[C320-list] Perkins M30 diesel water temperature sending units

[Bob Borelli]

I was cruising at 2800 rpms when I smelled burning, looked down at the Engine Water Temperature gauge on the M30 Control Panel and realized the diesel was overheating due to the Jabsco raw water pump vane failure.



Question is why the Control Panels Alarm did not sound off and the High Water Temp. Red light not activate?  It maybe corrosion on the wiring harness, I plan to clean this next trip to the boat.



But I traced the wiring from the Alarm and Red light to a brown Sending Unit threaded in to the top of the water pump on my Perkins Perama M30 103-10.

This is a brown colored sending unit with 3 posts on top: 1 wire grounded to the block, 1 wire to the Alarm & Red light and 1 empty post.



I expected this wiring to be attached to the port side single post sending unit threaded into the cylinder head located behind the Alternator below the heat exchanger.  As indicated on page 42 of the Perkins M30 Operation and Maintenance Manual & apparently on page 98, item 28 of the Perkins M30 Parts Manual.  And not this brown unit on the water pump.



The Alarm & red light is also wired to the Low Oil Pressure sending unit threaded into the cylinder head on fuel injection side of the diesel which works.



I traced the wire from the Control Panels Engine Temperature gauge to the port side sending unit which clearly does indeed operate the temperature gauge.



But according to page 128 & Figure 5-32 of Marine Diesel Engines 3rd edition by Nigel Calder and the description of a new port side sending unit on ‘parts4engines.com’ website, the single pole sender should not operate a gauge.



It’s as if the wires should be changed from gauge to alarm / light, vice versa. But I don’t want to try this.

I do want the Alarm and Red light to activate next time the raw water pump vanes break off.



So my question - has any owner encountered this sender on the water pump?  How to get alarm and light to operate?  Where to buy new senders?  VDO is one manufacturer.



And I plan to install the Borel raw water temperature alarm on the exhaust just below the injection elbow.  Any comments greatly appreciated, thank you!



New to me my 1995 Catalina 320 no. 209   on the Sassafras River Georgetown Maryland.

Bob Borelli