"I have driven for hours with the gauge just above zero and the proof for me that it's the sender is that the buzzer works off a different sender and even when pressure is effectively zero, the buzzer doesn't go off and the engine runs just fine."
Wow... thats pretty risky to me. If the engine is running solid lifters, you may not be able to hear the low pressure indicators (or high pressure limited flow indicators) until its too late and its been hurt... likely catastrophically. I intend to go to a purely mechanical oil pressure and also the water temp gauge when I re-due my console. I've had to replace sensors in a couple vehicles over time... but if the oil pressure gauge or light buzzer does anything out of norm... its always been my practice to shut down.
Also super high pressures generally indicate a blockage... either through a malfunctioning regulation device or an plugged line. Learned this the hard way on Dad's 52 Dodge pickup... it had always run high oil pressure from the day he bought it used... after a couple months it seized. Upon opening up it was totally gummed, crudded up everywhere and had blocked the linage. All the lines had to be opened with wire and pipe cleaners. Turned out upon inquiry that the previous owner (a shoe string relative) had NEVER changed the oil or filter since new... just added oil if the stick said it needed it. Think it had 50000 miles when we bought it... considering its abuse it did well to go that far.
Oil or temp issues... its good practice to always shut down first... well unless you LIKE to buy replacement engines or install head gaskets (smile).
Another idea is two sets of guages... one set electric driven for the topsides console... and a second set of purely mechanical gauges on the engine or in the engine compartment as a backup. Takes nothing to install.
Just my opinion... but I been around and owned a lot of farm, industrial, and regular transportation engines for 45 years.
Exactly, which is something I covered in an earlier post, either here or in one of the other threads, I have a Dodge pickup that was running fine, the oil pressure gauge went low, then returned to normal, then low again. What had happened was that the oil pump drive gear shaft had broken, it is driven off the end of the camshaft in the Dodge engine, and it was seating itself, and then coming unseated, until it quit. The engine never ran even close to hot and the oil pressure would go to zero and then when I turned it off it would come back up to normal for a few minutes. I incorrectly guessed it must have been the sender. I now have a new engine in it, which sucks because I did not want to have to build a new engine for it. The only good thing in that deal is that I built the engine myself, so it only cost me about $500.00 to replace it completely. Most people cannot do that for $500.00, which covered the cost of the complete rebuild kit and having the heads ported and polished in the machine shop.
You can go to a manual gauge on your boat, just make sure the oil line does not have any way to chafe, and cannot get snagged on anything. The oil pressure gauge kits are cheap when you go with a manual gauge, and they are going to work no matter what else is going on. I personally would probably go with a new electronic gauge, in order to link it all together to a chart plotter and systems monitor on a boat over 38 feet, or one which had the option of linking everything together. However, that is my preference and may not be what you would want.