Yamaha 200 EFI OX66 VMAX Help please

jetrink52

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Aug 3, 2010
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10
Engine is a 2001 200HP OX66 VMAX. Unload and take off after short idle out of marina to a top speed of 60mph and around 4800rpm.Then a short 5-10 minute sit or fish and take off again it runs perfect. 70mph at 5400-5600rpm. After something gets hot or warm it runs good after a shutdown. It is not the plugs. I was thinking maybe a spark-plug wire or a coil. Any ideas? The engine has run great for years until now. It doesn't miss when acting up........just slow.
The fuel pump diaphrams have been changed, all fuel filters and water separator/filter added. I have always used ring free and new plugs. The thread of posts can be read at Texas Fishing Forum/Boats and Motors.
Steve of Amistad Tackle sent me here. Any ideas I would really appreciate. Thanks.
 

rodbolt

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Sep 1, 2003
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20,066
Re: Yamaha 200 EFI OX66 VMAX Help please

check the fuel rail pressure.
test O2 sensor output voltage.
try to run it with a diagnostic test lamp installed.
with the lamp installed automatic oil transfer is inhibited but all alarms and manual transfers work.
 

jetrink52

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Re: Yamaha 200 EFI OX66 VMAX Help please

Thanks Rodbolt. I may have to look for another technitian around my area as plugs and filters nearly overmatch me but not quite. The things you mentioned I am not familar with. I took it to a Yamaha "master tech" at a dealer twice, left 850 and still runs the same. I have been a year on it. Still fishes ok but it always ran so good I hate to give up on it. The thing is, around here if I can't tell them what's wrong with it, it may not get fixed. I'm not blaming anyone. Passed that. Just want to try and get it fixed. I wrote down what you said so I can have an idea if I find another technitian. Thanks for your help.
 

rodbolt

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Re: Yamaha 200 EFI OX66 VMAX Help please

sometimes it takes a pissed off tech.
many times I have eaten the time but solved the issue.
it defines techs from monkeys.
nice thing about it, it always makes me more knowledge.
 

jetrink52

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Re: Yamaha 200 EFI OX66 VMAX Help please

Absolutely. "Want too" is a big deal no matter what the objective. You have me at a better starting point. Fuel pressure or o2 sensor ought to get it. I appreciate it Rodbolt.
 

rodbolt

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Re: Yamaha 200 EFI OX66 VMAX Help please

the electronics are solid on that engine,failure is rare.
TPS voltage can be monitored,O2 sensor voltage can be monitored,rail pressure can be monitored,lift pump intake vacum can be moitored,can be done with the yamaha flow testing tool or on the lake with a vacum gauge.
if done on the lake do rail pressure and lift pump vacum at the same time.
the injector filters can be removed and cleaned or replaced.
yamaha doesnt offer them but the 7.4 mercruiser MPI about 1999 does.
 

jetrink52

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Joined
Aug 3, 2010
Messages
10
Re: Yamaha 200 EFI OX66 VMAX Help please

Rodbolt. If I have the o2 sensor replaced would that have a better than average chance of fixing the issue? Thanks again.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Yamaha 200 EFI OX66 VMAX Help please

nope
but it would have a better than average chance at spending about 370 for a sensor and an hour or so labor.
do you own a multimeter,digital one?
 

jetrink52

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Joined
Aug 3, 2010
Messages
10
Re: Yamaha 200 EFI OX66 VMAX Help please

I have what I think is a multimeter but it isn't digital. It is made by Actron.
If you can lead me to a fix I'll make it right. Like I said.......I have been a while on this problem. It does it every time day after day. Start of the day it is like no footfeed left above 4800. Stop after the warm-up for 10 minutes, take off again and it runs like a striped ape the rest of the day.
 

greggeorge

Recruit
Joined
Aug 16, 2010
Messages
1
Re: Yamaha 200 EFI OX66 VMAX Help please

Engine is a 2001 200HP OX66 VMAX. Unload and take off after short idle out of marina to a top speed of 60mph and around 4800rpm.Then a short 5-10 minute sit or fish and take off again it runs perfect. 70mph at 5400-5600rpm. After something gets hot or warm it runs good after a shutdown. It is not the plugs. I was thinking maybe a spark-plug wire or a coil. Any ideas? The engine has run great for years until now. It doesn't miss when acting up........just slow.
The fuel pump diaphrams have been changed, all fuel filters and water separator/filter added. I have always used ring free and new plugs. The thread of posts can be read at Texas Fishing Forum/Boats and Motors.
Steve of Amistad Tackle sent me here. Any ideas I would really appreciate. Thanks.

I had the same problem. Turned out to be the anti-knock sensor, it would send a signal to the computer and not allow the engine to go over 5000 rpm. Easy to change. screwed into the right cyl head and had only 1 wire. If you disconnect it you will get the same sympton all the time (will never go over 5000 rpm) Good Luck!:)
 

rodbolt

Supreme Mariner
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Sep 1, 2003
Messages
20,066
Re: Yamaha 200 EFI OX66 VMAX Help please

dissconnect it and you also get an 1100 RPM idle, all the time.
why not use the diagnostic test lamp. if the knock sensor throws a code it will show it.
 
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