2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Joined
Apr 9, 2012
Messages
8
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....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.
 

99yam40

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Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Did replacing the needle and seat in VST solve the problem stated here "pulled a hose on top of Vapor Separator and found fuel coming out" or has anyone looked again to see if it is still coming out top of VST
 
Joined
Apr 9, 2012
Messages
8
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Yes, tech found gas coming out top of VS, opened it up, found worn needle valve, honed seat (can't be replaced), replaced needle valve, lake tested, warm hard start still existed and he check VS (pulled hose off top) to make sure gas was not still leaking out top of VS. It was not, so that problem was fixed, but hard start was not. Perplexing....
 
Joined
Apr 9, 2012
Messages
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Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

99....thanks for giving this some thought. Yamaha techs are perplexed....I'm perplexed. Gotta be a simply problem. I quized them quite a bit, and they seemed to have check everything. As I said, motor is great at idle all the way to full throttle except for first 10-15 seconds at warm start.
 

99yam40

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Joined
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8,882
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Seems like I remember reading about a vapor problem from VST overheating dumping too much vapor into intake, but cannot remember what motors. Water Cooler bolted to VST maybe and making sure you idled for a couple of minutes after running at speed to help motor cool off before shutting down. Any way some thing to look for
 

C G Smith

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Joined
Apr 16, 2012
Messages
4
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Have you figured out the problem? I have that same issue with a 2003 (ox66), im trying to figure it out. Mine started in October last year.
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....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.[/QUOTE]
 
Joined
Apr 9, 2012
Messages
8
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

No I have not. Haven't had time to get back to my bayhouse in Rockport to work on it. I am convinced that fuel must be dumping somewhere after I turn it off when warm. After it sits for a day or week, the fuel evaporates and it starts fine. I think I will start with checking the LP fuel pumps. I have been told that a pin hole in one of the bladders could cause this. I think I will unbolt them, but leave the fuel lines connected and then pump the primer bulb and see if any fuel is leaking. I may just replace them since they are original.

The crazy thing is that this seems to be a really common problem that people post about often, and nobody seems to have a common solution or trouble shooting plan. I'm really surprised that my yamaha techs were also stumped. I will be able to work on this early next week and report back.......
 

C G Smith

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Joined
Apr 16, 2012
Messages
4
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Thanks Please keep me informed. After a couple hours search on the net, I think the problem may be one of the low pressure fuel pumps or all three. I have also read somewhere that you can remove them from the block and pump the primer bulb to see if they leak. I am going to try this. What surprises me is your dealer does not know about the test. Is this a good way to test LP fuel pumps? I asked a mechanic on the telephone about the LP fuel pumps. He ask me if I ever needed to pump the primer bulb to start engine, and I replied no, I can let the boat sit for months and never use the primer bulb and the motor will start before the motor turns over twice. I only have this problem after the motor has been run and then sits for a little while. He seemed to think after that answer that this must not be my problem. This seems to contradict what I have been reading online.
 
Joined
Apr 9, 2012
Messages
8
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

You and I have the exact same problem. In 9 years, I have never had to pump my primer bulb. Motor starts immediately when cold....even after sitting for a month. I am going to give the LP fuel pumps a test. Sure hope that is the problem. I am concerned that your mechanic doesn't feel this is the problem. But I will report back next week. You do the same.
 
Joined
Apr 9, 2012
Messages
8
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

UPDATE!! Problem solved! Replaced all 3 LP fuel pumps and problem solved. Took the old ones apart to see if I could figure out which one was leaking and one had a bulge on the bladder, but no obvious hole. When I took them off, I looked for a sign of leaking from the hole on the back, but none present. Ran on the bay for 8 hours yesterday (probably 30 warm starts plus used 20 gallons of fuel) and started perfect within a second every time. 800 rpms...perfect. Plus I caught fish!

As a side note, came back to Houston today and stopped by the dealer and talked to the owner and Tech who worked on this problem 2 weeks ago....both said they knew the test procedure and had disconnected the pumps and pumped the primer bulb to test them. No leakage was noted so they moved to the next possible cause. They figure the hole must have been small. Known them (and trust them) since I bought the boat from them 9 years ago. Owner will give me $100 credit on next repair, and was very sorry they didn't fix it when it was in.

Smith....let me know if this fixed your problem also.
 

C G Smith

Recruit
Joined
Apr 16, 2012
Messages
4
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Update. My problem solved as well. Replaced all three lp fuel pumps and fished a tournament today. Motor cranked like new, even when hot, no more hard starts or rough idle when warm. Pretty easy fix. Thanks for keeping me updated on your problem it helped solve mine.
 

99yam40

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Sep 7, 2008
Messages
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Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

It would be best to do the maintenance the Yamaha recommends, probably will keep from having issues
 

Crusher23

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Joined
Jul 13, 2010
Messages
5
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

hey guys,
I have the same issue with my 2001 225 VMax. How do i find the right part(s) for my motor?
Mine started doing this last summer and I haven't been able to figure it out.

Thanks
Steve
 

C G Smith

Recruit
Joined
Apr 16, 2012
Messages
4
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

boats. net has the low pressure fuel pumps we have been discussing. Part number 6E5-24410-10-00 for your motor. They have a schematic on the web site so you can double check my part number. They cost $37.50 each.
 

DNR65

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Joined
Jun 24, 2012
Messages
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Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Nicely done! I too have been experiencing this problem just this year with a 200hp 2000 ox66 and had a few suggestions from my trusted mechanic as to what the issue might be and nothing seemed to provide a real lead or resolution! I too will then replace the lp fuel pumps and cross my fingers that this resolves the issue.

I have been reading these threads for some years now and have just joined the this very informative forum!
 

dunnitagain

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Joined
Apr 4, 2010
Messages
8
Re: 2003 Yamaha VX200 (OX66) Hard Start Rough Idle when warm

Sorry to revive an old thread but I thought some input might help. Its not the hole in the LP pumps leaking fuel out. But rather letting air in, this in turn aerates the fuel going into the VST. Causing an excessively rich oil mix. On hot start it seems like a fuel rich problem ,but instead a OIL RICH problem
 
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