2003 era 330 Anti-Siphon Valve?

[Halfhitch]

I would add to what seasick is saying that if the starvation situation is the cause of the engines slowing or stalling, then at that time the primer bulbs would be sucked totally flat. If the bulbs are still bulbous while the engines are loosing rpms, then a blocked vent can be eliminated.

 

[seasick]

I agree that a flattened primer bulb generally means that the flow is blocked but not having a collapsed bulb doesn't eliminate a fuel starvation issue. I am not sure why that is but I have seen it. I suppose that if the check valves on the bulb don't seal air completely, the bulb may itself suck air back from the motor direction and not collapse or refill so fast after stalling that you don't see it happen.

 

[wspitler]

The issue becomes where the blockage/obstruction may be. If the blockage/reduction in flow is downstream (closer to the engine) from the primer bulb, it won't flatten. For it to flatten the blockage must be closer to the tank it would seem. In my Yamaha F250, I had fuel starvation from either the LP filter or the VST filter being clogged. I changed both and engine runs great.

 

[SkunkBoat]

I realize that its bth motors but I still go back to the alarms.
My old Suzuki DF140 with the Analog Multigauge would give blinking codes that you could lookup in the manual. I had a problem with stalling when coming down off plane or backing off. Code pointed right to IAC valve (Idle Air Control) .
Not familiar with the C10s but somehow you should find out what code is registered for each motor.

Switching tanks should help determine fuel vent or clog issues.

 

[usmm1234]

I have the exact same issue on my port motor. It happens if I’m idling around a large marina at dead idle. I thought it was a clogged fuel pickup or filters. I changed the Racors and the low pressure filters on the motors. It happened again. I switched tanks and it happened again. If I idle at 1000 rpm. It won’t happen. It might be the lift pump? Motor runs great at all rpm accept 600rpm. And then it takes 5 minutes at that speed for the alarm to sound and then the motor cuts off. I’m going to change the high pressure filters and see if that works. The motors were not quite 3 years old when I bought the boat and only had 79 hours on them. Another words. They sat a lot with stale fuel. I ran the boat 700 mile home from FL so I know the fuel is good now, some times it doesn’t happen? It definitely a fuel Supply issue.

 

[SkunkBoat]

Not sure how the bigger Zukes handle bypass air but along the lines of an IAC valve, it could be choking out as opposed to not getting fuel.
Have you guys tried some cleaner spray in the throttle?

 

[Bayhouse]

Update, still not resolved. Both engines, same tank. Filled the main tank (different Marina) and switched to that tank. Next day, same problem but happened repeatedly for about 5minutes. Following trip, not a single issue over an 8hr day.

managed to check the bulbs after a stall, both were squishy, not flat.

replaced low pressure fuel filters today and drained some gas from VST, looked clean and no water present.

Good suggestions above, have been added to my list.

 

[Bayhouse]

Not sure how the bigger Zukes handle bypass air but along the lines of an IAC valve, it could be choking out as opposed to not getting fuel.
Have you guys tried some cleaner spray in the throttle?

No IAC valve on the 300s, it adjusts itself through a throttle Actuator / Throttle position sensor.

 

[SkunkBoat]

Another thing to check is the position of the bulbs. To work "correctly" the arrow should point UP at the motor. Very often the hoses are too long and bulbs are level or pointing down...especially on bigger boats with rigging tubes where the bulbs are lost in the battery compartment somewhere...
Fuel pumps often compensate for poor positioning of bulbs but sometimes it matters.

 

[Bayhouse]

I realize that its bth motors but I still go back to the alarms.
My old Suzuki DF140 with the Analog Multigauge would give blinking codes that you could lookup in the manual. I had a problem with stalling when coming down off plane or backing off. Code pointed right to IAC valve (Idle Air Control) .
Not familiar with the C10s but somehow you should find out what code is registered for each motor.

Switching tanks should help determine fuel vent or clog issues.

Checked for alarms again today, nothing logged when these events happened.

 

[Bayhouse]

Another thing to check is the position of the bulbs. To work "correctly" the arrow should point UP at the motor. Very often the hoses are too long and bulbs are level or pointing down...especially on bigger boats with rigging tubes where the bulbs are lost in the battery compartment somewhere...
Fuel pumps often compensate for poor positioning of bulbs but sometimes it matters.

Good suggestion, but when I replaced the bulbs ~2 years ago, I also replaced the fuel lines from the F/W separators and added a little more hose so the bulbs are vertical - still that way today.

 

[Bayhouse]

Its unlikely (but still possible) for both anti-siphon valves to go bad at the same time. Since both motors are affected but not always at the same time, I would eliminate for now the kill circuitry. I would lean more towards, a vent issue as mentioned or contaminated fuel. Contaminated fuel could cause clogs or just be a water issue. Second step is to take off the fuel separators and drain the contents into a glass jar. Let it sit 15 minutes or so and see what settles out if.anything.
It was mentioned to run with the fill cap off/open and that is a good/easy way to see there is a venting issue and that should be your first step.
If a vent is blocked it is easy for one motor to die and not the other since each motor probably has a little different draw pressure (vacuum) that will mean that one motor starves before the other. Depending on the amount of vent blockage, one motor mat be able to run without stalling.
Let us know what you find.

About vent blockage, my boat vents the tanks right in the fill cap and when I’m filling up, I can hear them venting so I don’t think that’s the issue. I would expect a blocked vent would also cause more frequent and/or consistent problems...?

 

[Bayhouse]

Agree with seasick. My 330 has two tanks and I run each engine off a different tank to minimize fuel issues. I didn't see if he was running both engines from a single tank. If so switch tanks for one and see if problem follows. If they were Yamahas, I'd bet on bad fuel or clogged VST/LP filters. Several years ago I had a bad water in fuel indicator on my F250, don't know if the Suzukis have that or not.

Yes, the Zukes have the warning alarm as well. See my other post, the problem persists with both tanks, each with fuel from different marinas.

All of the filters were changed before my 1k+ mile trip south and I didn’t have any of these problems...except that damn VST filter which wasn’t on the 1,000 hour maintenance list. I’ve read elsewhere that they are very susceptible to fail if water ever gets into the VST...which happened to me ~3 years ago (Clean tanks since). I will have them replaced soon.

 

[Bayhouse]

Been thinking about this today and realized one thing that I’ve JUST started doing differently is adding Techron to my fuel to try to clean up the valves. I’ve been careful about measurements and only used the recommended volumes.

only other difference, this seems to have started after the most recent 100hr service by a certified Zuke tech. I’ll talk with them as well.

 

[seasick]

I would like to note that although you are sure the vent line is open because you hear the air when filling the tank, it doesn't mean that the cap is venting when you have it screwed on. There is a check valve of a sort in the cap itself. I am not saying that I think that is the problem, but running with the cap off will eliminate that possibility.
Gee , i just thought of something. Make sure you have the vented cap if you have the combo fill/vent deck fitting

 

[Bayhouse]

I would like to note that although you are sure the vent line is open because you hear the air when filling the tank, it doesn't mean that the cap is venting when you have it screwed on. There is a check valve of a sort in the cap itself. I am not saying that I think that is the problem, but running with the cap off will eliminate that possibility.
Gee , i just thought of something. Make sure you have the vented cap if you have the combo fill/vent deck fitting

Vented cap??? There doesn’t appear to be a vent on my caps, need to research this some more.

 

[seasick]

If you look at the underside of a combo fill cap, there is a rubber button kind of thing that lets air get sucked into the tank. The cap itself has an o-ring that seals it so there has to be a way for the tank to get outside air into it.
I believe that the cap for a non combo fill looks exactly the same but doesn't have that little valve..

 

[Bayhouse]

Checked both caps, they have the rubber button things - do they need any kind of servicing?

 

[wspitler]

Since low and high pressure pumps are not typically intermittent, unless the harness is bad, unlikely on twin engines, I'd recommend VST filters, ie, the ones in the VST, also do the LP filter. Just draining clean fuel out of the VST doesn't mean the VST filter are not clogging. I had the issue on a Yamaha V6 and the fuel looked fine out of the VST. Did both engines and the VST filters on both were difficult to blow through as compared to new ones. Problem solved for me. If yours is a fuel issue, and it sounds like it is, then the VST and/or HP or LP pump must be starving. I'm not familiar with the Suzuki 4 strokes, but the fuel flow diagram (below) looks nearly identical to Yamaha?" #11 #27 and #47 might help

 

[Bayhouse]

#47 and #11 were replaced about 120 hours ago so should be fine. It’s that damn #27 that I’m going to need to do. Reviewed the manual, still trying to decide if I tackle this myself or have it done. Replaced the LP filters yesterday.