I have a 1994 Mk 1.5 with a Mk 35A engine. The high temp audible alarm sounds when the engine is at low RPM even though the temperature gage is showing 160 degrees. Confirmed this by being able to touch the engine block for 5 seconds or more. A good friend and professional marine mechanic surmised it might be an air bubble around the alarm sensor. The alarm stops when I rev up the engine. I ran the boat for a couple of hours under power (heading to haul out for Irene) and had no overheating issues but when I arrived at the yard and idled the engine the audio alarm returned.
I have read the threads on burping the air out of the freshwater system but those issues all involved actual over heating. I thinks this is a sensor issue. We did crack the vent at the top of the thermostat (no air came out). Also there is the surge tank for adding antifreeze in the lazarette and that level is ok.
Thoughts?
Thanks,
Tom Smith
Molly Malone
1994 Mk 1.5, Mk 35a, Std Rig
Tom Smith
Molly Malone
1994 Mk 1.5
Std rig/wing keel
Might be the impeller that is not moving enough water at low RMP, but just enough to cause the alarm to go off.
Also, is it a low oil pressure issue and not a water temp issue?
I use an Infra Red Temperature sensor which I keep on the boat as I have found a number of uses for it including checking coolant/water temp at various points as well as the packing gland. You can get them from a number of sources including home depot. Other uses include checking various points on the engine as well as making sure the coffee is at the right temp!
John Meyer
Hilbre 2135
John Meyer
Hilbre
C36 MKll, Hull 2135
Cabrillo Marina, San Pedro, CA
Tom,
I was thinking of suggesting that you remove the cover to get to your impeller, unless you have done that already. It could be what John was alluding to, the impeller may not be providing enough water to circulate. I replaced my impeller a few months ago becasue it was all chewed up.
Glenn Druhot
Carpe Diem
New Bern, NC
35* 6' 10" N / 77* 2' 30" W
2001 C36, Hull #1965
Std Rig; Wing Keel; M35B
I think "spurious" was the right term. The gremlin has not reappeared so I think there was an airbubble and it found its way to the expansion tank.
Tom Smith
Molly Malone
1994 Mk 1.5
Mk 35A
Tom Smith
Molly Malone
1994 Mk 1.5
Std rig/wing keel