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Old 11-18-2019, 04:31 PM   #1
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Hydraulic pump for Davit

I'm sure this will be a very easy question for many. My Davit is hydraulic and I have a mild hydraulic leak around the pump. I first detected it a few weeks ago and was unable to tell exactly where it was coming from. I put a couple pads under it. I added fluid to the connected tank but was not sure how full I should make it. So how about 75%. A couple days ago I must have left the pump on after moving the davit to hold my rocker stopper. I guess I was running the genset at the same time and couldn't hear it. When I went to turn it on to bring it all aboard, the pump was on at the panel but not running. I checked it and it was not hot but I was not sure how long it ran before shutting down. There had been some additional leaking. Hard to tell with a flashlight down a little hole how much fluid was left but it was not dry. Maybe 25-50%. Turning the panel davit switch on and off did nothing. I opened the big breaker switch that handles the davit and my windlass and let it rest. Later, I turned it all on and presto back in business. So, I get to home port and even with the pump having been shut off at the panel while still running but the windlass breaker still active, the pump would not come on. I opened the windlass breaker and left the boat with plans to return tomorrow. So I ask, is the possible problem not enough fluid in the tank? But then again, the pump did not shut down, I shut it down last time. Could there have been a thermal overload situation and now the thermal overload switch is getting balky? Any ideas? As I recall this is a Baldor pump and reservoir with a Continental Hydraulics valve.
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Old 11-18-2019, 04:52 PM   #2
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Old 11-20-2019, 10:59 AM   #3
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First order of business, to me, is to ensure the oil level is adequate.

Second is to ensure the electrical controls are working by use of a meter, DMM. used at the last wiring before the motor.

If this seems OK then next would be to turn the thing on and LISTEN hard even if you need to put your ear to it and figure out if the motor is even running. A large screwdriver can also be used with the blade touching the motor and the handle on your ear. NOT FOR MOVING PARTS< JUST TO THE MOTOR BODY>

If no noise then the motor has failed. It may be minor such as worn or stuck brushes.

If noise but no pumping then the pump may have failed or the drive coupling between the motor and pump failed.

Last but not least is if there is no noise then the motor has actually fried itself.
This is actually likely.
These small motors are very high power output intended to be used ONLY for SHORT intervals. They are rated for intermittent use only meaning they will destroy themselves if left running for more than a minute or three. They can literally burn themselves up destroying the windings if left running for more than maybe 30 seconds to a minute.

I recently did this and had to replace the motor. Different use but also a small hydraulic pump drive. My pump now has a new motor and the control now has a MOMENTARY switch installed so when I let go of the switch toggle the switch flips off.

I would consider looking into Cole Hersey switch catalogue for a MOMENTARY switch, MOM ON / OFF/ MOM ON. Or two MOM ON/OFF one for up , one for down. Even if the motor survived.
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Old 11-20-2019, 11:21 AM   #4
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Thank you for your reply. This pump and motor set up has always made enough noise for me to hear it while on deck at the davit. It is designed to run much longer than 1 minute as by the time I turn the switch on at the panel, walk out on the foredeck, mess with hooking up the dinghy, and get the dinghy aboard its not unusual for 5 to 10 minutes to go by. The odd thing is that previously I would just turn off the pump motor from the main panel and not mess with the breaker which is also used for the windlass. The first time it shut down on its own I needed to turn off both locations, let it rest and then it worked like normal. Later, after turning it off at the panel, again I had to "break" the breaker, then reactivate, then it worked. I'm going down to the boat today and will fill the reservoir, and test it out. I still think the most likely issue is a combination of low oil and a sensitive thermal overload. My most basic question is, how much fluid do I put in the reservoir? Full, almost full, 3/4. Not sure what the protocol is.
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Old 11-20-2019, 12:04 PM   #5
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Ricky,
I would start with about 3/4 full. I assume the valve showing in your pic runs a hydraulic motor that turns the winch, that means working oil just goes out and back to the tank, not filling up a hydraulic cylinder, which would lower the tank level.

I wonder if there is a float level switch on the tank. If you have schematic of the circuit maybe it would show up there. If topping off makes it run that could be part of answer.

There should be no significant pressure against the pump at idle because the valve spool in that valve is what is called "open center" meaning the valve at rest oil flows into the center position of the valve and right back to the tank. This takes almost no "work" by the motor and shouldn't cause overheating.

Is the thermal overload on the motor or is it in an electrical conductor that looks for overcurrent? Those things can start to trip at lower and lower loads if they get cycled a lot.

The other good ideas about pump and pump connector above still apply.

Good luck on finding the leak! Might need a mirror and strong light to find it after wiping everything down.
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Old 11-20-2019, 05:08 PM   #6
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Listen for the motor. If the drive coupling between the motor and the hydr. pump has failed the motor will be very quiet. It is the pump that makes 95% of the noise.

Your unit may be able to run longer without overheating but I will stand by my comments about many of these small units have a very short run time allowed. Yours may well be longer but if it is not continuous rated then eventually if left running it will be damaged. If you can get the unit out or get a look at the nameplate and get the model number of the motor Baldor, or a distributor, will be able to tell you what the rating is. It's worth knowing what the rating time is.

Agreed about the 3/4 full oil level. That should be enough to operate.
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Old 11-22-2019, 02:45 PM   #7
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Ok I think this is the final answer. I added fluid, ran it (put the dinghy out). Switched off at the panel. Turned it on at the panel, pulled it aboard. No issues. Also, just for clarification, the hydraulic function is for raising and lowering the boom. The cable is pulled by an electric winch.

Thank you guys for your responses.
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Old 11-23-2019, 02:14 PM   #8
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Glad to hear it was just a low fluid level.
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