2002 OX66 200HP Hard Start When Warm

[Poundpuppy727]

I've got a 2002 OX66 200hp that I have about 300hrs on and hasn't given me a single problem until now and man is it a doozy.

A few weeks ago I came back to the house, put my Mako on the lift and when I started to lift realized it wasn't far enough forward so I went to fire the motor up to power forward and it wouldn't start. I was in a hurry so I didn't mess with it until a few days later. At that point I figured what the heck, let me see if it will start and it did instantly without any issue. I thought maybe the problem only existed when the engine was warm so I ran it at idle for a while and then in gear on the lift at low rpms(10-1500) to warm it up. After about 15-20 min of this I shut it off since I hadn't had any issues yet. Tried to restart it and of course it wouldn't.

I quickly figured out how to start the motor(neutral>throttle up half way to WOT>turn key>feather throttle up>motor starts>feather throttle down>let idle) once is fires up it smokes like crazy for a minute or so or until you rev the heck out of it and it will clear out but will not idle smoothly until then but once you do it will run for a while left alone. Either way i start it she goes without a hitch, only issue is starting her.

So far (in no particular order) I have taken apart the O2 sensor and short of bead blasting it I cleaned it up like new and all carbon is gone, also disconnected it to see if the default mode would show it was bad. I have replaced the two low pressure fuel pumps. Made sure that the primer bulb is working. Drained and checked fuel water separator. Disconnected the throttle position sensor to test it out and hope that default mode would prove that was the issue (noticed a difference but problem still persists). Replaced the VST filter, tested fuel pressure (steady 35psi). New spark plugs and also pulled the wires while running to see if maybe I was missing spark in some cylinders.

All of this and I still cannot figure out with is wrong with it. The next steps I was thinking about taking was to replace my rectifier/regulator with my buddies along with my stator to see if either of those are my issue. I am seriously ready to drive this thing out to our spearfishing spot and sink it. I suppose I would have to insure it first, minor details. I am seriously at my wits end with this, granted it is the first and only issue I have had with this motor in the year that I have had it but still.

Any help would be appreciated and welcomed!!!

[cpostis]

I've got a 2002 OX66 200hp that I have about 300hrs on and hasn't given me a single problem until now and man is it a doozy.

A few weeks ago I came back to the house, put my Mako on the lift and when I started to lift realized it wasn't far enough forward so I went to fire the motor up to power forward and it wouldn't start. I was in a hurry so I didn't mess with it until a few days later. At that point I figured what the heck, let me see if it will start and it did instantly without any issue. I thought maybe the problem only existed when the engine was warm so I ran it at idle for a while and then in gear on the lift at low rpms(10-1500) to warm it up. After about 15-20 min of this I shut it off since I hadn't had any issues yet. Tried to restart it and of course it wouldn't.

I quickly figured out how to start the motor(neutral>throttle up half way to WOT>turn key>feather throttle up>motor starts>feather throttle down>let idle) once is fires up it smokes like crazy for a minute or so or until you rev the heck out of it and it will clear out but will not idle smoothly until then but once you do it will run for a while left alone. Either way i start it she goes without a hitch, only issue is starting her.

So far (in no particular order) I have taken apart the O2 sensor and short of bead blasting it I cleaned it up like new and all carbon is gone, also disconnected it to see if the default mode would show it was bad. I have replaced the two low pressure fuel pumps. Made sure that the primer bulb is working. Drained and checked fuel water separator. Disconnected the throttle position sensor to test it out and hope that default mode would prove that was the issue (noticed a difference but problem still persists). Replaced the VST filter, tested fuel pressure (steady 35psi). New spark plugs and also pulled the wires while running to see if maybe I was missing spark in some cylinders.

All of this and I still cannot figure out with is wrong with it. The next steps I was thinking about taking was to replace my rectifier/regulator with my buddies along with my stator to see if either of those are my issue. I am seriously ready to drive this thing out to our spearfishing spot and sink it. I suppose I would have to insure it first, minor details. I am seriously at my wits end with this, granted it is the first and only issue I have had with this motor in the year that I have had it but still.

Any help would be appreciated and welcomed!!!

Suggestion...
You may wish to invest in "Winky Blinky" test harness. This along with a Yamaha service manual that includes the diagnostic codes for your engine may help diagnose your problem. Follow the manual.
Here's a link.
DIAGNOSTIC INDICATOR SET YB-06795

[99yam40]

from what you have said about opening throttle tells me there is an overly rich condition happening at warn start. maybe Rod or someone else can give info on what could cause this on that motor.

[Poundpuppy727]

from what you have said about opening throttle tells me there is an overly rich condition happening at warn start. maybe Rod or someone else can give info on what could cause this on that motor.

Who is Rod and how do I get ahold of him?

I spoke with a buddy today and we talked about it being a leaky injector. I found a place that will clean/rebuild/test and put back to spec for $20 an injector, $128.39 after tax for all 6. Is that a good price? And also is this something that sounds like it could fix my issue? Or are we barking up the wrong tree?

[pstephens46]

Who is Rod and how do I get ahold of him?

I spoke with a buddy today and we talked about it being a leaky injector. I found a place that will clean/rebuild/test and put back to spec for $20 an injector, $128.39 after tax for all 6. Is that a good price? And also is this something that sounds like it could fix my issue? Or are we barking up the wrong tree?

No. Wait for Rodbolt.

Paging Mr Rodbolt!!!! Where is he lately?

[boscoe99]

How long does the fuel pressure hold steady after the key has been turned to the ON position and then to the OFF position without starting the motor? If pressure decays quickly that is an indication of a leaking injector(s). On a fourteeen year old motor it may be long past time to have them cleaned. $20 an injector is reasonable.

http://www.brucatofis.com

[rodbolt17]

look at the spark plugs.
if it is rich they will show it.

if the pressure regulator filter gets clogged it spikes rail pressure,makes it rich.

if a fuel pump leaks it gets rich.
if the VST needle leaks it gets rich.

none of this is monitored by the ECU.

it is a stupidly simple closed loop speed density EFI system.

[Poundpuppy727]

How long does the fuel pressure hold steady after the key has been turned to the ON position and then to the OFF position without starting the motor? If pressure decays quickly that is an indication of a leaking injector(s). On a fourteeen year old motor it may be long past time to have them cleaned. $20 an injector is reasonable.

BrucatoFIS, Inc.

The motor was torn down and rebuilt last july, since I have put 300+ hours on it. I bought it from a well known rebuilder in the area. The guy stands behind his product as well, within the first week computer fried and he ate that, three months later a bear let go in the lower unit and blew it out and he ate that as well. I would assume that the injectors were either replaced or cleaned at that point.

[Poundpuppy727]

look at the spark plugs.
if it is rich they will show it.

if the pressure regulator filter gets clogged it spikes rail pressure,makes it rich.

if a fuel pump leaks it gets rich.
if the VST needle leaks it gets rich.

none of this is monitored by the ECU.

it is a stupidly simple closed loop speed density EFI system.

Where exactly is the pressure regulator?
The LP fuel pumps are brand new.
How do I check the VST needle?

[rodbolt17]

regulator is located on the VST.

to check the needle pull the VST vent line from the intake.
no fuel should leak from the vent line.

one crankcase backfire can destroy a new lift pump.

assume nothing

[Poundpuppy727]

regulator is located on the VST.

to check the needle pull the VST vent line from the intake.
no fuel should leak from the vent line.

one crankcase backfire can destroy a new lift pump.

assume nothing

You say to pull the vent line, I assume you mean while it is running? I'm sure you're thinking that is a dumb question but I want to make sure I'm clear on directions.

I have no issue taking things to a mechanic to have them do the work but I would rather figure it out for myself even if that means getting a little helpful knowledge from others. I'm pretty good with my hands and figuring things out on my own but I am not very familiar with this motor just yet, now my old Merc Tower of Power I could tell you how to do just about anything on. Plus I also enjoy hands on work like this.