2000 Yamaha OX66 Problems...

[Skin]

Guys,

New to the forum and I have not searched in great detail, but I'm looking for some help. I have a 26' Glacier Bay with twin 2000 150HP OX66's on the back. After sitting up, the port motor ran very poorly at idle and would die after running at 1500 or so RPMS and be very hard to start or would not restart unless I wait for several minutes. I replaced the engine based water separator filter, the onboard Sierra fuel/water separator filter and the plugs. After doing that work, I started the boat and it seemed to run fine, but then back to the same thing again. (Note: After replacing the filters, the engine based filter took quite a while to fill with gas.) I would start to rev the engine and it would run for a minute or less at higher RPMs and it would die. I checked the plugs and they were dirty, so I cleaned them up and also replaced replaced the low pressure fuel pumps, at another's suggestion.

I am still experiencing the same problems. My dad seems to think it's a fuel starvation problem. Any thoughts before I tear into the VST and pull the O2 sensor.

Thanks for your help.

Loren

 

[mpsyamaha]

Re: 2000 Yamaha OX66 Problems...

my next thoughts are the same as yours.... check out the VST and the o2 sensor

 

[snowmon]

Re: 2000 Yamaha OX66 Problems...

may be a restriction between tank and engine. is primer bulb full or collapsed? are you doing scheduled maintenance? if not could be one or several issues. need more info

 

[rodbolt]

Re: 2000 Yamaha OX66 Problems...

my thought would be to research what the VST is and why its there as well as what the O2 sensor is and why its there.
but yes check the needle valve in the VST as well as the pump filter, when you remove and clean the O2 sensor is rather pointless unless you test the sensor output voltage when your done as per the 3 tech bullitens that are out.
a note from the manual, running above 4000 RPM with the sensor dissconected(IE bad) will cause the engine to run lean, DO NOT run above 4000.
all the O2 sensor maint in the world is useless unless the output voltage is tested as per the tech bullitens.
the Ox66 is a very simple EFI.

 

[TomS]

Re: 2000 Yamaha OX66 Problems...

Rodbolt,

What are some things to look for when inspecting the VST needle valve? Do you just want to make sure it can move freely, or are their signs that it needs to be replaced, etc?

Thanks!

-- Tom

 

[Skin]

Re: 2000 Yamaha OX66 Problems...

Thanks for the comments.

Yes, scheduled maintenance has been performed and the primer bulb is full and not collapsed.

 

[rodbolt]

Re: 2000 Yamaha OX66 Problems...

folks its a needle valve, its not a magic device. you inspect the tip for grooving/deformation and the seat for the same.
if its leaking it will cause a rich running condition cause it vents to the intake.
but testing fuel rail pressure, cleaning the VST pump screen and the little known pressure regulator screen as well as cleaning the injector screens is all simple routine maint, do it or post about detonated piston crowns.
same as replacing the lift pumps about every 3 years, do it or you may get to post about the rod that came out the block.

 

[TomS]

Re: 2000 Yamaha OX66 Problems...

Thanks Rodbolt, I know it ain't magic, but if you've never seen one before its kind of hard to know what to look for to tell if its broken

I've been following all your advice on maintenance the last couple of years, and gradually becoming more comfortable handling the more complex stuff.

I've done the t-stats, fuel filters, oil pump filter, low pressure pumps, replaced the spark plug caps, cleaned the pressure control valve, change the lower unit oil and so on.

I also clean the VST filter and O2 sensor, check the winky blinky, replace the f/w separator filter, check the fuel rail pressure, adjust the TPS and check the oil control rod every 100 hours, etc..

This will be the first time that I go in and inspect the needle valve, also plan on pulling the fuel rail to inspect/clean the fuel injector filters and plan on replacing the pressure regulator screen.

This is the first engine of any kind that I've ever worked on, and I wouldn't be able to do any of it without the information you post here, so please know that it is really appreciated!

-- Tom

 

[rodbolt]

Re: 2000 Yamaha OX66 Problems...

no worries.
its all fairly simple just takes time.
do you have the tech bullitins on testing the O2 sensor output voltage, its imperative.
disregaurd the flame test for it, its a teat on a boar hog.
if nothing else turns up you may have to test the recirc check valves located on the engine block. they dont give much problem but can.

 

[ghind]

Re: 2000 Yamaha OX66 Problems...

Hi Rodbolt

Any suggestions to where I can get the three tech bulletins from?

Thanks

 

[rodbolt]

Re: 2000 Yamaha OX66 Problems...

you can get them at the same dealership your gonna buy the gaskets and such from to do the maint.
they are on part smart,YDS and in various marine tech guides.