250HP OX66 Surging at 3700rpm

[DennisG01]

Hah! Good idea about grinding a socket down. Silly me, I should of thought of that - I've done the same thing for access to the middle bank of spark plugs on certain inboard manifolds. One of those "custom tools"

Gotcha on the air tool - I figured an O2 sensor might be too sensitive for the shock, but wasn't sure. Thanks!

 

[lime4x4]

If u already ordered the socket u can also put hose clamps around it to keep it from spreading open. Actually we had pretty good weather while we were down there. i was hoping to get the searay into the ocean for a little but when we saw the breakers and how bigger boats then us were getting thrown around we decided against it...lol. But there was one bow rider about 17 feet long that was determined to get into the ocean. Took him a good 45 minutes till he finally cleared the breakers

 

[seasick]

The O2 socket was a little too thick - wouldn't slip past the wall of the "block" that the sensor is screwed into.

I'll try this one: http://www.amazon.com/CTA-2064-Oxygen-S ... sor+socket

Unless anyone has a better suggestion?

Assuming you have a new gasket for the O2 housing, you can remove the bolts and the housing with the O2 sensor still screwed in. Then in the shop you can remove the O2 sensor with a deep socket or as I have done use a appropriate spark plug socket. Be careful not to put stress on the neck of the sensor, it is pretty easy to break the ceramic.
If you want to check/clean the spool (thimble) you are going to have to remove the housing anyway.
(as mentioned, a new gasket should be installed when reassembling)

 

[DennisG01]

All excellent suggestions - thank you!

The thin wall socket worked. I'm sure the x-number of days of PB Blaster helped, too. This is still the spare engine I'm messing around with, until I get up to Maine next week. I ended up taking off the mounting block, as well, and cleaned up the caked-on carbon deposits. I'm planning on cleaning the O2 sensor on the main engine, and then reinstalling with the cleaned block and a new gasket.

By the way, the service manual says the Ohm spec on the white-white wire of the sensor is 100ohms. My spare sensor is reading 7-10 ohms. Is the sensor OK as long is it isn't reading ABOVE 100ohm?

 

[seasick]

All excellent suggestions - thank you!

The thin wall socket worked. I'm sure the x-number of days of PB Blaster helped, too. This is still the spare engine I'm messing around with, until I get up to Maine next week. I ended up taking off the mounting block, as well, and cleaned up the caked-on carbon deposits. I'm planning on cleaning the O2 sensor on the main engine, and then reinstalling with the cleaned block and a new gasket.

By the way, the service manual says the Ohm spec on the white-white wire of the sensor is 100ohms. My spare sensor is reading 7-10 ohms. Is the sensor OK as long is it isn't reading ABOVE 100ohm?

If you are connecting to the correct terminals AND your ohm meter is accurate, 7-10 ohms is way out of spec and would indicate a bad sensor heater. The heaters don't fail that often and often when they do they present an open circuit ( high ohms).
If a good heater circuit reads 100 ohms normally, at 10 ohms if would draw 10 times its normal current. That probably should either blow a fuse or cause a problem with the ECU.
If the heater is bad, the O2 will not output correct values when it is not up to temp but when fully warmed up, it can work fine as long as the sensor section is working.
I doubt that your surging is a result of a bad heater circuit in the O2 sensor.
Since you have the manual, run the electrical output test using a propane torch ( don't overheat it!)

 

[DennisG01]

This is still on the "spare" engine/sensor - just trying to figure things out before I get to the boat. I agree - has nothing to do with the surging - just have gotten a little off track here (the O2 sensor is something I didn't get around to checking before hauling the boat to Maine - I'm in PA).

Yes, to the best of knowledge this DVM is accurate - it's not a "cheapie" and I've had it for about 7 or 8 years and has always been consistent with other's DVM's.

With about 10-15 seconds of heat (propane), I get approximately +7V (positive lead on black wire). Removing the heat causes the volts to drop, within a second, to -.3V. As the sensor cools (say about 15 seconds of time), the volts start to climb, getting up to +.3V. I repeated the above and got similar results. Volts change rapidly with the application or removal of heat... which is a good sign, yes?

 

[family affair]

Imo a bad O2 sensor can contribute to surging. If the O2 sensor is bad the engine runs the richest air/fuel mixture possible. This means the fuel pumps are nearly running at full capacity under load trying to keep up. If a pump is bad, the high pressure pump gets starved for fuel, thus surging.

As for the O2 sensor testing, we could not get ours to perform as the Yamaha test procedure suggests despite cleaning and visually inspecting. The sensor was very slugish to respond. If you suspect a bad sensor, let me know. I have a part # for an identical replacement (minus the plug) for a fraction of Yamaha's price. We have been running it for 3 years now. Perfect performance.

 

[DennisG01]

Thanks, Family. Yes, regardless of whether my O2 sensor is the culprit, I'd be interested in hearing more about the sensor you found. I'm starting to make a list of various components and replacements. I've read a few tidbits here and there about using non-Yamaha O2 sensors, but no one has ever given a long term report. I'm not against using OEM products (I work part time at a Sea Ray dealership), but there comes a point when... Wow! The HP pump and filter hat is another one - looking through my supplier catalogs a few weeks ago I thought I found a replacement at about 1/3 the cost. Haven't looked any further at it, though.

 

[seasick]

This is still on the "spare" engine/sensor - just trying to figure things out before I get to the boat. I agree - has nothing to do with the surging - just have gotten a little off track here (the O2 sensor is something I didn't get around to checking before hauling the boat to Maine - I'm in PA).

Yes, to the best of knowledge this DVM is accurate - it's not a "cheapie" and I've had it for about 7 or 8 years and has always been consistent with other's DVM's.

With about 10-15 seconds of heat (propane), I get approximately +7V (positive lead on black wire). Removing the heat causes the volts to drop, within a second, to -.3V. As the sensor cools (say about 15 seconds of time), the volts start to climb, getting up to +.3V. I repeated the above and got similar results. Volts change rapidly with the application or removal of heat... which is a good sign, yes?

I assume you meant .7 volt not 7 volt
If so, and the voltage changed after applying heat for 10 seconds or so then the sensor is probably good. Keep in mind that the heater can still be bad but that is not that common a fault.
If the spool is clean and the hole to the cylinder is clear, I would guess that the whole O2 operation is fine.

 

[DennisG01]

Oops. Yes, you're correct - ".7V". I just double checked, too. The first time (double checking) 10+/- seconds registered .3V. After that (since it was already warm) it would then register .7V to .9V. All times, though, the V changes rapidly with heat on/off. This is good news - now I have a spare. I'll check the one that's in the boat next week.

 

[DennisG01]

Up in Maine with the boat, now. I have not had the hood off, yet, but I did experience some surging. It's more of a slight variance in RPM followed immediately with the RPM and speed starting to lower. However, I believe it might just be a loose throttle cable or control - at least that's what it seems like since if I play with the control a bit it settles down. Over the course of three short trips (about 1.5 hours total) it happened twice. I was running, for the most part, between 3600 and 4000 RPM.

 

[DennisG01]

Today I had the surging my brother was talking about. Running at 3700RPM, calm waters and light load. After a few minutes, the RPM's would drop to 3500 for about 20 seconds, then back up to 3700 for 20 seconds, then back down. This cycle kept repeating - seemed pretty consistent in the way it was repeating. I still need to pull the hood and trace the fuel lines - but the instance from my post above was different than this.