1998 OX66225 hesitation/stumble

[slapshotjh]

Hello,

I repowered this season with a used outboard (1998 OX66 225hp) with a zero hour powerhead. Went through the 15 hours of low rpm (varied) use and am now at about 30 hours total. From day one It has idled quite high (1200 rpms) and had a stumble in the range from 1200 rpms up to where the boat starts to climb up on plane. You cannot move the boat at high rpm non-planing speeds - it bogs, coughs and stumbles. Additionally WOT with motor trimmed til it just starts to cavitate is 4500 rpms. Fuel consumption also seems to be higher than I would expect (have a Navman fuel monitor and have checked calibration). 14gph at 27 mph is worse than what I got with the old carbed motor. I also can see raw fuel or oil in the water when I return to the dock. It seems to be coming from the exhaust.

Thus far I have replaced the O2 sensor (the first one fell off, and broke the cross tube during the break-in period), replaced the VST filter and o-ring, ran a Seafoam shock treatment through it. The plugs were new, and don't look bad. the boat previously had a 96 carbed Saltwater Series II that had a host of ethanol issues. I assume that alot of the tank crud has been flushed out already as we have had ethanol in CT now for 3 seasons and the boat was used quite a bit (the Racor 90gph10micron filter has been replaced each season).

I also had a mechanic look at it. In addition to replacing the VST filter, one of the things he did was to pull the low pressure pumps and check them by squeezing the primer bulb. He said they were ok and noted that they looked new.

I will be borrowing a fuel pressure gauge soon to monitor the pressure when the stumble occurs.

The O2 sensor was most likely not reinstalled properly when the powerhead was put back on. Is it possible that the throttle position sensor may be out a wack as well? I assume that would be removed to do a powerhead exchange. Would it need to be tested and adjusted when it was reinstalled?

The dealer that I bought this from has been no help. I have a 90 day warranty, but he says it does not cover fuel or electrical sensor issues. I can't get the boat to him to diagnose as he is in another State (no trailer) but he claims it is probably fuel related (telephone diagnosis).

I have searched the forums, and did not really find a problem like this one. Anybody have any thoughts?

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

ok, 3 main causes of the 1200 RPM idle, a sensor failed,the linkage adjustments are way out or you have a serious airleak in the crankcase.
make sure all the sensors,especially the knock sensor is plugged in.
check the timing at an idle, if its locked at 7*BTDC its definatly set a code.
if the coolant temp sensor is bad it can cause the high idle and rich low speed.
but dont keep shifting at that speed or you may get to find out how expensive a fwd gear and shifter clutch is.
if its done it from day one then why did you accept delivery of it ?

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

Rodbolt - thanks for the suggestions. I now have a plan of attack.

I accepted the motor because it seemed fine in the test tank (no surprise there). In the test tank there was no tach, so no way to notice it idles high. I brought the engine home and installed it myself in my driveway. I thought that the linkages were not adjusted correctly. I've cehcked them again, and have even disconnected the throttle linkage to see how low it idles on its own and it still won't go below 1200.

Your response leads me to a new question - perhaps there is a sensor unplugged. I did the rigging with the help of a friend. The wiring in the boat was for a 1996 carbed Saltwater Series II 200. The new motor is the 1998 OX66 225. I remember hooking up the two main wiring harness plugs. If my memory is correct, there were 2 yellow wires (I cannot remember the color of the stripe on the wires) on the engine harness that plugged into empty sockets on the boat harness. I doubt that would result in an unplugged sensor but maybe?... All gauges and buzzers are working at the helm (tach, speedo, voltage, oil level, etc).

Can I check the timing the same as on a car (timing lite hooked up to number one plug wire)? What should it be set at?

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

it checks just like a car.
however the ECU controls engine timing.
I dont haqve my manuals here but memory says it should be like 5-7* ATDC, if its 7*BTDC you most likly have a sensor issue.
most sensor failures on that motor will lock idle timing at 7*BTDC, some will keep it locked there others will allow WOT.
the only sensor that wont do much is the O2 sensor, if it fails or goes out of range fuel is fixed rich at idle and lean above 4000 RPM.
most of the sensors can be tested with a multimeter.
at 7*BTDC and normal fuel/air you get about 1200 RPM.

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

Rodbolt,

Thanks for your insightful posts. I was able to get down to the boat this morning and run some tests. The timing off no1 is reading roughly 7.5 degrees ATDC.

I have a Clymer manual that covers my engine. Not the best manual, but it does have some of the test procedures.

I adjusted the shift and throttle linkages to spot on - they were a little bit off.

I found the throttle position sensor to be out of spec. It was reading .7 volts, I adjusted it down to 0.505 volts. Ran the engine throttled up and down a couple of times and find that it reads .505 when in neutral now. I may have to recheck this once I get the idle back to where it should be - remember the boat won't idle below 1100 rpms as it is now.

The engine still idles very high. I was unable to test the knock sensor as my DVM does not have AC milliamps. I found that the new oxygen density sensor checks out for heater resistance and output voltage lower limit. (It is brand new).

I was unable to check the crankshaft sensor as my DVM does not read peak voltage - I tried hooking it up to read DC volts and got nothing.... I probably need some other test equipment.

The shift cutoff sensor works according to the DVM when the switch is activated. I did note that nowhere in the shifters range did the switch activate, I can only make it . I don't know what problems this may be causing? The manual says it causes the computer to deactivates certain cylinders when the switch is activated while shifting into neutral....

Lastly I noted corrosion on the top of the thermosensor. I tested its resistance while connected to the engine (which had been running on and off for at least 20 minutes - so it was at least somewhat warm) and got an out of spec reading. Took the sensor home and performed the pan tests. The sensor is reading out of spec at lower and midrange temperatures. At 212F is the only point it seems to be in spec. For instance at 40F the sensor should read 12,800 ohms. I am registering 119,000 ohms. At 212F it should read between 3120 and 3480 ohms - my reading is 3340 ohms. At 68F it should read 5400-6900ohms, but my reading is 61,000 ohms. Those are the three test points my manual provides.

I think that this sensor is tricking the engine into thinking it has not reached operating temp. Resulting in a over rich fuel delivery and high idle. Does this sound right? Would this be the source of my excessive fuel burn and stumble during acceleration?

Also what effect would the shift cutoff sensor not working have? Is it easy to fix? The manual is pretty vague on its operation....

Thanks,

Jon

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

sounds like you may have found the culprit. the 7*BTDC locked timing indicates a sensor failure.
what was your O2 sensor readings for voltage output?
they should have been about .3-.6 and varying rapidly.
the diagnostic test lamp is only about 70 dollars and will identify anything the ECU sees as a failure by setting a code.saves a lot of time chasing ghosts.
the shift switch only works if the propshaft is loaded, it will missfire the ign system long enough to allow the shift clutch to pull away from the gear.
normal setting on the TPS is to back off the throttle stop,I usually dissconect the linkage, set the TPS at about .5V with shutter fully close, loosen all the shutter screws on the side. note they are right hand threads and are marked with an arrow.
with shutters loose and the idle stop screw backed off and the oil pump link rod removed attach the shutter connector link.
now tighten all shutter screws except the one that rides on the throttle cam with a roller.
now adjust the idle stop screw so the TPS reads about .562V this should get you real close.
now set the throttle roller cam so the arrow on the cam is about the center of the roller.
for test purposes you can insert about a 5K resistor in the connector, fake out the ECU. if the idle timing goes back to normal you found it, if not keep looking.

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

Thanks! I'll try the resistor - basically one of those little ones from Radio Shack? That should be pretty cheap and easy to do. I have my fingers crossed that it is the one.

Its funny you mention the diagnostic light. The tech that came to look at my boat said there wasn't one for the 1998 OX66. Is it what they refer to as the "winky-blinky" sometimes?

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

one and the same.
all v76 motors and all ox 66 motors,all hpdi motors and all efi 4 strokes can be tested with the "winky blinky". only later EFI four strokes and HPDI can be accesed with a laptop.

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

I put a 4700 ohm resitor rated at 0.5 amps in place of the thermosensor, and it did not change the idle speed - or make the stumble go away.

I also was able to check the fuel pressure at the schraeder valve with a gauge. It registers about 35 psi even during the stumble.

I went back and read your post above Rodbolt. The timing is not retarded, its reading 7.5 degrees ATDC, not -7.5 degrees. Thats with the timing picking up the spark from number one cylinder.

Of note, I noticed that the port head warms faster than the starboard head (felt to the touch). Not sure if that means anything.

So the eninge still idles high (1100-1200) rpm and has a stumble/hesitation around 1500rpms.

Also of note - the output voltage on the O2 sensor was around 0.3 volts, and I seem to remember it was steady - not varying. Does the O2 sensor need more investigating? It was just replaced....

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

unless you messed something up it cannot idle at 1100 at 7*ATDC, are you sure its not BTDC?
the O2 sensor is not monitored by the ECU for failures.
ya need to hook up the winky blinky and look for codes.
7* atdc is retarded, BTDC is advanced.
make sure.
TDC is top dead center of piston travel, ATDC is after, BTDC is before.
any O2 sensor output tests have to be done with the gearcase submerged or its irrelavent.

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

Maybe I am mistaken. On the flywheel I see TDC - to the right are numbers that increase to positive and to the left numbers decreasing negative. The timing is about 7.5 degrees positive. I assumed that would be ATDC. Do I have it backwards? I must if you say it won't run at 7 degrees ATDC.

I have called one local Yamah dealer who said he can't get the Winky Blinky and an online Yamaha parts dealer that says its no longer available. I don't believe either response. I will try a local Yamaha dealer that is a little bit further in the morning....

I did the output test with the lower unit submerged. I read the online write up that details the testng of the O2 sensor today. I will do the tests including reading the output voltage while forcing the cylinder rinch and lean by putting your hand over the port on the manifold.

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

the numbers to the left are BTDC the numbers to the right are ATDC. the engine normally idles ATDC. at 7* BTDC it tends to idle about 1200 or so.
if the ECU sees certain sensor failures it locks idle timing at 7*BTDC alerting the operator that a problem has occured.
the winky blinky is readily avalible. I have one of the new style that reads 4 stroke and HPDI and 2 of the old style that read EFI and V76.
last one I purchased was a few months ago to take to venezuela to aide a tech down there.
I did not say it wont run at 7* ATDC, I said unless you have the linkage seriously messed up it cant idle at 1100 and 7*ATDC.

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

part number for diagnostic test lamp,
YB-06795

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

Thanks _ I was able to find that part number yesterday. None of the local Yamaha dealers (3 of them) have it - and say 3-4 weeks. I found an online place in WI that is sending it to me.

In the mean time I plan to go through the linkages to see if they are messed up.

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

Rodbolt - your post along with something I read in the Clymer manual has gotten the situation alot better. You mentioned that the linkages could be screwed up, and the Clymer manual says that a hesitation can be caused by maladjusted linkages. So I went through the procedure on the shift linkage, throttle cable linkage and the throttle pickup timing adjustment.

The throttle cable linkage was way off - I got it better, but I think its still not quite right. The idle has come down from 1200 to 900/1000 and the stumble is noticeably lessened. I have shortened the throttle cable as far as it goes, but it still seems too long. Is there a similar adjustment at the control end of the cable? Basically I disconnected the throttle cable from its attaching point (is this the magneto arm?) and then pushed that arm as far as it goes (throttles closed not wide open) and then shortened the throttle cable to reconnect. It still isn't short enough. Is there another adjustment? Oh the control is in neutral.

The manual says to be sure that the magneto lever reaches full stop open and closed when actuated at the controls. What exactly is the magneto lever?

Things are getting a little better....

 

[John_Madison CT]

Re: 1998 OX66225 hesitation/stumble

Jon: By the time Rodbolt educates you and you work out all these kinks on your engine, you'll soon be the local CT Ox66 expert.

BTW, I'm thrilled Rodbolt is on this forum. His short absence in cyberworld had me panicky.

John

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

Yes John Rodbolt is indeed a fantastic resource!

I have yet another question. Regarding the link and sync for this EFI motor: I guess th lilnk part is the adjustment of the throttle linkage and the pickup timing. Is the syncing the adjustment of the TPS and throttle plates as you described above Rodbolt? My Clymer manual describes the link part, but I am not finding much on the sync.

The winky blinky will arrive today. Will post my findings over the weekend.

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

the magneto lever is what is driven by the throttle cable and drives the throttle cam.
with the history of your motor? I would go through it one step at a time.
start with the shutters, while the shutter link is off adjust the oil pump rod so there is about .010" between the arm and the stopper with the shutter FULLY closed.
then on to adjusting the shutters,TPS and throttle roller.

 

[slapshotjh]

Re: 1998 OX66225 hesitation/stumble

Thanks again Rodbolt - I agree. I get the feeling that all of the things you mentioned need to be gone through methodically.

I put the Winky Blinky on it this evening. It does show a code - Code 14. According to my manual this is the crank position sensor. This is one of the sensors I was unable to test as I don't own a peak voltage meter, or adapter for my DMM. I assume the procedure is to just replace the sensor? Is there any point in getting a peak voltage meter? The manual says to replace it if the peak voltage reading is out of spec. I assume the computer diagnostic is trying to tell me its reading out of spec.

I was told that the winky blinky can only show one code at a time, and that I can clear the first code through the repair only to potentially find more - is that correct?

 

[rodbolt]

Re: 1998 OX66225 hesitation/stumble

thats correct, one code at a time and the lowest number first.
test the resistance on the CPS, if its out of spec replace it.
its rare they fail but they can.
The DVA adapter for most DMM's is 60 dollars more or less.
your making progress anyway