Electric FWC, the sequel

[ndutton]

About a month ago I experienced a complete failure of the electric coolant pump on my FWC after a very low estimated operation time of 10 hours. The pump was the much cheaper Mustang supercharger intercooler pump, like $59 (made in China, referred hereafter as the Chinese pump). I had no specifications when I bought and tested it but the running amperage and flow were comparable to the 3X to 4X more expensive Johnson CM-30 pump. It worked fine up until it failed. I was fortunate it failed at the slip, more so that I was watching the temp gauge at the time so things didn’t get totally out of hand.

The Failure and Autopsy
It turns out the failure was not electrical as I first suspected. My alternator is pretty aggressive, puts out 14.7 volts. That output level is not by choice or design, it’s how the alternator was manufactured (non-adjustable). I became aware of the voltage during the hot coil, electronic ignition and ballast resistor studies. I thought the high voltage might have beat the stuffing out of the pump. I brought it home and took it apart. The design of the motor is a permanent magnet on a shaft that is surrounded by a coil. There are no brushes and no contact between the magnet and coil. Between the mag and coil is a plastic sleeve that was chewed up enough to bind the magnet thereby locking the rotor. I can't see the purpose of the sleeve but accept it is there for a reason. Reassembling the failed pump without the sleeve allows it to work fine. I was discussing this with another list member and he found the specifications online. The allowable voltage for the Chinese pump is 6 - 24 VDC so that wasn't the problem. The allowable liquid temperature maxxed out at 158F. Now there's a problem, I was running at 180 – 185. I sure could have used those specs before I decided to use the Chinese pump, they would have influenced me away from an attractive price. Speaking of price, I invested $118 + tax in two Chinese pumps (one installed, one spare) which approaches the cost of the Johnson CM-30 at $145 + no tax and free shipping so I didn’t save a red cent going on the cheap.

What to do about it
A quick check of the specifications for the Johnson CM-30P7-1 pump showed it's suitable for temps to 212F so we're good. Well maybe not so good. The allowable voltage range is much, much narrower, 12.0 - 13.8 VDC. According to the Johnson tech I contacted, operating outside those voltages will shorten the life of the pump. I'm way outside the range and striving to get a rock solid FWC system means I should stay within the mfr's specs. I’ve learned my lesson courtesy of China.

I bought the Johnson pump ($145 and free shipping, $75 less than I'd seen elsewhere) and also found an inline voltage regulator with adequate specs to tame the voltage at the pump. I bench tested the regulator and it performed well. Took it to the boat, installed it and couldn't get the output voltage greater than 10.8 volts (input of 14.5V down from 14.7V due to harness voltage drop). After more testing on the boat I found I could get 12.2V output with no load attached but still only 10.8V with a load (pump load). This won't do.

I contacted the seller and described the problem; he suggested I give the regulator higher input voltage. No, can't do that because it will wreak havoc with everything else on the boat, the voltage is a little too high as it is. And that's the last I've heard from him so the inline regulator idea is a no-go. Besides, installing it ahead of the pump gives me added complexity and one more component to fail. Good thing it only cost $8.

I suspect the regulator is affected by the pulsing nature of an alternator. That it worked on the bench suggests the power source for the test was steady. It doesn’t really matter, it doesn’t work in the intended application. Done.

The Solution
The Johnson CM-30 pump is installed and works great. My 100 amp Delco internally regulated single wire alternator I've bragged about so much is off to Lewco Electric in Newport Beach to have its regulator replaced with one a little lower, like 14.0V – 13.8V, the measured harness voltage drop of 0.2V will reduce it to 13.8V maximum at the pump meeting Johnson’s specification. 13.8V was the charging voltage standard for decades with an excellent performance history. If I sacrifice a little charge for the benefit of FWC it's worth it to me. Remember on the Catalina 30 we have no choice other than electric FWC due to zero space at the flywheel.

Tentacles that reach well beyond FWC
With this new, lower operational voltage I recalculated my ballast resistor and the existing resistor is still good, no need to replace but the recalculation needed to be done. Also, at the lower charging voltage I'm now married to conventional lead-acid batteries that I prefer anyway. No gels or AGMs in my future.

[Marian Claire]

Informative report and a good reminder to investigate and think thru all changes. I do not think I have been to the boat in years without a "check this, look at that" list. Mostly due to info gained here. Dan S/V Marian Claire

[Ball Racing]

I see on I believe indigo's site where they have a bracket to mount a FWC pump on the alternator belt drive, would this work on your boat, space wise??
or in general is running another item off the acc. drive to much stress in that system?

[ndutton]

I took a hard look at the Indigo system and decided against it because of what you mentioned, taxing the auxiliary drive. I'm already asking it to push a big alternator. Also, their HX would not work for me. The purpose of the tensioner was to take it easy on the drive and alternator bearings too, just enough tension on the belt and no more. I expect both of these considerations will prolong the life of the aux drive. I'm not saying I have any particular knowledge the aux drive can't handle both, just a gut feeling, y'know?

I guess I should not have said we C-30 guys had no choice. Actually we do, the original Indigo FWC system or electric. Once I decided for myself the aux drive pump was not the way for me, I had no other choice.

One of the advantages of electric coolant pumping is the ability to circulate the coolant without the engine running. It was an unexpected benefit. My pump is connected with a rubberized plug and I made a 12V extension cord that plugs into an accessory plug (the cigarette lighter type) with a plug that mates to the pump on the other end. After filling the system it allows me to purge any air that might be trapped and confirm good flow.

BTW, I freely admit the root cause of the problem described was due to me being cheap beyond reason. I'll know better next time.

[hanleyclifford]

Was the pump installed before or after the exchanger? Seems like the exchanger should be able to get the antifreeze down below 158.

[ndutton]

The pump was installed directly after the exchanger and your point is well taken.

I can't say if the spec for the Chinese cheap-O means it runs fine at 158 and fails at 159 or if it starts deteriorating at 140. It could be the coolant I ran through it too, I dunno. Any way I look at it that commie POS wasn't up to the task.

All the voltage business that followed was aimed at staying within the new Johnson pump's specs.

[hanleyclifford]

With all this recent talk about resistors I have been considering other places they could be helpful in view of the wide range of voltages we see in our systems. For instance, I put a 1 ohm, 10 watt resistor ahead of the depth sounder which seems to stabilize it. Also, I have cobbled a board with 1 and 2 ohm resistors in parallel with individual switches which allow me to add additional flow sequentially. This could possibly be applied to an electric FW pump.

[ndutton]

I thought about a resistor ahead of the pump. It solved the high voltage but killed the idle voltage when the alternator doesn't produce. That's why I tried the regulator instead. It was described as a buck only regulator (step-down) and I hoped when the input voltage was less than the target output it would simply drop out and pass the input through unchanged. It's the low input drop out that differentiated it from a plain resistor.

On the bench I was surprised to find it actually boosted the low input to meet the target output. As I described though, on the boat it was a very different and disappointing story.

[Kelly]

Hopefully Neil won't mind me bumping this post up to furnish more FWC pump information.

As I mentioned before in another recent cooling system thread, I've re-plumbed my entire FWC system for easy switching to RWC in an emergency. This was partly done in response to Neil's failed Chinese pump...a possibly catastrophic condition if encountered under way.

The discussions on failing coils opened my eyes to the possibility of running some of our electronic systems "to death" with excessive Amps or Volts. Following Neil's lead, I've added resistance just before the coil to help stay within optimum operating conditions (after having killed a few coils over the years with very little use).

I've now done the same to my Johnson FWC circulation pump in an attempt to stay within the recommended range of operation: 12.0 - 13.8 VDC input. With an in-line resistance rated at 0.44 Ohms just before the pump, I now have the following results:

COLD
Alternator producing 14.64 V
Charging at battery 14.0 V
Power to FWC pump 13.46V

WARM
Alternator producing 13.2 V
Charging at battery ?
Power to FWC pump 12.24V

So as a first test, these numbers seem to fit the normal operating ranges. I will continue to watch this and make more measurements in order to see changes with varying battery conditions and alternator output. Some tweaking may be necessary in the resistance to get this to come out "just right" but already I feel better about perhaps prolonging the life of these accessories.

[hanleyclifford]

Kelly, That warm voltage figure seems low; why the big voltage drop after warm up?

[hanleyclifford]

One of the reasons I elected to use the engine pump to drive the antifreeze was precisely this issue of heat. The MM 502 is well suited to drive either side but the electric pump was seen as suspect. That is why I chose to run the salt water with a baitwell style pump sitting right on the thru hull. I just completed a round trip to Florida in which I changed the saltwater pump cartridge once (about $50.) not because it failed but because it was starting to "squeal" a little. FWIW

[Kelly]

Hanley,

Stop asking electrical questions I can't answer!

I was thinking that the alternator just kicks in strong at first but since the battery was fully charged before start, there was not much work to do after the initial charging??

Good information on your salt water pump. We'll have to see how the Johnson pump holds up over time before we can build any real confidence...

[sastanley]

Kelly, great timing on the bump.

I've just installed, and had my first weekend run with my Johnson pump circulating the fresh water side. I was thinking the exact same as you regarding a resistor. I have a weird anomoly that I see over 15volts out of the alternator at 1,100-1,500 RPM. any other speed and it puts out 14.8v which is what I want out of it (passive isolator drops the charge voltage on each battery to 14.1v). I have not carefully analyzed the voltage into the pump, but it is somewhere in the mid 13 volt range based on the voltmeter in the gauge pod, however, when I may be occasionally running in that 1,100-1,500 range, I might be sending too many volts to the pump (and other things too..) - but even in the mid 13's I am close to that upper acceptable range of the pump.

I am going to be watching the input voltage to my Johnson pump very carefully to see what I pumping into it. It takes less than a minute at normal operating temp for the temp to shoot up if the circulation pump fails (or you forget to plug it in to the ignition circuit after doing the same type of manual air purge as Neil mentioned above! ) - I think I'll be adding one of those high temp alarms too..as much as I hate the damn thing buzzing at startup, I do not fully trust the electric pump just yet (I never say that when the pump is within shouting distance, good pump! ), & its failure could be, as you said, catastrophic..

[Kelly]

Shawn,

Have you thought about a "switch over" system to cool with raw water if the need arises?

[sastanley]

Kelly..yes, eventually. Even though I consider my current set up a success, I can probably neaten up the hose runs, and I'll eventually remove the strainer once I am confident I am not dislodging any engine flakes into the pump. So, as usual with boats, there is always something to do..a quick option to switch over to RWC is definitely a good fail safe, as my 'backup' pump is the same el-cheapo "China pump" that Neil has. I am not too keen on relying on an inferior pump as a backup in the event the superior pump failed.

The water strainer is a plastic Jabsco..I suspect it was designed to be in front of a bilge, or other pump at room temperature, and was probably not designed for constant exposure to 165°F+ water either. So far its screen has not picked up anything.

Additionally, even though now is when I am doing all the futzing around with draining and filling, I could add another 1" of stand-off behind the HX to get it out from underneath the settee lip a little bit too & give me better access.

edit - while trying to find the strainer specs, I came across this..about the same price as the Johnson CM-30, and rated to 100°C circulation, 1.2 amps and 12.5 litre/min circulation.

Jabsco 59510-0012 pump

[Kelly]

That pump looks pretty good...and at half the weight of the Johnson. Neil found a cheaper Johnson pump available however...and none have failed so far

I'm in the same position as you for the backup pump. That's one of the reasons I've set up the RWC contingency plan...that and the fact that it will be much faster for me to open/close a few valves in an emergency than to change out the electric pump.

[sastanley]

Kelly, there are lots of other factors which we didn't discuss, but the idea of a few valves to eliminate the FW circuit and route sea water back into the block is getting to look better & better.

In addition to the current requirement to change out a pump, you are dealing with hose clamps, yanking/cutting hoses of sharp hose barbs, antifreeze/seawater draining into the bilge, etc.etc.

Lots of additional fallout trying to replace a failed pump, , but a few carefully located valves could easily re-route everything & get the temp back down almost as fast as it went up.

[edwardc]

Why not have a backup electric pump already plumbed in parallel, isolated by valves? Than in the case of a failed pump, move wire, turn two valves, and you're back in business.

[sastanley]

Ed, I gotta buy another one of those ~$140 pumps first.

The only issue I have with the valve idea that Kelly proposes is that I worked really hard to eliminate restrictions where I could..using pipe nipples instead of hose barbs, & cast fittings instead of machined ones. Except for one set of reducers on each side of the pump (3/4" pump fittings to 5/8" hose) my system is pretty free flowing. I think that the rock steady temps that I am able to achieve with only a 2" diameter two-pass HX (maybe slightly undersized compared to most other FWC A-4's) confirm this, although I am not a thermodynamics expert. I worry a little bit if valve bodies/ball valves would restrict some flow.

Quite honestly, right now, the easiet thing for me is to get another Johnson pump, pre-install the same terminations on the wires as I have now, and have it in a drawer. I mounted the pump conveniently on the bulkhead and could in theory swap in out in just a few minutes. The hose fittings on each side of the pump are the plastic style that are much easier to get apart than yanking hoses off barbs.