Good read :
https://www.nzefi.com/bosch-lsu-wide...O63lpw3nmFQAu8

explains why turning on my FAST AFR meter after getting on plane helped make the 0`s last much longer .

In the warm-up phase at engine start, the sensor is operated with reduced heater power..……. The heater power must only be increased when the presence of condensed water in the exhaust gas system can be ruled out.”

“The sensor ceramic element is heated up quickly after heater start. Prior to heating up the ceramic element, it must be guaranteed that there is no condensed water present. This could damage the hot ceramic element.”

“Never switch on sensor heating or the control unit before engine start.”

“….. the sensor installation location design must be selected in a way to minimize, or eliminate, condensed water on the exhaust gas side from contacting the sensor. If this is not possible by design measures, the start of the sensor heater must be delayed until demonstrably no more condensation water appears.”

• Mechanical shock – remember that 1mm thick ceramic wafer on a LSU4.9? It wont handle excessive vibration, being dropped or the exhaust system it is fitted to making contact with the ground (ripple strips etc).
• Contamination – Oil burnt as part of the combustion process (worn out four stroke, or any two-stroke or rotary applications) or worn out turbo seal rings will reduce the life expectancy of a sensor. Particulates from an excessively rich tune, lead from leaded fuels, anti-freeze from a blown head gasket or excessively applied silicone sealant are other possible contamination sources.
• Excessive EGT – While LSU4.9 sensors are actually rated to be able to withstand exhaust gas temperatures as high as 980 degrees C, if the sensing element goes too far above the controlled target temperature, then many aftermarket controllers will enter a fault mode. In the fault mode the controller may stop controlling the sensor which is effectively like not having the controller turned on at all while the sensor is fitted to the exhaust. Therefore continuing to drive while the controller is in a fault mode can kill a sensor that would otherwise be fine. Resetting the controller to get it out of fault mode can typically be done simply by turning the controller off and back on again.

Thanks, good info

Well that explains it ! Ive lost several 4.9s tuning boats and PWC's , now I know why.

I started using these on boats, makes a world of difference!
https://www.innovatemotorsports.com/...-p-n-3729.html

NTK sensors are more hardy if you have an option to run them.

Ive had good luck with units similar to these:

Ditto. I've run without this but prefer having it installed (as I do now). I have also done direct A - B comparison on AFRS with and without the unit installed. Zero difference.

I agree they hold up a lot better in the marine world.

i was doing a difficult tuning job on water on a whippled twin engine baja. The motors loads NEVER matched so we actually had to spend alot of time pissing around on water. The guy had lightning headers, this thing killed 02 sensors left and right. His answer was just to buy more and more sensors. I was taking 5 or 6 with me each time we went out on water, major pia. Bought those innovate extenders with directional hole, sensors would last hrs in stead of minutes, fwiw, smitty

Trouble shooting O2 sensors on my 2010 Sea Ray Sun Deck. 350 MAG engine. I can view the sensor output while engine is running. Trying to track down why one sensor the 'D' sensor, which I believe is the port side post cat sensor (might be wrong on that) not at boat at the moment will randomly go to zero. Sometimes it works great, then suddenly goes to zero. I have recently tuned up the engine with routine maintenance. plugs, plug wires, rotor, rotor cap. The issue occurred before the tune up and after. Over the past 2 seasons I have even replaced all four O2 sensors. Still getting this random issue, but is happening more frequently this season. No good knowledge base mercury marine guys at my marina and where I bought the boat is too far away. So trying to troubleshoot what may cause this. Any ideas? Vacuum leak? Short in fuse, wiring? Faulty PCV? I assume (uh oh) its not the cat itself. The boat runs beautifully, no hesitation, rough idle, etc. Just this random O2 reading 0 when the others are bouncing around in the hundreds to thousands range. When the reading goes to zero I get the smart craft O2 sensor alarm. O2 exhaust system failure, Fuel too lean, sometimes too rich. Any idea from anyone that has had this issue or with knowledge of the 2010 350 MAG engine? I believe 2010 was the first year they put emission control on the boat engine and trying to troubleshoot the issue.

Thanks in advance.