Mercruiser 4.3 Oil pressure and water pressure switches (Alarm Circuit)

[Birdsboat]

I want to install an oil pressure switch and water pressure switch with buzzer alarm. My manual shows the switches in the instrumentation overview as optional but doesn’t give an exact installation point on the engine. My water temp sender is mounted on the port side of the thermostat housing and I’ve noticed the Tan/Blue wire which is for the water pressure switch from the harness is coiled up nearby. There’s a blanked off port on the starboard side of the housing. Is this the proposed location for the optional water pressure switch?
My oil pressure sender is located on the aft side of the engine near the top of the block just to the starboard side of the distributor. There’s also a Tan/Blue wire coiled up nearby. Is it possible to install a Tee fitting to accommodate both the pressure sender and the pressure switch at this current location?
Is it possible to use the same type pressure switch for both water and oil?
Part numbers would be appreciated
Thanks
Mercruiser 4.3
Serial No - 0C856945

 

[alldodge]

There’s a blanked off port on the starboard side of the housing.
Is this the proposed location for the optional water pressure switch?

Yes and No, The Temp gauge is on the port side and the Temp switch goes on the starboard side. The Temp switch uses the Tan/Blue wire and when the motor gets to hot it grounds the wire which sounds the alarm horn/buzzer

You can put a Water pressure switch there or connect a water pressure gauge there. If you just want to know when things are bad, install the Temp switch and connect the Tan/Blue wire. Then make sure it sounds your alarm

My oil pressure sender is located on the aft side of the engine near the top of the block just to the starboard side of the distributor. There’s also a Tan/Blue wire coiled up nearby. Is it possible to install a Tee fitting to accommodate both the pressure sender and the pressure switch at this current location?
Is it possible to use the same type pressure switch for both water and oil?

Yes, placing a Tee and attach the Tan/Blue same with water Temp

Should be able to find others, but these will work
Water Temp switch 48952 about $100
Oil Pressure switch 87-805605A1 about $30

 

[Scott Danforth]

I prefer a water pressure gauge.

 

[achris]

I prefer a water pressure gauge.

And for the times you're not looking at your gauges?

Yes, gauges are great for seeing trends, but when you hit a plastic bag in the water and the gauge drops to zero instantly, if you're not seeing it at exactly that moment in time, you can cook an engine. As I try to watch where I'm going, I like the alarm, instant 'HOUSTON, WE HAVE A PROBLEM' moment!

Chris.......

 

[Scott Danforth]

And for the times you're not looking at your gauges?

Im parked/anchored

Was raised to sweep the gauges every 5 seconds, watch the other boaters, and anticipate 10 seconds ahead

That is just me

 

[tank1949]

Depending on your easy access to it, there should be an oil pressure or sender near the factory oil filter location that you may consider relocating. Some motors have been retrofitted with remote and easy access filters. However, if there is a switch or sender near the oil filter, and it becomes defective, it may be difficult to notice and replace. I moved both sender and switch to the top by my distributor via a heavy schedule Y connection. I believe it was 1/8" NPT. As a boater for decades, I learned the hard way years ago that gages are fine, but I want something "SCREAMING" at me if there is an issue. Just my 2 cents...

 

[QBhoy]

Hi. I’d firstly say that you can generally get an idea of what’s going on, even with the usual analogue gauges. But I’d also add, that I’d your engine is an mpi (doesn’t mention), the $200 vessel view mobile device is an amazing thing to have. Tells you pin point real time data and info from the ecu. Twice the engine pressures and temps and all sorts of fuel use data too. Not to mention fault diagnosis too.