Yamaha OX66 200hp EFI...HELP!!!!! Bogging down. - SaltwaterCentral.Com

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autovalue
Posts: 57
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Wed Jul 20, 2016 9:16 pm
Guys I need a little help here...got a yamaha ox66 200hp EFI with low hours...less than 500. Never had an issue at all until this past weekend. In the past, I had been offshore running wide open and RPMS would drop say 200-500 rpms every so often...took it in, got it serviced...changed fuel filters (not the VST filters thought!!) but it fixed this problem in the past. Well NOW, what I have going on is completely different...motor runs perfect, idles perfect, doesnt lack power, get on plane easily...has always been rough on fuel and oil but that is pretty common...burns a tank of oil for every tank of fuel...2 or 3 gallon oil reservoir...~120 gallon fuel tank. I am told this is a good ratio. So it doesnt really matter what RPMS I am running...I could be running 5000rpm or 3500rpm and the motor will completely BOG DOWN TO IDLE...doesnt cut off! Just bogs down completely but again, it doesnt run rough ones it bogs down...it idles like a sewing machine. I might run for 5 miles or more at 5k rpm and then it may do it...I might run for 1/4 mile and it may do it...It is very very random. I obviously dont want to get stuck offshore! I have read up and tons of people have had the issues that I previously had BUT I havent seen any forums and such with the EXACT issues I am having. PLEASE HELP! Any info is greatly appreciated. I am heading down this weekend to try and work on it a bit so and advice would be awesome.

Thanks,

Will
  
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Capt_Rich
Posts: 83
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Wed Jul 20, 2016 9:38 pm
The sending unit for my fuel flow meter caused this same issue for me. I disconnected it and problem solved. ETHANOL IS NOT YOUR FRIEND.It ate the insides up causing the blockage.  
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glacierbaze
Posts: 773
Location: Chapel Hill/Pine Knoll Shores, NC
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Thu Jul 21, 2016 1:10 am
Mine is doing something similar, but it only bogs at high RPM, and picks up immediately if you back off. My mechanic gave me good advice, which I will try this week-end.
Hook a portable 6 gallon tank directly to the motor, make sure you vent the cap. If it bogs, it's in the motor, carbs, fuel pump, etc.
If it runs strong, it's in the boat, tank, fuel lines, pick ups, etc.
  
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rockhound
Posts: 969
Location: wilmington
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Thu Jul 21, 2016 2:28 am
Could be low pressure fuel pump.Not supplying enough fuel to vst on too end.  
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autovalue
Posts: 57
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Thu Jul 21, 2016 3:02 am
capt.rich...you wouldn't by chance know where it is on my 200 ox66 efi would you or perhaps have a description of what I should be looking for. and I know what you mean...ethanol sucks! The only thing is I cant remember the last time I fueled up anywhere other than the marina which has ethanol free supposedly.

glacierbaze...yours sounds like the more common issues...probably a fuel filter needs changing. If I am not mistaken there is one or 2 filters that can be changed easily and then there is the VST. As I said, last time mine did what yours is doing, I changed the ones I could see and get to myself without too much knowledge and the problem went away.

rockhound...I am told there are 3 pumps...is this true?
  
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Haynick
Posts: 98
Location: Bogue Inlet
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Thu Jul 21, 2016 10:11 am
Mine did the same thing, sometimes if you turned it off and restarted it the problem would go away, after months of issues, sometime it wouldn't do it at all...Turned out to be the VST Tank needed cleaning, & filters and the high pressure fuel pump had a bad diaphragm. I have been trouble free for (6) 120+ mile trips. I also run ring free every time I fill her up.
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rockhound
Posts: 969
Location: wilmington
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Thu Jul 21, 2016 12:15 pm
2 low on block and 1 high in vst.prob 1 of them,lows are cheap and easy to replace,clean and check vst as well.also if you have help you can check the pressure out of the vst with gauge.  
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David20675
Posts: 464
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Thu Jul 21, 2016 5:39 pm
Call me and I will tell you you would not believe it fixed mine 9805811956 $15 part  
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David20675
Posts: 464
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Thu Jul 21, 2016 5:40 pm
Call me and I will tell you you would not believe it fixed mine 9805811956 $15 part any alarms going off ?  
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bluewaterfisher273
Posts: 165
Location: Beaufort, NC
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Fri Jul 22, 2016 2:06 am
When is the last time the O2 sensor was cleaned? When was the last time the draw tube was cleaned where the O2 is mounted? If it's never been checked or serviced...I would also check it.
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walterj
Posts: 9
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Sun Jul 24, 2016 11:40 pm
The next time it bogs down pull the cover off and check the oil level in the reserve tank on the side of the motor. If it drops to a certain level, the computer shuts down high rpms to protect motor. I went through this and ended up changing over and mixing my oil in the tank when i fuel. Good Luck!  
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Fernie
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Thu Jul 28, 2016 12:44 am
O2 sencor  
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4reellife
Posts: 475
Location: emerald isle
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Thu Jul 28, 2016 11:58 am
VST filter
Simple fix
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intubaited
Posts: 195
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Fri Jul 29, 2016 12:56 am
You either need one or both LP fuel pumps and/or your VST filter is dirty. You have 2 LP fuel pumps. They are on the engine block between the engine mounted fuel filter and the VST (aluminum tank with 9 screws around the top of it).

Unbolt the LP fuel pumps from the block (two bolts each) and pump your primer bulb. If they leak fuel, they need to be replaced. They're about $40 each and you should replace them every 3 years or so before they fail.

Unbolt the VST (three 10mm bolts), take the 9 screws out of the top to separate the tank. Dump that fuel into a container and wipe the inside clean. Let the fuel settle in the container for an hour or so just to see what you see.

Attached to the top of that tank (submerged in the fuel of the VST) is the HP fuel pump. The VST filter is on the bottom of it. Rotate it off, it's pretty simple.

Pry the filter apart so the pie wedged disk is just a flat disk. Hold it up at arm's length and look through it at a light. Spray carb cleaner through it until the screen is absolutely clean. It is 2 micron so the screen is very fine. Keep checking against a light so you know when it is clean. You will actually see a grid of 9 lights when it is right. Ask me how I know.

You will need a VST gasket because the old one will have swollen and won't go back in the groove. Keep the old one and once it has dried (maybe takes a week) you can use it next time (they're about $30).

Reassemble and you'll be good to go. wtg
  
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hotrodmarlin
Posts: 17
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Fri Jul 29, 2016 1:37 am
O2 sensor. Simple fix  
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intubaited
Posts: 195
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Fri Jul 29, 2016 1:45 am
O2 sensor doesn't do anything below 1800 rpm or so in an OX66 so it would never die down that far. It is fuel supply.  
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glacierbaze
Posts: 773
Location: Chapel Hill/Pine Knoll Shores, NC
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Tue Aug 02, 2016 5:02 pm
"Unbolt the LP fuel pumps from the block (two bolts each) and pump your primer bulb. If they leak fuel, they need to be replaced. They're about $40 each and you should replace them every 3 years or so before they fail. "

My mech told me that if I tried this test, the two 10mm bolts not only hold the pump to the block, but they also hold the pump together, gaskets, diaphragm, etc.
Before pumping on the bulb, put the bolts back thru with nuts on the back, or put the pump in some sort of clamp to keep it together. The leak will be out the back side of the pump.
  
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rockhound
Posts: 969
Location: wilmington
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Tue Aug 02, 2016 5:23 pm
intubaited wrote:
You either need one or both LP fuel pumps and/or your VST filter is dirty. You have 2 LP fuel pumps. They are on the engine block between the engine mounted fuel filter and the VST (aluminum tank with 9 screws around the top of it).

Unbolt the LP fuel pumps from the block (two bolts each) and pump your primer bulb. If they leak fuel, they need to be replaced. They're about $40 each and you should replace them every 3 years or so before they fail.

Unbolt the VST (three 10mm bolts), take the 9 screws out of the top to separate the tank. Dump that fuel into a container and wipe the inside clean. Let the fuel settle in the container for an hour or so just to see what you see.

Attached to the top of that tank (submerged in the fuel of the VST) is the HP fuel pump. The VST filter is on the bottom of it. Rotate it off, it's pretty simple.

Pry the filter apart so the pie wedged disk is just a flat disk. Hold it up at arm's length and look through it at a light. Spray carb cleaner through it until the screen is absolutely clean. It is 2 micron so the screen is very fine. Keep checking against a light so you know when it is clean. You will actually see a grid of 9 lights when it is right. Ask me how I know.

You will need a VST gasket because the old one will have swollen and won't go back in the groove. Keep the old one and once it has dried (maybe takes a week) you can use it next time (they're about $30).

Reassemble and you'll be good to go. wtg

If you take the gaske tand t in the freezer,Itll work just fine!
  
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intubaited
Posts: 195
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Tue Aug 02, 2016 6:05 pm
glacierbaze wrote:
"Unbolt the LP fuel pumps from the block (two bolts each) and pump your primer bulb. If they leak fuel, they need to be replaced. They're about $40 each and you should replace them every 3 years or so before they fail. "

My mech told me that if I tried this test, the two 10mm bolts not only hold the pump to the block, but they also hold the pump together, gaskets, diaphragm, etc.
Before pumping on the bulb, put the bolts back thru with nuts on the back, or put the pump in some sort of clamp to keep it together. The leak will be out the back side of the pump.


There are phillips head screws that still hold the pump together. Even with those out the pumps can be tough to separate from the internal gasket.
  
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intubaited
Posts: 195
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Tue Aug 02, 2016 6:10 pm
[/quote] If you take the gaske tand t in the freezer,Itll work just fine![/quote]

For some reason that has never worked for me. I just put the used gasket in my parts box for the next time. Not sure exactly how long they're in there before they shrink all the way back down.
  
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glacierbaze
Posts: 773
Location: Chapel Hill/Pine Knoll Shores, NC
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Tue Aug 02, 2016 7:27 pm
intubaited wrote:

There are phillips head screws that still hold the pump together. Even with those out the pumps can be tough to separate from the internal gasket.


Mine is '93 carb 200, not OX66. Are they the same, the pumps that is?
  
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intubaited
Posts: 195
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Tue Aug 02, 2016 7:44 pm
glacierbaze wrote:
intubaited wrote:

There are phillips head screws that still hold the pump together. Even with those out the pumps can be tough to separate from the internal gasket.


Mine is '93 carb 200, not OX66. Are they the same, the pumps that is?


Yep. Two of them. I had a 150 on a bass boat back then and used to change the same exact pump.
  
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rockhound
Posts: 969
Location: wilmington
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Wed Aug 03, 2016 12:32 am
intubaited wrote:
If you take the gaske tand t in the freezer,Itll work just fine![/quote]

For some reason that has never worked for me. I just put the used gasket in my parts box for the next time. Not sure exactly how long they're in there before they shrink all the way back down.[/quote]
Yea,I have to go through the same stuff,I've twin 250 hpdis,I'll also put some grease in the gasket Valley as well,Works like a champ.
  
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hotrodmarlin
Posts: 17
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Wed Aug 03, 2016 2:46 pm
intubaited wrote:
O2 sensor doesn't do anything below 1800 rpm or so in an OX66 so it would never die down that far. It is fuel supply.

I'm no mechanic but I've owned 2 Ox66 motors, both acted exactly as he described. They ran smooth at idle speed and both times it was the O2 sensor.
  
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intubaited
Posts: 195
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Wed Aug 03, 2016 4:07 pm
hotrodmarlin wrote:
intubaited wrote:
O2 sensor doesn't do anything below 1800 rpm or so in an OX66 so it would never die down that far. It is fuel supply.

I'm no mechanic but I've owned 2 Ox66 motors, both acted exactly as he described. They ran smooth at idle speed and both times it was the O2 sensor.


It's a challenge from behind a keyboard. We all see and hear things a little differently so you could be right on target. I'm curious to hear what the outcome will be.
  
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jdupree
Posts: 40
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Wed Aug 03, 2016 4:18 pm
Should be the VST filter. I just replaced my filter and it was dirty. As stated in earlier post, put VST gasket in freezer until ready to put back on. Use vaseline to hold gasket back in place.  
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afterours
Posts: 1
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Wed Aug 03, 2016 5:10 pm
after cleaning VST, fuel filters and changing O2 sensor (all good things to do anyway as they are recommended on a regular service interval), if it does not fix the problem, check voltage to electric fuel pump. lower v = lower fuel flow. the specs for voltage from idle to WOT are readily available on the web. it could be a bad wire or connection somewhere in the circuit.  
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intubaited
Posts: 195
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Wed Aug 03, 2016 6:06 pm
afterours wrote:
after cleaning VST, fuel filters and changing O2 sensor (all good things to do anyway as they are recommended on a regular service interval), if it does not fix the problem, check voltage to electric fuel pump. lower v = lower fuel flow. the specs for voltage from idle to WOT are readily available on the web. it could be a bad wire or connection somewhere in the circuit.


It would be easier to put a fuel pressure gauge on the schrader valve on top of the VST. It should hold around 36 psi.
  
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Yamaha OX66 200hp EFI...HELP!!!!! Bogging down. - SaltwaterCentral.Com

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