running
We are left to guess at the engineering behind that valve -
clearly it 'limits' the amount of fuel vapor that can escape
but above a certain pressure,
vapor can go into the intake manifold -
where - guessing - it is protected from an 'open spark'.
On some engines Yamaha also uses a carbon canister in that system.
In your shoes, if I didn't want to buy the valve,
I would run the hose down through on of the lower cowling pan drain holes
so any emitted fuel vapor goes outside the cowling
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fairdeal Thank you for your feedback. I just didn’t know if it would have any negative effects on my engine if I decided to not use the valve.Comment
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When that VST venting system causes a problem,Originally posted by B3njammin89 View Post
its usually a 'hot restart issue":
difficulty re-starting the engine, after it has been run hard and shut off for a while -
because the heat inside the cowling 'boils off' the fuel inside the VST
And its one of two scenarios:
1. the engine is 'flooded' by the fuel vapor vented to the intake,
and so has to be cranked multiple times - or the throttle opened wide -
to clear the flooded condition.
You won't see that if the vent hose terminates outside the cowling
or
2. The engine won't start, or starts and immediately dies -
because "all" of the fuel in the VST has boiled off -
and without the engine running,
the mechanical lift pump can't refill the VST.
That is the only risk of removing the valve and venting the hose outside:
you might encounter a situation where you need to use the primer bulb
to refill the VST,
before the engine will start.Comment
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