1989 Catalina 36 Specs: Electrical


The 1989 Catalina 36 we purchased was sound, but completely basic.  Like #basic.  We liked that in a lot of ways, but it did mean we had a lot of electrical work to do just to liveaboard.  Cruising away from shore power would be implausible until we made some changes!

In the first few months, we stuck to labor-only electrical work.  Before our first six day trip into the Gulf of Alaska the following spring, we made some important additions just to get us going. $$$ went to second-hand immersion suits, safety gear, and preventative maintenance.  Meander stayed in this state until after our four week cruise in Prince William Sound this fall.

Winter 2017-2018– big additions are in progress.



There were three banks of different ages and locations:

–(2) 12v group 24 car batteries in parallel, powering the Espar diesel heater and serving as starting batteries for the Universal M25XP diesel engine.  In the unlikely event these were healthy batteries, the capacity of Bank 1 was ~160 Ah@12v and 20hr discharge

–(2) 6v GC2 golf cart batteries wired in series, purpose undetermined, as electrolyte and corrosion had bubbled everywhere and lugs had been disconnected.  In the impossible event these were healthy batteries, the capacity of Bank 2 was~110 Ah@12v and 20hr discharge rate

–(2) 12v group 27 deep cycle batteries intended to serve as a house bank.  In the unlikely event these were healthy batteries, the capacity of Bank 3 was~ 180Ah@12v and 20 hr discharge rate.

Stage 1

P removed all the old batteries.  The two aft sets would never be able to hold a charge.  The house bank group 27s didn’t so much hold a charge as transferred shore power to the 12v system.   N managed to salvage them for a shore project of his, but the other four were exchanged when we purchased the new house bank: (4) 6v deep cycle golf cart batteries from Costco.  If anyone wants to discuss battery selection based on the criteria of performance, cost, and ease of install and replacement–I am down.  I have some very strong opinions!

Best budget batteries, IMO.

Anyways, we were able to reuse the original house bank location.  With a judicious notch in the fiberglass, and a Tetris Master install, the four golf cart batteries fit where the two group 27s had been.  Installed 2S2P, we now have a house bank capable of delivering 410 Ah@12v and 20hr rated discharge.  In practice, we do NOT discharge our bank below 75%, so the real capacity of our bank is about 100Ah at 20hr rated discharge.


Although the general practice for boats is to install a separate starting bank for the inboard, I decided (against N’s inclinations–as this whole electrical system design has been, but success has amended his opinion) to stick with a single larger house bank.  Complex systems are inherently more prone to failure.

Diesel engines can get more starting oomph out of a larger house bank anyways, but I’ve got lots of dislikes for multiple banks.  I don’t like finding a spot for two more golf cart batteries just for a starting bank.  I don’t like extra technology to distribute charging capacity between two banks.  I don’t like extra wiring.  I don’t like 1-2-All-Explode switches.  I don’t believe the hassle of the extra bank is justified.  Lead acid batteries–they don’t like to sit unused.  That starting battery, on an active full-time cruising boat, is still only occasionally used in comparison to the house bank.  A commuter cruiser like ours, despite some long trips, has a sit:sail ratio of about 20:1.  Based on the frequency of use of the land-dweller-owned boats on our dock, the sit:sail or sit:motor ratio is more like 50:1 or 100:1 or more.  A single bank, located in an accessible location, is used, monitored, and serviced more reliably during these long down periods.

If we leave Meander for a while, we can rig a tiny folding solar panel directly to the single bank and due to it’s size, have an extremely low risk overcharging or discharging.  Thanks, Emerald Steel!  (Of course, we don’t need to, thanks to our excellent charge controllers, but it had occurred to me charge controllers aren’t infallible…)

So what if we accidentally kill the house bank?  In the event we really screw up the house bank, the batteries are nice and accessible, and the jump box stored nearby.  Simple.  Robust.  (At least in my opinion!) Worst case scenario, we do a decompression start on the Universal diesel.  (I’m kinda talking out my ass on that last one, we know it can be done and I’ve talked at N about how we would, but we haven’t tried it.)

Anyways, we installed a Blue Seas voltage monitor, an Iota DLS-55 Series M charge controller for shore power battery charging, and a new (ish) 155A alternator.  N got to pick these items, although I may have been as reluctant on his choices as he was about mine.  Ehh.  [I thought for sure he’d pick some stupid car charger with no float charge or adjustable voltage setting, and fry our new bank by undercharging.  Of course, then he’d say it was because I picked golf cart batteries.  Mawwiage.  But no, he picked a decent charger!]

Stage 2

As of this post, we are installing a Midnite Sun Kid MPPT Charge Controller with a Whizbang Junior thingummy.  The charge controller manages our new solar install (the panels are sitting, waiting to be bolted to the bimini frame! Happy days!) Now that we have two sources of dock-free power, I feel even better about the single house bank.

The solar panels should be just about right for a 400Ah bank, with our current power consumption and climate.


But not unless it’s free or our engine completely disintegrates.  It just doesn’t pay back for us.  I choke at the idea of paying a significant percentage of the value of our boat.  But hey, I could totally shoehorn and/or design new boat appliances if someone wants us to put a new battery system through the wringer…..

Unless my design is really screwed up, we won’t need to replace the current bank for at least 3-4 years.  I’ve been following emerging battery technology, and looking forward to seeing what is in affordable production in 2021!



The wiring job matched the batteries.  A hodgepodge of wires, joined with household connectors and several bearing singe marks.  About half the wiring had been redone with excellent quality and brand new marine grade wire, but the installer had clearly put in at least 50% longer wire than each run needed.  Haphazard jumbles of new wire languished in the bottom of the bilge throughout the boat.  Nothing was labeled.

After I hissed angrily at the wasteful excess and muttered imprecations about ‘why even bother sizing for voltage drop’ and ‘what fools these mortals be’, N did something better than talking, and got to work.

Left half:  The panel before nathan (on the bottom) and after Nathan (top) Wow! Right half: left is before, right is after stage 1 of tracing/labeling/coiling excess/removing extraneous.  Note the extra wire coiled until we figure out what to do.  Oy.

First step was to trace the myriad unlabeled wires and label at self-evident locations, such as coming into the panel and at logical access points on the boat.  After that, he trimmed easily accessible wires to appropriate lengths, removed extraneous wiring, and redid connections properly with heat shrink wire crimp tubing (especially at the panel). A few runs needed to be redone because they were composed of multiple pieces of wire linked with electrical tape.  Yes.  Sitting in the bilge.  The damp Catalina 36 bilge.  Sigh.

Power Generation

What looked like an old but decent and operational inverter/charger–a Heart Interface–had terrible reviews online (and stopped working with a POP! about a week after we bought the boat.)

As discussed above, we installed a new shore power charge controller.  Ancillary to that, we decided to dump using a permanently-installed inverter away from shore.  We don’t need it.  Even my laptop has a 12v charging cable.  We haven’t missed the inverter.  Yet.

Right: the new alternator! (Note new hoses and hose runs, new belt.)

N also installed a new (refurbished?) 155A alternator on the M25XP Universal diesel engine.  This tripled the charging capacity of the engine.  Obviously, the extra amperage is only useful during bulk charging, and we’d have to motor for 8-10 hours to really charge the battery bank that last bit for long-term battery health.  However, the (working) alternator made the difference between being able to leave on our first spring sailing trip, and NOT.   Lots of motorsailing in Alaska anyways.

We are currently (late 2017) working on installing two 300W monocrystalline solar panels on the bimini.  600W of solar!.  We are so optimistic, we hope to need the Midnite Solar Kid charge controller’s excess power shunt to a water heating element this summer. HA!

We might also be picking up a Honda 2000EU or Ryobi 2200W generator.  Primarily, the generator, which has a built-in  inverter, would be for boat projects with corded tools, or to take with us to work on other projects ashore.  (Other projects: helping friends build cabins, building another camper, building stuff for the boat somewhere other than the boat, building a dinghy or kayak, running a compressor.)  Of course, a generator would eliminate any need to run the engine to power the alternator, even with a dozen cloudy days.

Excellently, the shore power charge controller plugs into an AC outlet, so charging the house bank with the generator is literally plug-and-play.

Pictures should be available within a week or two.  Pesky holidays are getting in the way of my solar panels!

UPDATE 12/29/18: Combination of holidays and cold/wet weather [HELLOOO Seward]–still putting up the bimini for the solar panels.  Only about a month until we leave–I’m getting a bit anxious about the sheer length of our todo list.  We may have to buy the generator just to power the sewing machine, detail sander, and angle grinder along the way.  Test-fitting the panels tomorrow!

Panels are up, charge controller is mounted, frame is built, but the enclosure is not done and we are waiting on a wiring order.

Power Consumption

Suppose I should have started with this, but in reality, most battery and solar installs are more about budget and space than consumption.   Most sailboats have the same 10 to 15 energy draws.   However, winter travel is different up here in Alaska.  Underway, we run our Espar forced air diesel heater, the autopilot; and at night the radar and the running lights.  Eek! 246Ah!  How on earth did we make up that imbalance on our last two trips?  Easy, N doesn’t like sailing at night.  He’s a motorhead who prefers the comfort of a running engine.  So at least a few hours daily, we wind up motorsailing.  I’m optimistic he’ll get used to waves and darkness, but until then, we get that 155A alternator working hard.

Winter Power Table
Comment: Planning future trips, we are trying to limit daily sailing to less than 20 miles from anchorage to anchorage–with the obvious exception of passagemaking.

In contrast, summer anchoring consumes less than 40Ah daily primarily because we do not need to use the Espar for comfort.  Additional energy savings derive from increasing hours of daylight.

Summer Power Table



5 thoughts on “1989 Catalina 36 Specs: Electrical

  1. Great job! Do you have more picture of how you fit your 4 GC2 batteries under the aft gaming table seat? Specially a picture when the batteries are not there. So far I have 2 group 24 batteries in this space, and curious to see how I can fit more Ah at the same spot.

    Liked by 1 person

    1. I do, I’ll post them on the Instagram account with a quick explanation (IG is so much better for pic management on my end than WordPress). The big trick is to cut a small notch in the fiberglass rim (visible in the existing blog pics) so that you can drop in the golf cart batteries and slide them into place. Side effect–they are pretty immobilized even without straps. I’ll also post a pic of how our battery bank looks now (after adding 600w solar, charge controllers, a small portable inverter, new alternator, rewiring all the engine bits…)


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