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Bizarre bilge pump mystery

Feb 6, 1998
Canadian Sailcraft 36T Casco Bay, ME
My 2 cents.
Float switches are problematic.
Upgrade to automatic Rule 1100 gph with the built in computer sensor.
As one who is on the receiving end of these pumps daily, I find that the Rule automatic-pumps are as unreliable, if not worse, than their current non-mercury float switches. I would not wish a Rule float switch or a Rule automatic pump on a Somali Pirates boat, okay maybe that's a stretch, and might actually be a good idea. (wink)
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Bob S

Sep 27, 2007
Beneteau 393 New Bedford, MA
My original Rule float switch went for 18 years. I replaced it with a new one and got 2 seasons. As I read this it seems like the problems really began when they removed the mercury? I know I has asked a question about switches recently because I remembered reading something a while ago but couldn't find it in a search. Got the Ultra JR switch you recommended.
Jun 26, 2016
Hunter 1979 Hunter 27 Cherubini Roswell
If your boat were an airplane and this was the Air Force, the crew chief's instructions would simply be to replace the pump fifteen to twenty more times to see what happens.

Hopefully this was helpful.
Jun 27, 2004
Hunter 34 New Bern, NC
In my H34 a check valve is needed to get it to work. Resign yourself to a check valve and keep the bilge clean of things that will jam it.
Jul 28, 2015
Catalina 250 Essington, PA
For those who wish for the old days of mercury float switches, there are some still out there in the supply chain:


I am not advocating for or against them, just pointing it out for you to deal with as you wish. Since they've already been manufactured and are leftover stock, the mercury is already out there and they might as well be used through their useful life before disposing of them.
Mar 26, 2016
C&C 30 Mk I Silver Harbour
A related but pertinent question is: Where is the water coming from that is running into your boat, that requires the bilge pump to be running so much?
May 24, 2004
CC 30 South Florida
Bilge pumps are essential safety equipment keeping your boat afloat if something dire should happen while out sailing miles away from land.
Please allow me a comment on the safety issue so no one might get the wrong impression which could lead to a false sense of security. The small electric pumps installed directly in the bilge of the average sailboat has a lot to do with convenience and very little with safety. These small pumps are rated with no hose connected and fully charged batteries for a short interval , under real life circumstances the average pump would be considered really good if it would perform at 50% of its rated capacity. So a common 750 GPH pump found in a sailboat today would like deliver less than 375 GPH in real life. A significant water intrusion like a broken seacock, or a 1" hole in the hull would easily overwhelm these pumps. The safety pumps that sailors mostly equip their boats with are the manual gusher pumps with access through the cockpit sole to install and operate the pump handle. The small electric pumps at best are good to perhaps buy a little time for someone to notice there is a problem and to take positive action. It might save some of the wood finish in the cabin sole from water damage but will not keep a boat afloat. These pumps were designed for the convenience of being able to discharge incidental water that collects in the bilge without having to manually scoop it it out. With the addition of a float switch or other then water is discharged even when the boat is unattended. I know some boat owners that have added a 120V sump pump to provide boat protection when the boat is on shorepower and unattended. Also remember that smaller boats should get the larger pumps as they will fill up faster. There is no substitute for periodic inspection of thru-hulls, hoses and clamps. Do not rely on a small electric bilge pump for safety.
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Jun 16, 2016
Macgregor 26D My driveway
I agree with RB. I have seen this several times. Each time there was no pump, wiring, or switch fault. The problem was a kinked outflow hose. This either reduced or eliminated the proper amount of discharge. That led to the pump shutting down or blowing a fuse due to excessive heat build up. One way to check the pump is to test it in a large bucket of water.
Nov 6, 2006
Hunter 34 Mandeville Louisiana
As Fast Ed says, the 34 either has to have a check valve or a positive displacement pump which wouldn't need a check valve.. In the 25 years I have owned my 34, the valve has leaked through once.. when it was jammed by a piece of wire insulation dropped in there by the current owner:redface: .. I keep the bilge free of debris!..The bilge pump is a RULE 2000 and the switch is a rule mercury switch.. Both have been operating fine since 1987.. (yes I carry spares on board!) The air conditioner/dehumidifier runs water to the bilge constantly .. so the pump and switch and check valve have many, many hours on them.. I am not recommending, I am telling my experience.
Jun 2, 2004
Catalina 400 Muskegon, Michigan
I have an in-mast furling main and a keel stepped mast. I also had a slow leak in my potable water system. This caused an unusual accumulation of water in the bilge. The Atwood 1500 would cycle fairly regularly and would burn out the float switch about once a season. I raised the 1500's float switch about 4" then installed the smallest rule pump I could find at the bottom of the bilge. The small Rule pump takes care of routine amounts of water while the 1500 Atwood stands ready to kick in if/when there is a REAL need. I haven't had a problem since! Where's that piece of wood to knock on!!!! Note: I have since found my slow leak in the potable water system.
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Sep 25, 2008
Hunter 376 San Rafael
Kloudie and Maine are right in their recommendation of an Ultra Junior. I had a new Rule float switch fail in one week. Another in one month. I almost lost twin 8D batteries.
I have two pumps, one now with an Ultra Junior and one now with a similar Wema (stainless cylinder). The Wema will sometimes hang up with debris. Never had a problem with the Ultra.
Jan 13, 2015
Hunter 34 Deep Bay, BC
Get yourself s multimeter and use normal troubleshooting procedures. Connect it to the pump wiring as near to the pump as you can. Or better yet if you have a clamp-on DC ammeter. Try to not disturb the wiring any more than absolutely required.

When the pump is on (add water if you need to to turn it on,) monitor the voltage (or current) and look for sagging voltage. If it sags more than a volt or two, you have a corroded connection to find. Visually you may never see it. If full voltage is present the problem is in the pump.

I do have a clip-on ammeter, and in principle that's a good suggestion. There are two problems with this approach, however: first, I'd have to be staring at it for up to an hour waiting for it to go off, and second the duration is so short (it's usually closer to 2 seconds than 5) it might not even register. Others in this thread have given me an idea for a better way to find it.

I think the consensus among those who carefully read what I wrote is that the problem MUST be in the wiring, and although until now I thought that pretty far-fetched, the more I think about it, the more I realize it is really the only possibility that makes sense. If you consider the system to comprise three components (pump with level switch, Auto/Off/Manual switch, and the wiring) unless I have astoundingly bad luck it can't be the pump (third one) or the Auto/Off/Manual switch (second one), which leaves only the wiring.

And it has to be between the Auto/Off/Manual switch and the pump. Somehow 12V is briefly getting to the manual wire (brown w. white) to the pump, causing it to run. It can't be the auto wire (brown), because it's 12V all the time. Now, it makes sense that the source of the 12V has to be the auto wire shorting to the manual wire. If it was any other source of 12V, the pump would run but the indicator light on the panel wouldn't light.
Jan 13, 2015
Hunter 34 Deep Bay, BC
Have you checked the ground connection for the circuit? Sounds like an intermittent connection on the hot side, as Ken described, or the less obvious negative side.
Several people have suggested this or similar things, but it doesn't fit the facts. Such a connection would cause the pump to not run when it should, not to run when it shouldn't.
Jan 13, 2015
Hunter 34 Deep Bay, BC
rbringle has a point.. the 34 came with a check valve in the bilge pump discharge line because the pump discharge hose has to be pretty long. When that valve gets a little dirty, the water that the pump put into the hose will leak back slowly into the (very small) bilge and the pump will cycle again..and again.. and again.. Think carefully about Stu's note.. and in addition, clean or replace the check valve. That constant cycling will quickly kill the auto pumps. The mercury switches work very well but ya can't buy them anymore.. The ball bearing switches are pretty unreliable as well.. consider a switch as noted in Maine Sail's post: http://forums.sailboatowners.com/index.php?threads/bilge-pump-switch.181318/#post-1323699
You can increase the bilge volume by cutting out the false bottom if you haven't done that already.. Good luck with it..
I actually had exactly that problem early on in this debacle. The original check valve had failed, and it's next to impossible to access. The pump would cycle exactly as described, but it was working correctly, meaning turning on at high level and off again at low. This was temporarily solved by adding a new check valve between the pump and the failed one. That worked for a while, then it started happening again. That's when I discovered a split in the very old piece of hose just on the pump side of the original check valve. Fixed that, and the cycling problem went away. I left everything related to this out of my post in a (possibly failed) attempt to avoid confusing people.

If I didn't make it clear in my original post, the bilge is totally dry when this intermittent starting occurs. Neither the manual switch nor the internal level switch is calling for the pump to start. The bilge is totally dry because in the couple of seconds it will run, it spits whatever little bit of leakage has accumulated overboard (sometimes nothing, sometimes what looks like about a cup). The level never comes remotely close to the point that the level switch will trigger. And my new check valve? Holds perfectly (so far).
Jan 13, 2015
Hunter 34 Deep Bay, BC

There is alot of good input here from the guys. I do also agree with Stu. I gave up on internal float switches years ago. I now only use a separate float switch & past problems went away.

But getting back to your problem, here may be a thought for you. I have 2 twenty foot lengths of 16GA wire.
I have alligator fittings at the ends. I help my friends when they have problems. Even if everything looks right in the wiring, many times just bypassing the existing wiring with my 20 footers, will reveal problems in the existing wiring.

If with the bypass the same problems exist, I would also look at the pump panel itself for problems & maybe bypass this & see what you get.

This is a brilliant idea, and not just for the current problem; I can think of several wiring troubleshooting episodes that this would have made much simpler. This is the next thing I'm going to try.
Jan 13, 2015
Hunter 34 Deep Bay, BC
After 3 tries maybe the problem is you? Or at least your understanding of how these pumps work.. I have one of those Rule pumps and what it does is turns on every 2 min and looks at its' input current . A lot of current = water being pumped if so it pumps until its input sucks air. Unfortunately what happens in my boat is the water in the line runs back through the pump and restarts the cycle so it tends to cycle based on the last little bit of water in the line and a low volume bilge sump. So I think in the end the ratio of the sump area to exit pipe volume determine how well these pumps work
You're correct, except that's a different model of Rule pump. The two that I had (RuleMate 500 and 750) don't do that, and the Attwood Sahara certainly doesn't either.
Jan 13, 2015
Hunter 34 Deep Bay, BC
Get a stupid float switch and a simple pump and stop messing around with the dumb electronic carp.

story will be over, very soon.

Good luck. :)
The first two pumps had the electronic internal sensor, and I agree that I wasn't impressed. I sometimes get a black mold in the bilge that looks like oil but isn't, and that seems to confuse them. That's what I meant when I said keeping it clean seemed to help. The current pump has a float switch, so I'm already where you're telling me to go.
Jan 13, 2015
Hunter 34 Deep Bay, BC
The Rule Mate is an automatic pump. Why is there a float switch connected to the circuit? At best you would have a conflict between the two switches. Bilge pump switches are considered unreliable and to have two independent ones on the same pump is not good. Listen bilge pumps are not an indispensable system requiring high tech components, so get a manual 500 GPH pump and a float switch and as long as they do the work of expelling incidental collection of water you should be good. Like Stu suggests "stop messing around with the dumb electronic carp" I think he meant "crap".
The current Attwood Sahara has an internal float switch. The two RuleMate pumps had the internal electronic level sensor. At no point were there two level-sensing switches at the same time. However, there would be no problem if there were, as long as they were wired in parallel and not series. Even in series it would kind-of work, but would require both to trip to start the pump, and the first one to reach the shut-off level would stop it, leaving the other one in limbo.
Jan 13, 2015
Hunter 34 Deep Bay, BC
My 2 cents.
Float switches are problematic.
Upgrade to automatic Rule 1100 gph with the built in computer sensor.
Pump comes on every 2.5 minutes for a brief check to see if there is any water to pump. This gives you an audial confirmation that all is good without having to uncover the bilge. Get them on Amazon for $65.
Next it is usually the ground wire or the float switch.
Use a portable car jumper as a power supply and hook it directly to the bilge pump. If the pump works properly on the independent power supply run a new ground wire. If that doesn't work run a new positive wire.
As I said elsewhere, the (current) issue isn't that the pump doesn't run when it should, it's that it runs (very briefly) when it shouldn't. Neither the level nor the manual switch is calling for it to run.