Sudden engine shutdown

[FinAllie]

Hey folks,

I have a 2004 330 Express. 2013 300 Yamaha 4strokes. They purr like kittens at all RPMS. Everything is great except for one pesky, hard to duplicate issue. This issue only happens when I'm climbing out of the hole and the bow is up so I suspect that is has something to do with the deck angle. It does not happen at WOT or any time after I'm on full plane. It doesn't happen at idle or any RPM low enough where the bow is down.

From idle in gear, as I advance the throttles to come up on plane, sometimes at about 3500-4000 the engine(s) will suddenly shut down. Sometimes its the left motor, sometimes its the right motor. Sometimes its both. They fire right up afterwards and can run the rest of the day just fine. I have tried about 15 hole shots trying to get it to do the same thing and it won't repeat itself consistently. It just happens maybe 1 out of every 20 times. I checked the fuel filters, I'm running new fuel, it does it on both tanks, and I have more than half tank of fuel when it did it the first time.

Ideas appreciated.

FinAllie.

 

[seasick]

I am not sure what is going on but next time it happens, immediately turn off the ignition for the troubled motor. Come to a stop and remove the cowling. Look at the gas filter to see if the bowl is full, empty or in between. If you can't see the filter insides ( not clear) try pumping the primer bulb. It should not be soft.
It is possible that the issue is not angle per se but a restricted fuel flow that shows up when gas consumption rate is high as it would be when getting on plane. Also check you primer bulbs to make sure that were not installed backwards.

 

[Mustang65fbk]

My uncle had a similar issue to this with his old boat where both fuel lines/bulbs had a few small pinholes in them that would allow air to get through and into the fuel system, especially when accelerating. Enough air and not enough gasoline would then starve the motor(s) and would shut either one or both of them down upon hard acceleration. He swapped out the fuel lines and didn't have the issue after that.

 

[FinAllie]

I'll continue to check those ideas out. Just a note, I don't have the issue when running WOT or high RPM where fuel flow is highest. Only happens when around mid range RPM.

 

[loubeer]

I have heard of the fuel lines delaminating and causing the inner liner to collapse choking off fuel flow. Not sure this is your problem, but if your fuel lines are older, could be.

 

[Sardinia306Canyon]

A fuel problem is possible but quitting engine should stutter before stopping,
if that is not happening and engine just quit then i would check electric connections it may be that with bow high something becomes loose and let engine stop.
However, pull the cowlings and verify, if the engine mounted fuel filter becomes empty then a fuel problem becomes more likely.

I have a similar problem, but only on the 2011 port engine, after trolling or idling for a while and then accelerating to plane port engine rises to 4000 rpm and then lower rpms and rpm's will not rise, but engine will not stop. The only way to overcome that is to switch off engine and start her again and then all is fine. My ex boss and best friend who has a ship yard and knows Yamahas very well told me that the LP fuel pump may be the problem and not filling the VST quick enough to keep up with hard acceleration, but when turning the Key to On position the engine LP pump start to fill and solve the problem.

The test for that would be having one person to pump the primer bulb when this happen,
so you may try the same and as written, check if engine fuel filter stay more or less full.

Chris

 

[seasick]

Another thought. Do you have anything hanging off of the kill lanyard? Have you tried wiggling the cutoff gizmo to see if the motor dies?
Also, did you happen to notice if when the motor dies if the gauges are off of in self test mode?

 

[Sardinia306Canyon]

Another thought.

Yep, and a good one.
A kill switch with problems could lead to same problem, but it's a bit wired that it happens some time to only one engine.
But could be not the kill switch itself, but a bad connection on the wires from the kill switch to the harness, or inside the harness.

Chris

 

[FinAllie]

I cleaned off all the battery terminal connections and have run the boat twice now without the problem occurring. Since it's very intermittent I can't say that has solved the problem just yet. I tried the kill switch idea. I jiggled it excessively and nothing happened. When I pulled the lanyard both motors quit as they should.

 

[seasick]

You might be on to something.
Are you batteries held down with straps or metal clamps? Are the terminal connected with wing nuts or machine nuts?

Since both batteries died and if the problem were the connection AND you run each motor on a different battery, the electrical issue would be on the negative side. It would also be the negative side of the battery that both batteries are common to. Phew!
In other words if the issue were a loose or bad ground connection, the motors that share that connection would be affected.