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Old 04-09-2012
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Default 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm-HELP

New to forum so sorry if this is been addressed in past. I need advice.

I have a 2003 Yamaha 200 HP OX66 EFI (VX200B) that has never given me a problem. I bought it new. Has had 100 hr checkup every spring since new at reputable dealer. Very well maintained, has 527 hours. Last spring (2011), I started having slight hard start rough idle after running to fishing spot and turning off engine for 10-45 minutes. This would continue all day on a trip but didn't seem too bad as the issue was minor and would clear up within 5-10 seconds after starting. Engine would then be perfect....idle great, run great, up to 6000 rpm's, just like new. Come off to idle at next spot and idle 700-800 rpm, just perfect until I turned engine off and sat for some period of time, then slight hard start again, but quick clear up. Cold start is great, with no problems, good idle. Used it all last year and was just a minor irritant. Put about 75 hours on engine since it started doing this. In January/February this year, it seemed like this problem seemed to get a little worse....still cleared up quick after warm start, but sometimes had to advance throttle to get started, and engine would idle rougher and smoke quite a bit for first 10 seconds after hard start. Would idle at 300-400 rpms while rough idle until it cleared up and idled fine at 700-800 rpms within 10 or so seconds. Still, after it cleared up, all great....good idle and runs great at all speeds. If I stopped and tried restarting immediately, start and idle was great. Only after engine was off for a while did I have a hard start.

So....I took it to the dealer/shop 2 weeks ago for yearly 100 hr maintenance and asked for them to also fix this problem. They have replaced all filters (water sep, filter on side of engine), spark plugs, cleaned O2 sensor, etc. Lake tested and duplicated hard start problem. They checked compression (said it was perfect), checked fuel pressure (36 psi while running and 28 psi and holding after turning off engine), checked all electrical components and couldn't find anything. Scratched their heads and mentioned vapor lock and finally pulled a hose on top of Vapor Separator and found fuel coming out. Opened up VST and found needle valve worn out. They were convinced that was the problem. Replaced needle valve and cleaned out VST and lake tested. Guess what....warm hard start was still a problem. They called Yamaha and Yamaha said it was "winter fuel mix"!?!?. Impossible as I have run at least 15 tanks of gas since last spring. Current gas was put in within last month, so it is running on fresh fuel. Dealer is stumped. Bought boat from this dealer, know the owner, and the same tech has worked on this motor since I bought the boat in 2003, so I have some confidence in them. They are not ready to give up, but I took boat from shop last week and ran it to see if it is any better. I put in double dose of Ring Free and ran it all day on Friday. Ran thru about 25 gallons of gas and the problem still exists, just like before. Engine is perfect except hard start rough idle when warm. No change from all of the past 12 months.

So....HELP...what could I be missing? Still hard start, rough idle and lots of smoke when first started warm until it clears up in 10 or so seconds (Quicker if I advance throttle). I think I am too “rich” (flooding) at start. Could I be getting gas leaking into manifold or cylinders after I turn engine off? Could this be a primer bulb issue (this is original bulb). I have never had to pump it since I have owned the boat. Motor always started within 1-2 seconds without ever pumping it even after sitting a month. Checked bulb throughout day on Friday and it never seemed to get really hard when pumped. Actually, I pumped it a bunch before one start, and it seemed to make the start even harder. Or, could I have a pin hole in one of my fuel pump bladders? Remember...dealer said my pressure held at 28 psi after turning the engine off. Not sure how long they waited. What else could it be? I like things right, so it's hard for me to just accept that I will have to live with this. Remember....if I wait a week and walk up to my engine and turn the key...it starts great immediately with good idle rpms. Seems like if the gas in dumping, then it has time to evaporate over time and give me a good cold start.


You can tell I am frustrated....appreciate any incite on this. Sorry for the long verbiage, but wanted to get complete info to everyone so as to get the best most accurate response.
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Old 04-09-2012
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Has the dealer gotten any codes from the winky blinky?? Man it sure is looking like a fuel problem, assuming they checked the low pressure fuel pumps?
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Old 04-09-2012
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No mention of codes from dealer/shop. But I talked to both the owner and tech (owner has 3 stores and he has been in business a long time). Owner said tech has never encountered a problem he couldn't figure out. Tech was not happy he couldn't fix. Two lake runs and lots of time he spent on it. We all brainstormed. He thinks it is a fuel problem also. Just told me about the fuel pressure test I mentioned in post. If the pressure is holding how would you test the 3 fuel pumps? Do you just replace them? If one is bad, could it flood gas into motor?
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Old 04-09-2012
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Believe you have 2-pumps. To test the LP pumps they need to be unbolted from the block but still connected. Pump the primer bulb and look for fuel leaking from the back of the pumps. That's the only indication that a diaphram is bad. Keep posting, like to see the outcome of this. Looks like a real beaut...
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Old 04-09-2012
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Re-read the post and it sure looks like LP pumps to me. The give away is the primer bulb never got hard. This should get hard after the VST is fuel of gas. Did you notice a fuel sheen on the water when idling?
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Old 04-09-2012
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Thanks, I can check those....I checked some online schematics and thought there were 3, but one may have just been an exploded view. Don't they only cost about $45 each? Since they are original and about 9 years old, should I just replace them anyway? So is it possible they could flood a warm motor while not running if a diaphram is leaking? If so, then this would be a good possibility. Thanks!
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Old 04-09-2012
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Thanks for taking the time to re-read the post. I know it was long, but more complete information can make a big difference. I did "not" notice a fuel sheen on the water, but was not really looking. But have never smelled a gas smell. But does "feel" like too much fuel.
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Old 04-09-2012
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$45 is about right. Can get them here on boats.net. Be sure to get new gaskets, they're not included with the pump and don't torque the bolts too tight, they have plastic bodies. This is just a stab at the problem. I'm no tech, just read alot and have 2 of these OX66's.
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Old 04-09-2012
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injector stuck open ?
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Old 04-09-2012
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motor is great at idle through full throttle 99% of time. only hard start for about 10 seconds then everything great. wouldn't an injector stuck open cause other problems?
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Old 04-09-2012
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in reading your key on/off results.... shouldnt pressure hold @ 36.. when key turned off?...drop off slower?
its been a bit for me having pressure issues but it sounds like fuel is dumping when it sits...
as i was told by a tech friend there is an oring on top of hp pump that can let pressure bypass/drop, where to im not sure, recirc possibly

Last edited by jb123; 04-09-2012 at 08:20 PM.
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Old 04-09-2012
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Thanks JB123....I didn't know enough to ask about the drop from 36 to 28 when key turned off....but he said it held at 28 psi, so I assumed that meant that injectors were holding. I will have to clarify. As for o-ring, i will have to explore.
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Old 04-10-2012
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lots of o-rings around HP pump? any idea?
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Old 04-10-2012
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#24 or 31 but you should ask your tech as well
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Old 04-13-2012
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any good news ??
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