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bummer! Looks like YDS doesnt work for OX66 engines. "Important: The software will NOT work on Yamaha OX66 fuel injected engines, Yamaha carbureted engine, or MAC computers!"

Good morning (AK time). I’m having mid to low RPM surging issuesw my 2005 Saltwater Series OX66 200hp. For the full story and diagnostics it’s all in the “OX66LP pumps” thread. HOWEVER, my current thought is the TPS. When I test resistance, w cylinder 1 disconnected and fully closed, I’m...

Thank you Wilton, The injectors were just cleaned and supposedly recalibrated to spec 3 weeks ago. Anymore thights on the TPS? I’m at start a TPS thread so folks dont have to read this novel

Ok. 1 more update for tonight. I double checked the on outboard fuel filter. Super clean no water. I again checked the resistance from the TPS. In neural it was 1.4. With linkage to valve #1, ensuring fully closed, Resistance is about .9. I kept checking and my son slowly pushed the...

OK the latest... Instead of running in a bucket, I took it down and dumped her in the bay. The GOOD: Again fired right up and actually seemed smoother, idled settled around 8-900. idled out of the harbor and got 'er up on step. again seemed smoother and looking at the fuel flow gage, it was...

next step suggestions? what are the symptoms of a failing TPS? I tested the resistance of it wo ignition. BUT maybe testing the actual volts while running is a better idea. any way to do this without the test wire harness referenced in the manual? Also I was thinking maybe a temperature...

ARRRRGGG! Guess my "feeling" was wrong. Not the O2 sensor! ARRRR I replaced the LP pumps and the O2 sensor. Started in the bucket. fired right up, idled at 600. then slowly brought up to 2000 then 3400. seemed about normal, until about 5 min of running then began surging. Not huge...

Phew. Good. I did NOT adjust.

Thank you all! I did install new plug boots. next steps: 1: shock treatment (how ya doing this?) (seafoam) 2:LP fuel pumps 3: O2 sensor Whatcha use for shock treatment? Concentration? How much? In bucket ok? where would there be crud that I haven’t already cleaned?

Thanks Family, I almost hate to admit it (not sure why) but I did order a new O2 sensor. I guess owe it to 10 yrs of ownership, maintenance, and repairs i have a very strong feeling this is the root cause of the issues. I pray my feeling is right! I’ll wait to adjust TPS, idle, etc until...

Ok tried checking resistance between the black and gray wires (these go to the CDI) on O2 sensor. With both sets of wires disconnected (is this how I should test?) I could NOT find continuity/resistance. This is w no ignition. (Pics attached) W key “on” and white wires attached to their home...

Fully closed and fully opened Pics attached

So I was about to adjust the TPS but I was still thinking about the resistance the jumper wires could be causing. So I filed down my probes so they fit into the harness. And also removed the butterfly valve linkage. Now I’m sure #1 valve fully closed. resistance is 0.76 fully closed and...

Now my thinking out loud... How do TPS get out of wack? It just seems like something that once in adjustment, it should stay in adjustment...

plenty of oil in both tanks, remote and onboard. For some reason, Im still thinking once the other issues, fuel and RPM, are solved it wont alarm. Heck it maybe as simple as a water pump getting old (its only 3 yrs old). Yes, tell-tale was peeing. OR its still hovering around freezing here...

INTERESTING! I just checked the TPS. The probes from my DVM don't fit directly into the wire harness so I just stuck a little jumper wire into the harness. The resistance between the Orange and Pink wire, Which I think is the sensor output starts at 0.98 when in neutral. As the throttle is...

Great. I’ll go check TPS now. Yup. I did follow head bolt torque specs and order.

1 more thing. NO changed props or significant additional weight. Additional fuel burn began right after the first surge, shortly after getting in step. Before that surge 12 gph after that surge 17 gph. And loss of top end rpms.

Sorry, the surging was very slight and kinda hard to identify for 100% sure while the cowling was off and running in bucket. I changed both the head gasket and cylinder head gaskets last spring. Simply because there seemed to be a littleweeping around the outer edges. It was completely...

So for the resistance test, do to test between the black wire and grey wire (they clip above the CDI) or the 2 wire w blue harness that run into the fuse box? Thank you! ...also if you have time Dennis, I posted today’s update in the “0X66 LP pumps” thread. Curious if this sounds like an O2...