'04 295 Pro XL Fuel Flow (Tank Vent?) Issue With Full Gas Tank

[WCBasser]

This boat is relatively new to me (2.5 months), with a 200 Optimax. On 3 different occasions, on the first run of the next trip after topping off the fuel tank, the engine starts and idles normally, but after just a couple of minutes at high power it surges a couple of times then dies completely. After we coast to a stop and I put it back in neutral, it starts normally and idles well. After we take off and get to high power again it runs 10-30 seconds then dies again. Usually we do this 2 or 3 times. When it dies it sounds like fuel starvation - it surges a couple of times before dying. After going through this cycle 3-4 times, I can start off and run a low (just on plane) power to my first spot and fish. For the rest of the day and any subsequent trips it runs normally at all power levels until the next fuel fill-up, and even sometimes after a fuel refill I have no issues.

I run Don's suggested fuel treatment cocktail (Quikcare+Quikleen+Quikstor) so I don't think it's bad fuel or water in the tank.

I am suspicious of a partially blocked fuel vent line. When the tank is full (little air in the tank), maybe it can't vent fast enough and restricts fuel flow. Once there is enough air in the fuel tank, it becomes a non-issue.

Sound plausible? Anything else I should investigate?

Also, does anyone know how the fuel tank vent system operates on this boat? It's much easier to troubleshoot when you know how it should work. I have a single 41 gallon tank.

Thanks!

[Jumping Jimmy]

Have someone with you open you gas tank cap while it's happening. If operation improves. Then it's the venting. If operation doesn't improve I would get a portable tank and connect it to you engine and test.
You need to determine if you have a boat problem or a engine problem.

[WCBasser]

Good idea! I'll give that a try next time it happens.

[mactlman]

does the bulb go flat like sucking shut?

[WCBasser]

Good question on the bulb - I don't know. The engine usually quits at speed in this scenario, and I'm focused on "landing the boat" safely until we're stopped. After I've turned around to look it hasn't been flat, but by then it's had 15+ seconds to refill without the engine sucking on it. I'll ask my co-angler next time to be sure to look at the bulb right after any engine issues on the next few fill-ups.

Is an engine fuel pump (on a 200HP Optimax) likely strong enough to collapse a bulb?

[mactlman]

Good question on the bulb - I don't know. The engine usually quits at speed in this scenario, and I'm focused on "landing the boat" safely until we're stopped. After I've turned around to look it hasn't been flat, but by then it's had 15+ seconds to refill without the engine sucking on it. I'll ask my co-angler next time to be sure to look at the bulb right after any engine issues on the next few fill-ups.

Is an engine fuel pump (on a 200HP Optimax) likely strong enough to collapse a bulb?

if it is not flat when engine dies, try squeezing the bulb and refilling the fuel rail to see what happens?

[WCBasser]

Well, went out on Friday with a full tank (but this time was careful not to top off - stopped fueling the first time the gas nozzle cut off). About 2-3 minutes into the first run of the day (about 5000 RPM), the engine died as before. My co-angler got a quick look at the bulb as we coasted to a stop - it was not flat and looked normal. Once the boat stopped, I had him reach over and open the fuel filler cap to vent the tank, just in case this was indeed the problem. He did so, then replaced the fuel cap and tightened normally. The engine restarted immediately and ran normally the rest of the day (4 more 10-minute high power runs). So, I still believe it may be a fuel tank venting issue, but not sure.

I'm thinking the next time I fuel up I may intentionally fill it to the top. Once on the water, I'll loosen the filler cap so the tank can easily vent that way. If the engine runs normally, I think that's pretty good evidence and I'll start taking things apart to look for issues with the vent line.

Any other ideas? It seems a bit surprising to me that venting the tank once was enough to resolve the issue, but since I didn't top it off maybe it was.

[mactlman]

have you tried squeezing bulb when it is trying to die? do you pump up bulb first thing in the morning or before launching?

[WCBasser]

I haven't tried squeezing the bulb - it usually surges just once or twice then dies cold. No time to get to the bulb before we're coasting to a stop. It's also a little awkward to reach from either of the cockpit seats in my boat.

Yes, I always squeeze the bulb until it's firm just before launching. It doesn't take much. Even on the first start of the day the engine fires up after just a couple of seconds on the starter. Interesting data is that this has never happened if I've run more than 10 minutes (above 4500 RPM) on a new tank of fuel. The rest of the time the motor runs flawlessly.

[Kb444fishing]

It's indeed running out of fuel I can't imagine it being very good on the engine v

[WCBasser]

Agree. That's why I want to get this resolved ASAP.

[Kb444fishing]

Not sure but if the vent wasn't working it would be harder than normal to fuel. They do spit out but I had a buddy leaning over my vent hole one time and it would accept fuel. List your seriel number and ask again. Joe or don knows the most. Don says to pump bulb every start which I don't get cause nobody does but that's what he says. My guess would be in the fuel pumps. I don't know much about them but I think you have a high pressure pump and maybe a low pressure. List it in the Mercury forum. Could also be bad fuel line caused by ethonal in the past.