Hotstart thermosiphon type engine heaters - pressure switch ?

[Milacron]

Now that even lower coastal SC is getting a little chilly, I start thinking about leaving my engine heaters on. These are Kim Hotspot model CB tank type, one for each Detroit 12v71TA. When I first bought the boat in April, I could turn on the appropriate circuit breaker, two relays on the wall would engage and provide power to the Hotspots. But during the summer the engines would get too hot so I didn't use the Hotstarts.

Now, when I turn on the same breaker nothing happens. I can force the relays on with alligator clip and the heaters work just fine...so something up between circuit breaker and the relays. Circuit breaker has good continuity and voltage, cleaned minor corrosion on terminals at relay...still no cigar.

Hotstart wiring diagram shows a pressure switch in there somewhere. Might be helpful to know more about this....is the purpose of same to automatically disconnect the Hotstart relays when the engine is running ? If so I wonder if I have a separate oil pressure switch that is stuck. OTOH, would think there would be one for each engine and a curiosity if both stuck.

FWIW, my regular oil pressure monitoring systems work perfectly...both electric send units and direct mechanical. Any ideas what might be keeping my Hotstart relays from getting coil voltage ?

 

[Milacron]

Nevermind....found the problem and fixed it (was oil pressure sensor related). Now the question is, is it perfectly safe to leave these heaters on 24/7 when at the dock ? (and obviously, engines not running)

 

[Milacron]

OK, here's the scoop (called Hotstart)... if your unit has a thermostat (not all of them do) and you can hear it click on and off, AND you have "serviced" thermo every two years (i.e. take thermo apart and clean and make sure the solenoid works ok...don't need to drain coolant to do that, btw), it is ok to leave Hotstart on 24/7.

I had to leave the boat a few minutes after fixing my relay system, so dunno on mine yet....plus I need to service the thermo....

Anyhoo, even though I'm talking to myself at this point, thought this might be of interest. If not, moderator please delete.

 

[davidwigler]

I plug mine into these digital thermostats:

http://www.amazon.com/dp/B000E7NYY8...vptwo=&hvqmt=b&hvdev=c&ref=pd_sl_8o4a8ccdc9_b

Set the temperature of the ER to 55 or 60 degrees and save some power. It's amazing how little energy it takes to maintain that temp, and in a couple of hours you can have them at 70-80 degrees for easy starting.

 

[Milacron]

I plug mine into these digital thermostats:

http://www.amazon.com/dp/B000E7NYY8...vptwo=&hvqmt=b&hvdev=c&ref=pd_sl_8o4a8ccdc9_b

Set the temperature of the ER to 55 or 60 degrees and save some power. It's amazing how little energy it takes to maintain that temp, and in a couple of hours you can have them at 70-80 degrees for easy starting.

I used to do something like that with my Egg Harbor 40C...except I simply had the plug in thermo connected to a small ceramic space heater as it had no integral engine heaters. Not so much for easier starting but just to keep things in there from freezing in a Hampton, VA winter.

In this case, the Hotstarts are pretty large and require 230 volts....apparently the 8V71TI's use a 115 volt system.