Yamaha 250 issue

[abl1111]

Got a question for you guys - it's on behalf of my brother who is running (2) yammi 250's with 300 hours and has been having the same issue for 2 years; either engine will suddenly die under way. The priming ball will be totally sucked in. Typically happens after he refuels - can be either engine. Happens randomly. What's he tried;

New fuel lines from tank senders thru to engines including priming balls
All new fuel filters within each engine.
Fuel tank polishing 2x ( after the first cleaning, an engine stalled and the guy came back did it again )

After 15 hours of use, it just happened again..

I think something must be in his tank still, moving about and randomly and temporarily clogging either pick up.

Engines are professionally maintained - the Yamaha guy thinks it's something in tank. With all the baffles etc how can you clean 100% ?

Thoughts ?

[dginge]

I had a similar situation. I had a kink in the vent hose. To me its sounds like it's getting all the fuel it needs until something happens all of the sudden. It could be a partial kink until you hit the wrong wave and then it's fully linked. It's common

[Old'sCool]

Anti-siphon ball at exit fitting on tank

[NoBones]

Vent line is clogged / blocked....
Blow air through ...
Spiders, mud dobbers, lizard, who knows what could be stuck in there...

[DonV]

Ya know Bones those little mud dobber buggers, which are a PIA, clogged my Optimax pee hole, that will set off the high temp alarm in like three minutes.

[abl1111]

It's got a perko filler with an integral breather vent. The vent hose seems unkinked and when detached from the filler, you can blow thru it with ease into the tank.

Not sure if there is an anti siphon ball ?

When this issue happens and primer ball is sucked in - when opening the fuel filler cap, this has no effect on the primer ball. If a vent issue, 'you would think' the primer ball would pop open ?

It's a damn gremlin...

[caper]

Had same issue years ago - when I filled the tank - I added gas until it was in the fill tube - turns out that got some fuel in the vent line and that caused the stalling problem. I had to learn to only fill to about 7/8 of a tank. If you overfill, removing the fill cap will alleviate the problem until enough fuel is burned to clear the vent hose.

[DonV]

OH NO!!! Not the Perko fill cap!! I've got one on my second boat, what a total PIA!!! You have to put gas in very slow because if too fast it blocks the air coming back out the vent, you can not put gas in with a can unless you use a funnel in the large hole so it will vent and number one it will leak water in the tank if the O-ring is not in place. Hate those fillers!!!!

http://perko.com/catalog/fuel_system...-_angled_neck/

[abl1111]

Troubleshooting the system based on some of your input. The fuel filler and the vent line are both in the very back of the tank which seems like a bad idea.

I can see how with a 3/4 to full tank that the vent and fuel fill lines would be submerged under fuel while under way ( the gas would all be aft ).

This could create a vapor lock as the fuel would be obstructing the ability of the vent to breathe. And, its possible that the engines fuel pump would suck the primer ball in, starving for fuel.

However, you would think that once the boat was stopped - the fuel level would normalize. And, when the fuel cap, which also houses the vent line breather were opened, the primer ball would fill back up - this is not the case. The primer ball stays sucked in. The only thing that remedy's this has been to wait and sometimes, infrequently if you turn off and re-start the other motor - the ball will normalize.

We checked the Perko breather caps ability to breathe when closed - it does.

Is there anything else we're missing ?

If we could confirm it's one thing or another, then we'd focus there - but for now, we're at;

- something randomly clogging the pickups at different times even though the fuel tank has been polished twice
- a vacuum issue due to venting problem

If I knew it were a venting issue, an option could be to empty tank and have a new vent hole drilled into the tank more forward.

Any new ideas based on the above ?

[abl1111]

The other idea is to switch the 10 micron water / fuel separator to a 20 micron one ?