1999 Yamaha 0X66 vmax 200 cutting out!!

[hvtexskeeter]

I posted this in the non modified yamaha board and reposted it here to get more exposure. I have a 1999 yamaha ox66 200 vmax fuel injected engine on a 1999 zx202 skeeter that I had the powerhead replaced on about 40 hours ago by hydrotech marine. It has ran flawlessly for 40 hours after the powerhead replacement and everything was great. It now has a problem of cutting out at about 3000 rpm and above when the engine is loaded going down the lake. It runs fine in the driveway under no load at various rpms. Checked compression on engine all cylinders check good with 125-130 psi on all cylinders (high compression hydrotech heads hydrotech phase 2 kit) Here is a list of things that have been done to troubleshoot and or fix the problem with the engine: 1. First thing I did at the lake when it first occured was replace the spark plugs with new plugs, no help. 2. replaced all fuel lines with gates ecofuel compatible fuel lines from the fittings at the fuel tanks to the low pressure fuel filter on engine, no help. 3. Changed inline water seperator with new yamaha cartridege, no help. 4. drained all fuel from tanks and replaced with fresh fuel and ringfree plus, no help. 4. Changed low pressure fuel filter at engine and removed VST tank and opened up and cleaned high pressure fuel pump filter, which was clean already, no help. 5. lake tested boat with fuel pressure gauge connected to fuel rail and 02 sensor test harness connected to volt meter. Fuel pressure reads steady at 36 psi, good per manual. 02 sensor reads .3 volts to .8 volts and varies quickly depending on engine speed and load, seems to be ok. but engine still cuts out, no help. 6. connected spark plug tester (cheap one that looks like a spark plug) and ran engine in driveway. spark appears good at each cylinder with the tester at idle under no load. Engine runs kinda rough on 5 cylinders but does ok. Havent been able to figure out how to check the spark on the engine while lake testing the boat. 7. Attempted to test the 6 coils packs in driveway with a new peak voltage meter that I purchased on amazon (sierra brand i think). all the voltages at the 6 coils apppear to be high on this tester compared to the manual. dont know if I can trust this tester or not. checked CDI output and it seems low compared to the readings in the manual, but again dont know if I can trust this meter. 8. gave up and took boat to local well reccommended marine dealer here in Dallas. They said it needed new low pressure fuel pumps and said the diaphrams were bad and cracked. I had them replace the 3 low pressure fuel pumps, picked up boat today and went to the lake, no help still cuts out!!!! What else should I be doing to get this engine to run correctly? I am about to try dynamite!!!! Help!!!

[hvtexskeeter]

I forgot to mention, I also was able to test the throttle position sensor and it seems to test ok, It is set at about .4 volts. Was reading it wrong originally was reading it from the lower side of the plug at wrong wire color per the manual.

[DLAB]

Check your main ignition harness. I had a similar problem once and it was simply a loose connection. Unplug it, put some electrical grease on it, then wrap it with electrical tape after you plug it back in to ensure a good connection. Worth a try

[hvtexskeeter]

the connections at the bottom of the cdi unit on the back of the engine or?

[DLAB]

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[hvtexskeeter]

Checked it today, it was tight. took it apart looked spotless. put it back together and ran boat in the driveway again. Still running like $$$$AA. Bought a new primer bulb just for the heck of and installed it. Still runs like crap. One thing that I did notice is that when running the engine the primer bulb did not remain hard and also noticed the clear fuel strainer on side of engine had air in the top of strainer bowl. Is this normal?

[DLAB]

Man you pretty much covered everything! You rarely hear about an ecu issue with these motors, but it's sounding like that maybe your problem. I have a spare good ecu for a 225 vmax you are more than welcome to try.

[hvtexskeeter]

DLAB thank you very much for the offer! its not often in this world today that someone would loan a part to a complete stranger. I am going to try a new O2 sensor and see if this helps. If that doesnt I may have to take you up on that offer. Thanks everyone for the help on this!

[5bites]

Awesome gesture DLAB.

[HaulinBass]

Clean all the carbon out from where the barbell is between the exhaust passage and the O2 sensor. As stated you've covered everything except the injectors. The three LP fuel pumps are notorious evil triplets even when new.

[hvtexskeeter]

I checked the barbell between the exhaust passage and 02 sensor and also made sure the hole going into the #1 cylinder was clear last week. LP pumps were replaced last week as well but the engine has been ran a few times and is running very bad so the diaphrams on the new pumps may be ruptured again. I will test the ignition system tommorrow am. And I agree I am running out of things to check/change and the next step will be the injectors. they are either gonna be sent to hydrotec for testing or I will take the whole boat there next week. I wish there was a way to test the ecu. The only way I can tell if the ecu is working correctly is that the fuel pressure remains at 36psi while the engine is running and I guess the ecu is what advances the spark timing at higher rpms. Anyone got any ecu checks that I can be done?

[hooken203]

Check all the ground wires around the engine there are several make sure they are tight. Make sure all power connections in the fuse box and that area are tight.

[BassManGuy]

Sounds very familar to a grimlin I chased for a whole year. Check your head gaskets. I did everything you did, and had same problem. I was getting weird voltages as well just like you. It was one of my head gaskets being blown. Worth a check.

[HaulinBass]

Weren't you able to see carbon/detonation on the heads where the gasket was blown?

[GUTTS]

Take and bypass the water separator mine did the same thing. After I id that run great.

[HaulinBass]

Water separator? Referring to the clear VST filter?

[GUTTS]

yes

[HaulinBass]

Interesting. I take it you've got the 40micron in line filter?

[hvtexskeeter]

I bypassed the water separator, no help. Took it to Hydrotec and had Matt work on it for 2 days. Tried several different things including removing the heads, replacing the gaskets, cutting the rev limiter wire. Still not runnin correctly today. They did find one injector that was a little clogged. Runs as good as it has since the onset of the probem, but still cutting out. Gonna try posting a video.

[hvtexskeeter]

I bypassed the water separator, no help. Took it to Hydrotec and had Matt work on it for 2 days. Tried several different things including removing the heads, replacing the gaskets, cutting the rev limiter wire. Still not runnin correctly today. They did find one injector that was a little clogged. Runs as good as it has since the onset of the probem, but still cutting out. Gonna try posting a video.