C30 MKII Water Heater Wiring and Control

Mar 30, 2020
Catalina 30 MKII Lake Murray, SC
Hello -
I have now owned my 1987 Catalina 30 for just over one year. Since the COVID hit just after I bought it I did have the opportunity to change some engine hoses, fix a companion way/coach top leak, replace all lighting to LED, and other cosmetic issues. I really like this boat. So now I'm ready to use a little more of the functionality this season by filling both water tanks and hopefully having some hot water. So fortunately this boat is very original, not too many modifications so it's almost like a time capsule and in really good condition.

My confusion stems from the water heater. I have studied my electrical panel, followed the wires to the water heater and I can not find an on-off switch. I have looked everywhere. I know the pressurized water system works because I did try that and the on demand pump is working fine. I read through my owners manual and still can not figure out how to turn the water heater on or off when connected to shore power. Surely it isn't only operated by the water level inside the tank and if connected to shore power the heating element just turns on?

My electrical panel also holds no clue and looks rather unmolested so it does not look like a water heater power switch was removed. There is only a reset fuse button for the water heater.

Any idea how a factory water heater with the electric element on a Catalina MKII is controlled?

I'm attaching a few photos of my electrical panel as well as an interior and exterior view.

Any help would be appreciated!

Thank you.

Feb 26, 2004
Catalina 34 224 Maple Bay, BC, Canada
The black button that says water heater IS the I/O for the electric element in your water heater.
Jan 23, 2021
Catalina 30 6352 Newport Beach
Thank you for the thorough explanation and all the photos... very helpful.

I agree with Stu Jackson that the circuit breaker is your on/off switch when connected to shore power. The water heater works only on AC, not off of your DC batteries.

There also is a small AC panel below and to the right of your main panel. We can't see it every well, but one of those switches does not have a label. You might try those switches, too, when you are on shore power.

Most boats also are plumbed to the engine cooling system, so that the engine can heat the water while you are motoring or idling. It takes some time to heat up, but this provides you with hot water when you are away from AC shore power. Check your water heater.... if you see heavy black rubber hoses going in and out, then your water heater works off of engine heat, too. If you only see light-duty fresh water lines that are connected to your fresh water pump, then you do not have engine heat.

It is a beautiful boat! Happy sailing...
Last edited:
Mar 30, 2020
Catalina 30 MKII Lake Murray, SC
Stu and Skipper John -

Thank you very much for the response!

I should have realized that given the water heater button did not have an amp rating next to it on the panel like the other fuses.

My bad. Feeling a little stupid but that’s how I learn.

Again thank you for the comments.

Hoping you both have an enjoyable Memorial Day Weekend!

Aug 22, 2021
Catalina Yachts 30 Lake Huron

Wow, what a beauty of an older C30 you have there!!! May I ask if there is a brand name on the dodger/bimini cover?

Jun 8, 2004
Catalina 320 Dana Point
I should have realized that given the water heater button did not have an amp rating next to it on the panel like the other fuses.
The black water heater button IS a circuit breaker, just not labeled as such, the "other fuses" are also circuit breakers.

Ward H

Nov 7, 2011
Catalina 30 Mk II Barnegat, NJ
Yep, agree with the others. Your only AC circuit, going by the single push button breaker, is the hot water heater.
Very nice looking boat. Good Find!