[C320-list] Engine Temperature Gauge Failure

[Bob Borelli]

Clay,

The Alarm Horn and High Water Temp. Red lamp on the Control Panel should activate if the M30 overheats.
The sending unit circuit is attached to these 2 parts.

Most likely cause of overheat is failure of the raw water impeller.
When I drive my boat I listen for the 'splash' sound of the exhaust.
Continuous splash reassuring no overheat.

For the temp gauge I would check for loose wiring on the back of the gauge first.
Sounds like loose wire.
Four wood screws hold the M30 control panel to the pedestal behind the wheel.

Two hot water sending units on my M30.
One threaded into the manifold behind the alternator on the left side of the diesel.
Looking aft point a flashlight above the alternator & it is visible.
I could not reach this sensor without removing the alternator.

The sensor on the right side of the diesel is the oil pressure sensor.

Second temp unit threaded into the top of a tee fitting threaded into the top of the water pump,
with the two hoses attached, supply & return to the water heater under the galley sink.
I would look at the wire attachments here.

Next place to look is at the wiring harness connection, check for loose wires.

If the engine overheats the Alarm Horn and Red Lamp should go off.
They are wired in the circuit before temp gauge.

Bob Borelli 1995 no. 209 & Perkins M30

________________________________
From: C320-list <c320-list-bounces at lists.catalina320.com> on behalf of Clay Carter <fclaycarter at yahoo.com>
Sent: Saturday, October 17, 2020 8:54 AM
To: C320-List at catalina320.com <C320-List at catalina320.com>
Cc: Clay Carter <fclaycarter at yahoo.com>
Subject: [C320-list] Engine Temperature Gauge Failure

Since acquiring hull 225 with Perkins M30 last year I’ve noted my gauge instead of maintaining 180 degrees, instead seems to dance while underway as if from vibration from say 120-200 degrees. While frustrating to read this had never been a problem and engine is great with no issues. Yesterday it has stopped working completely while on a weekend trip. Anybody with suggestions about what/how I can troubleshoot this while now away from port?  The gauge might simply need replacing or perhaps loose wiring or bad sending unit etc.. Where is the sending unit location?  Finally, is the temperature overheating alarm part of this gauge and/or sending unit or is it entirely separate?  Of course I’m concerned about overheating while away and having no alarm to notify me of the danger. Thanks for any input.

Clay Carter
Hull 225
We’ll Sea
Alamitos Bay, CA