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I have a 2001 Glacier Bay 2260 (new hull design) cat with Yam 115 4 -strokes. About 110 hours. Counter rotating port engine runs fine for about 30 minutes. After crusing and coming to no wake zone or fishing area, port engine bogs down, runs rough, sometimes stalls, does not want to start unless I put in neutral, advance throtte. Eventually breaks out of problem and runs fine. Or after running 4200 RPM for awhile, I will go at 1200 RPM for about 5 minutes, port engine will bog down to about 600 RPM and will run rough for about 3 minutes and then seems to find its way out, get back up to 1200 RPM and run fine for awhile. Then it cycles all over again. Three trips to the dealer, they have changed the Yamaha engine computer twice, and a couple of components in the injector area. Every time I check the plugs, they are always black and sooty, even after only a few hours with new plugs. Dealer says they talk to Yamaha, but the problem still persists. I've had this problem since last fall. Anyone have any ideas ? Thanks.
Sooty you say? Both sides or just the port side? Sounds a lot like rich engine and the plugs are not reaching and/or maintaining their self-clean temperature That or the engine is running cold. Has anyone checked to see if the thermostats are stuck open? Does the engine computer use a water temperature sensor? The sensor could be telling the computer to run a fueling strategy for a cold engine. This would tend to overfuel the engine and might soot up the plugs. If the thing has an O2 sensor it might be an area to look at. O2 sensors control mixture in so equipped fuel injected engines.
That rough running thing might also be spark related. Crankshaft sensors control the firing. Make sure the sensor is close enough to the flywheel to pick up a signal.
Now there's the throttle postion sensor. It tells your computer where you have throttle. It reads in values from 0 - 100. If it has a bad spot, it will play hell on your computer and won't necessarily trip a "check engine light". Do both engines get the same economy or does the port motor suck more fuel?
You say it's only one engine? I'd suggest swapping suspect parts side to side and try to move the problem to the stbd motor. Keep us posted
loose cannon
as far as your problem on the engine I an sorry but I have never seen any act quite like that. I would like to know if when you are running along at above 3500 rpms and just kill the engine without returning to neutral are the plugs still dark.if the plugs are still dark at this time be sure to let the service manager know this so he will know that it is rich at the top end not just at low rpms. you need not worry about the O2 sensor the f115 dosn't use one.the throttle position sensor is not A 1 to 100 reading it returns a voltage to the computer.the computer sends out A 5 volt signal to the TPS. sensor the TPS.sensor then returns a voltage of aprox .5 volts at idle up to aprox 4.5 volts at full throttle you are correct about doing A TPS. sweep to test the sensor for bad spots.
Thanks for the ideas. I've sent them to the dealer and he is forwarding along with his records to Yamaha. One other wierd thing, one day I noticed a fuel drip from the port engine. Upon taking the cowl off and tilting the engine forward, a trickle of gas came out of the air intake. I took off the screen and stuck my finger in there and could feel wet on the bottom. Any ideas ?
Fuel drip ? Wet intake ? Boy are you running RICH !!!
Most EFI's (I'm not a Yamaha technician) do NOT use Throttle Position (directly) in calculating fuel. Fuel is calcualted by measuring/calucalting Air Flow from a Vane Meter (I don't think the 115 uses this), a Mass Air Meter (maybe) or by measuring mainfold pressures vs atmospheric pressure and doing some fancy calculations (speed density). Which ever method Yamaha uses, it sounds like this sensor is bad.
A quick check the dealer could do is to locate the signal wire for that sensor and compare the voltage on the port vs starboard engine while running at closed, part and wide open throttle.
(The TPS is used to "enrichen" the fuel while accelerating i.e. "pump shot". It is also used to determine, close, part and WOT. These modes change the way spark is calculated)
I did some experimenting today. I put in new plugs and ran the boat for about 50 minutes at 4000 - 5600 RPMs without using it much at idle or low speed. It ran fine. I removed the plugs and the center was white and there was some black soot on the ring of the plug.
I then put the plugs back in and ran the boat for about 50 minutes at 700 - 1200 RPM. I did not get any symptoms of engine bogging down. However after returning and raising the engine to get to plugs, I noticed 3 or 4 ounces of gas driping out of the engine thru the air intake. Upon removing the plugs, the center had turned black and they were oily looking.
I am going to forward this to the dealer and Yamaha, but I welcome any ideas on what these conditions indicate.
Thanks to Hull Truth, Yamaha, and my dealer, seems the problem has been solved. Thanks to Yamtec for suggesting a problem determination technique. Thanks to Yamaha for watching the Hull Truth and e-mailing me with concern and an action plan. Thanks to the dealer for tearing down the intake/fuel injection assembly and finding a component that was not seated correctly at manufacturing time. (something to do with needle valve/float assembly). At any rate, Yamaha and the dealer hung in there to fix it. Thanks to all that suggested a solution. The internet can be a positive force when used correctly.
