OX66 Problem

[dunepray]

Hey Guys,
I am new here and hoping for some imput to my problem. I own a 2002 Yamaha OX66 225.
I have been having a surging issue lately at idle that seemed to resolve itself when the motor warmed up at the house. I Went fishing yesterday and she seemed to run fine on the way out to blue water. While *****ing we would pull up when we had a fish on and she would stall while idling. Seemed to run fine when *****ing. When we ran in we got within a mile of shore and she shut down with a high water temp alarm. Lots of weeds yesterday, so I figured something got sucked into the intake. Anyway, we limped in, but the water P-ing out was not hot (luke warm). Today I began checking things over. I pulled the water temp sensor and two switches on each head and checked them and they were within ranges. I ran the motor up and discovered while using a laser temp sensor on the heads and thermostats that I had a hot cylinder on the starboard bank #1 cylinder (175*). I pulled the thermostat and it looked like there was a lot of crap in there, so I dumped about 4 cups of white vinegar and water in the thermostat housing and let it sit for awhile. While I waited for the vinegar to work, I pulled the O2 sensor thinking that it may have had something to do with the shut down. It was clean. I mean really clean, and the dogbone was completely clear. Ran it up again and the hot cylinder had cleared and was running well at the house,.but still surging. I took her out on the water and tried to run her WOT and got to about 5K for a couple minutes and she shut completely down. No water temp alarm. I tried it again and the same thing happened. I'm at my wits end!!

From what I'm reading here I'm thinking maybe I need to check the Throttle Position Sensor or VST and fuel line for leaks or pressure fluctuations.

I've done everything else I can think of, like cleaning VST(was very clean), Hight Pressure regulator filter screen (very clean), changing all plugs, water seperator, fuel filters, plug ends resistance check, low pressure fuel pumps replaced. sync & link, O2 sensor cleaning, etc. I did have one of those cheap fuel pressure guages from Harbor Freight on the VST to check the fuel pressure, but it started pissing gas all over. It was at 35 lbs during the test which was at idle. It now is in the garbage. I'm going to call Simyamaha tomorrow and get the test harnesses and fuel pressure guage, as I've never done these things before. Does this make sense? I am not a mechanic, but I try.

Is there anybody out there who can shed light on this issue??? Am I on the right track??

TIA
Dune

[dunepray]

QUICK UPDATE:

I was out working on the motor this evening and took the shop manual with me. I started right at the general maintenance in the beginning of the manual. Checked all fuel lines. Pressure tested VST. Sync & Link. Set the idle. Then I got to the Throttle Position Sensor and everything came to a screeching halt. No matter what I did to the adjustment, I couldn't bring the TPS below 3.5 volts. The manual says at closed throttles the setting should be .50 +/- .02 v. I think this is what caused the motor to shut down at WOT. Are there any experts out there who can weigh in???

Dune

[jb123]

Do you run ethanol ?
Clean vst/ filter ?
Monitor pressure @ all rpms ?

[dunepray]

Hello JB,
I only run Rec-90 non-ethanol. Cleaned the VST HPFP and regulator filters (they were very clean anyway). I have only checked the VST pressure at idle and it's at 35+. I have to take her out once I get the harnesses from Simyamaha. I worked on her tonight a little and could not figure out how to get the voltage ranges they refer to in the manual. I can get 0.50v at WOT on #1 throttle plate, and 4.12v at closed throttle plate. That's how I understand the manual, which is totally opposite from what or how I understand the motor should operate. The motor should need more voltage at higher rev's. Anyway, I put her back into the same position as before and I'll wait for the TPS harness so I can do a decent job at it. If you can give me some idea of how I'm supposed to accomplish these voltage ranges I would appreciate it. Then I will move on to the next level and hopefully find out why the RPM's fall at WOT. I'm now not convinced that the TPS is the problem.

Thanks
Dune

[rodbolt17]

you most likely have a TPS issue now.
you must verify the 5V reference voltage BEFORE attempting to check the TPS output.
rail pressure at idle is irrelevant in this issue.
you must verify rail pressure at the failure RPM and load.
even if the TPS was removed and tossed in the creek the motor will still run.
the ONLY sensor on that motor that is NOT monitored for faults is the O2 sensor.

ANY other sensor failure will result in base timing locking at 7* BTDC an idle speed of about 1100 RPM.
depending on the sensor top speed may or may not be reached.

99% of your type complaints are fuel related.

[dunepray]

Thanks for the response Rodbolt,
Would you elaborate on how you verify the 5v reference. I can remove the TPS from the bracket and run it from 0-5.01v by hand. If I set the TPS prior to placing it in the bracket at .50v, the crossbar does not line up with the slot in the bracket with the throttle closed. In fact just the opposite. Think of an "X", and that's what I see when I attempt to place the TPS in the bracket. Not until I open the throttle to WOT does the crossbar line up with the TPS set at .50v. And when I do that the rotation of the TPS is counter to my thinking of what the motor needs as it increases rev's. Result: .50v at WOT, and 4.12v at closed throttle. When I placed the TPS in its original position, the low end was in the 3.6v range.

I do understand that I need to get her on the water to test fuel pressure at all ranges, and have been thinking fuel as opposed to electrical lately. I'm waiting for a decent guage and harnesses from Simyamaha. Normally I run the throttle under 4300 RPM when going out or coming in, and really only run WOT from a hole shot or very short duration. I have read on some of the blogs that there is a limiter in the computer mapping that will shut down the motor. And, the blog mentioned the prop in their case was the problem. Could this be what the issue is about?

I have to get past this TPS issue before I can move on. I am determined to take this one step at a time, rather than jump around throwing parts at the motor.

Thanks,
Dune

[dunepray]

ANOTHER UPDATE:
I think I've figured out the assembly of the TPS. Can't get to it right now, it's been pouring all afternoon. Anyway, from my feeble memory the throttle shaft turns counterclockwise, from fully closed to open. I have to turn the crossbar of the TPS to the 5v position and tilt the TPS to meet the full throttle position and install. That should rotate clockwise to the .50v reading. I think that prior to my removal, the TPS had to have been in there the wrong way as I couldn't get the correct reading at closed throttle. Can't wait to get my test harnesses so I can get after this and move on.

Dune

[rodbolt17]

only goes one way.
how you messed it up I have no clue.
the 5V reference is just that.
the pick off voltage starts at about .5 and goes to just over 4V at WOT.
orange to black should be 5V.
pink to black should be about .5v at shutter fully closed(NOT IDLE BUT FULLY CLOSED) to about 4v at WOT.
technician induced failures.

[dunepray]

Thanks Rodbolt,
I got the TPS in the right way this time. I got the new test harnesses yesterday afternoon and right off the bat, got the reading right at closed throttle (.50v). At WOT I got 4.17v, and just like you said. I have read from here and other blogs that the upper end should be at or around 5v, and the rotation of the throttle will not take it that high. I am sitting in my easy chair this morning and was trying to find the answer, until I read your post. Thank You for clearing this up so I can move on. This is exactly as you say, a Technician Induced Failure. I, however, have never claimed the "Technician" status. Just an amateur, but I learn fast. And, admit my shortcomings. If there is something to be learned by others due to my errors, it's that you should have the proper test equipment when undertaking these tasks. Initially, I probed the wires and may have been reading faulty numbers. The test harness gives a clean response from a meter. Once I was getting good numbers within the ranges of Rodbolts numbers, I reset the throttle link and idle setting. As the motor warmed the RPM's settled and was running very smoothly.

NOW, on to water tests. It will be interesting to see if the TPS had anything to do with the motor shut down at WOT.

Thanks Again,
Dune

[99yam40]

Only thing I can think of that will shut down the motor at WOT would be running out of fuel in VST

[TownsendsFJR1300]

We just cleaned the coolant passages and head of my neighbors Yamaha V6 200HP, 2 stroke that was overheating and shutting down.. His issues were a bit different from yours however if you have one cylinder head running considerably hotter (as posted in your first post) than the others, it may very well be clogged with salt...

BTW, two of the 6 cylinder water jackets were totally clogged all the way around. Those jackets are approx 4" deep. To get them cleaned out, they had to be MANUALLY scraped out... He tried soaking the heads in vinegar overnight, didn't do squat. The deeper you dug, the harder the salt was... After the cleaning/re-assembly, ran to WOT without any shut down/overheat, etc...

And the water coming out the pee hole shouldn't be hot, warm is normal.

[dunepray]

Thanks for the response Townsends,
I have been thinking about pulling the water jackets to take a look, but I haven't really had an overheat issue. Just that once, and when that cleared it didn't come back. the engine however, did shut down without a temperature alarm at WOT twice. So far I've run it up in the yard and with the test equipment I've eliminated the electrical end of everything. The TPS and O2 test good, and it seems to run fine now that the throttle adjustments are right. I couldn't get it on the water today due to the weather, but that's next. As soon as I can get it on the water I don't think it will take long to find what's up.

Dune

[TownsendsFJR1300]

His engine would shut down at around 23MPG (his tach died) with the alarms going. Initially we found one thermostat bad, replaced that with a water pump, brought up the RPM's/speed a little bit but still no WOT.

While at the marina, speaking with the highest Rated Yamaha tech (while he was doing some work on my engine), he brought to our attention of this "problem". He currently had one in the shop with the exact same issue.

It should be noted my neighbors engine is run in the salt/brackish water and its rare my neighbor would flush the engine with fresh water (big mistake). I didn't have a thermo gun at the time but do now!

I should have took pictures before and after, we didn't realize how deep the jackets were until we finally hit bottom (aluminum). I don't know how the engine ran as good as it did...

BTW, Yamaha sells different products to help keep the fuel system and top end clean that, in my experiance, works extremly well (Ring free specifically):

http://www.yamaha-motor.com/yamalube...ies/additives/

Should you have any water in your built in fuel tank (fuel is cloudy and water separates after a bit of time) I found a product that helps burn it off (along with Non-ethonol fuel). It took me probablly 6 months or running K-100 with non ethonol) fuel to get clear fuel again, the engine now runs top notch. It doesn't eliminate the water, just keeps it in suspension so it gets burned out with the fuel. My boat is a 1996 with a built in 50 gallon tank (original tank, NEVER been pulled or emptied). I was getting milky fuel and eventually water separation from fuel pulled from the engine-Not anymore). The K100 is not cheap but considerably cheaper than pulling a tank, dumping fuel, etc. I run it religiously with the Yamaha Ring Free.

K-100 site: http://www.k100fueltreatment.com/


Good luck

Scott

[dunepray]

UPDATE:
Over the last few days I received from Simyama the 3 test harnesses and fuel pressure guage. Monday, I received a call-back from ANDY at Simyamaha and he said the TPS is set at closed throttle (.50v) and what the TPS reads at WOT will only be what the throttle position sensor position rotates to in the WOT position. In other words, ANDY said that as long as the TPS goes up/down with the rotation of the throttle plate, it's fine. So, I took the boat down to the water for a test run. Prior to going, I rigged a small 2x18 inch board by drilling holes through it and placing two voltage meters side by side and wire-tying them to the board. I also attached the fuel pressure guage. With the cowel off the motor, I tied the assembly to the plastic throttle body silencer on the front of the motor. Once on the water, I ran the motor to warm it up and then took it for a spin. The first try, out of the hole she did well to WOT for several minutes (4.9k). While at WOT for about 5 minutes it started to bog down (but did not shut down this time) to around 4k. The fuel pressure did not change (35psi). I ran it at several RPM ranges and did not lose any fuel pressure. I tried it out of the hole again and it bogged a little and would only run up to about 4.2k. All the electrical systems were reading fine (O2, TPS, and no temp/oil alarms). The winky-blinky tester doesn't show any malfunctions.

AS RODBOLT SAID BEFORE, I am now convinced this is a fuel problem, and most likely a fuel injector problem, as I've checked/replaced everything else. So, I am going to attack the injectors tonight and attempt to clean them. I built a wire harness with on/off button and fuel injector wiring harness connector I bought at a local parts store, along with a 5cc plastic syringe I got free from CVS Drug Store. I saw a video clip here on THT that showed how to clean them. I'll let y'all know how I make out.

Dune

[bajakeith]

Ox 66

Hi,,do you have a real yammy service manual ?? that motor is a sweety !! she does have a LOT of filters (screen)and I always throw new lift pumps on to start with...injectors don't sound like your issue,,and they should be ultrasonic cleaned and flow rate checked,,IMO...the VST pump filter is a problem as its at the bottom of the tank and gets plugged rather easy !! and the fuel rail has filters as does the fuel reg.. if after going thru the fuel system completely and your still having a problem,, get a can of DEOXIT and go thru ALL electrical connectors...so far I am( it seems) the only guy in this biz that uses this stuff and it really makes FI Motors HUM !!...keep us updated...