I've got a pair of 1998 250 OX66's that I've owned for 3 years. I've got to know them pretty well, but this one's got me scratching my head. Over the season, the starboard motor will cut out randomly (completely stall, like the key was switched off). This seems to happen at any RPM...maybe just idling through marina, or during cruise. It doesn't bog or surge, just shuts down. I can usually get the motor going again to get me home. When I get it going again, it runs fine throughout the throttle range, but then again might cut out without warning. In the past after one of these incidents, I've pulled the VST tank and cleaned real well, which has seemed to solve the problem...it usually goes away for several weeks. Happened again yesterday. This time I came home on one motor, although I did get it going at the dock again. I pulled the VST. While I notice there's a little crap on the VST filter, it doesn't seem like there's enough of an obstruction anywhere to cause such a sudden shut down. The needle valve looks OK, and moves freely. I'm kind of wondering if the high pressure fuel pump is on the fritz. I put 12V across it real quick and it runs. Could it be going bad and cut out occasionally?
I've kept up on what maintanence I'm aware of: New low pressure pumps this year, cleaned and checked 02 sensor, new plugs, new fuel filters, thermostats.
Another symptom that I thought was unrelated is that I've noticed a little fuel surfacing at the dock, looks like its coming up through the exhaust. After checking the compression and replacing the low pressure fuel pumps, I assumed it was a stuck fuel injector on one of the cylinders that shuts down at idle / low RPM rpms. My thought was to send them out for testing / cleaning over the winter.
This forum has always been one of the best I've found (Thanks Rodbolt!). I haven't turned up anything quite like this through searches, so any thoughts or suggestions for troubleshoting this thing would be greatly appreciated.
Well, if it acts like a switch is thrown, just blink and it's dead, then it's electrical...and I'm sorta thinking that you have a connection(most likely ground) that isn't always good....the randomness of the problem occuring leads me this way, either no ground where it should be or kill circuit cutting in when it shouldn't....most people don't suspect wiring if it 'looks' ok....you may want to run voltage drops thru charging system first, it is EFI after all and wants good 12 volts....Rodbolt will have to help you from here, I'm stumped.
Thanks for the reply. It makes sense that its electrical. I did notice that the alarm sounded about a second before the motor quit. I'll start working my way through the system.
OK. So I put the VST back on and it fired up and it ran fine. I have not been out to sea with it yet, so we'll see what happens.
A couple things I noticed while I was probing around that weren't right:
1. The battery terminals on two of the batteries were pretty corroded, more on the + terminals. I cleaned these real well. Does the OX66 have any trips that will shut down the motor if it loses contact or ground at the battery?
2. I pulled the fuel rail just because I was interested and cleaned the screens at the injectors. There was a little crap in each. However, In taking off the intake cover, I noticed there was a bunch of 2 stoke oil collected in the bottom of the cover and in each of the intake ports around the throttle plates. I've never noticed this before, but have had no reason to take the intake cover off lately. Is this a symptom of something else?
If you have cleaned the VST and solved the problem in the past, then it sounds like you are on to something. could be that the injector screens are now dirty so when the VST is marginally dirty it's not supplying enough fuel. Also, I didn't see that you cleaned the fuel pressure regulator screen. The fuel pressure reg is on top of the VST. If the VST filter has been dirty in the past, the fuel pressure regulator screen must be too. I like your idea of having the injectors checked this winter.
Have you found anything? I have a similiar problem where the engine shuts down but will immediately restart when you hit the key. Checked all grounds and wiring.
That oil pooled up in there is a normal thing, they all do, from being tilted up and the excess gas and oil leaks out a little, gas evaporates, oil sits....I would like to make sure we're talking about 'sudden'....if it dies in three seconds or INSTANTLY....as to the question of a trip or something on engine if it loses batt. power, EFI will simply NOT run without 12V power from battery. Carbed motors will, EFI can't. Yes it has a stator, no it won't run off it. You found some corrosion....I still don't know if you are in salt, I'm gonna presume(I know, I know) that you are. If all the stuff in boat is 1998, you could have corrosion in several places that could cause this....I would run the motor on a keyswitch and eliminate boat harness, and after ten years in salt, the batt. cables themselves may be green in middle of wire even(one little pinhole in insulation will do it, seen it), and check the grounds(ALL) on engine....has to be electrical if INSTANTLY dies...I'd post again and ask in post for RODBOLT....
Thanks for the reply Yamahamarinetech40. I haven't had a chance again in a couple weeks to run it. I spent some time cleaning some obvious connections and spraying with "Corrosion Block". I took it out of the water for the season this weekend, and during the 5 mile trip, it cut out 3 times. Yep, its sudden (like the key is switched off), and yep, its salt. I can usually get it running again within 5 minutes.
The batteries are good, guages read 13-14 volts during run over. This one scares me a bit as its so intermittent. I'd like to hope I can solve it this winter during its lay-up...Rodbolt, I need you!!!
alarm just before shutdown?
lets review the methods to sound the alarm on that yamaha, low engine oil,RPM reduction but no shutdown, trying to start while the stop lanyard is engaged,not the case here.DES switch engaged,could be the case here but the alarm should keep sounding if it was a simple stall.overheat,there again RPM reduction but no shut down.
water in the fuel,only if you have retrofitted with the water detect filter cup.
low battery,could be would be what I would lean towards.
if your digital gauges stay powered up and the engine cranks over normally then I would not chase battery cables or the red powerfeed to the keyswitch, also would not chase the key switch or dash wiring.
there is a splice just aft of the engine side 10 pin main that can go bad.
what I would do is hook up the fuel pressure test gauge and a voltmeter.
voltmeter positive to either the pump red lead or any of the injector yellow red wires. black lead to ground.
could be several things happening here,loss of fuel pressure due to pump shutdown or restriction can lead to a sudden almost key off type stall.
a bad splice in the engine harness can allow the main relay to disengage shutting down the ECU,fuel pump and injectors.
bad ECU ground leads can interrupt the current path for pump run,injector on and sensor voltage.
but your going to have to have the test equipment on the engine at the point of failure to isolate it.
can be fun
Thank you Rodbolt! I have my marching orders. Question: If the high pressure fuel pump was on the frits, would it go bad intermittenly like this? I tried to listen for it with turn of the key on last run after stall, but was alone, it was blowing, and I couldn't hear. I have twins and might also try some part swapping.
Also, don't know if you caught the fuel in the exhaust / water symptom? I have it in my head that one of the injectors on one of the dead cylinders at idle is pumping fuel. Compressions is good, and when this motor is running, its perfect. Could this be related?
Yamaha 250 Ox66 Cuts Out
Re: Yamaha 250 Ox66 Cuts Out
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