Bilge pump challenge

[Granton5]

I have 3 Jabsco 36600-0000 diaphragm style bulge pumps in my '85 Chris Craft. This year, the engine compartment one started blowing the breaker after 30 seconds of pumping. I watched the pump work. It starts normal. Steady stream of water. Then the pump appears to pump really hard, the pump stops and restarts, then the breaker snaps. It has a screen at the end of the hose that I removed and no difference. I took it apart and the check valves look great. I switched the motor with the other pump, same result. I got it to empty the bilge by leaving the clamp on the inlet hose loose so it could pull in some air. As soon as tightened the clamp, it turned hard and snapped the breaker. I'm going to change the breaker but I don't think that is the issue. A bad breaker wouldn't make the motor turn slow and jerky. Any ideas?

[deblen]

Check the negative 12V supply connection.

[Rucksta]

Check the supply voltage at the position the pump faults under load.

[wholybee]

I loose or "bad" connection won't cause this, as a bad connection will reduce the current, not increase it.

You need to measure the current. Ideally in a few locations, right at the breaker while the pump is running, and right at the pump. If something is loading the pump, causing it to slow, that could cause current to rise. Something wrong with the motor, worn out bearings, or a short in the coils. A short to ground somewhere, but I wouldn't expect the pump to run for a short time in that case, I would expect the breaker to just trip.

[capt jgw]

Since it's a diaphragm pump I assume there's a hose between it and the bilge. Rubber hose can sometimes delaminate and have a loose piece that blocks the flow when under suction. It can look fine without suction. Try replacing the hose and see if that helps.

[HopCar]

Originally Posted by capt jgw

Since it's a diaphragm pump I assume there's a hose between it and the bilge. Rubber hose can sometimes delaminate and have a loose piece that blocks the flow when under suction. It can look fine without suction. Try replacing the hose and see if that helps.

I like that idea. It sure acts like a blockage somewhere. Could it be picking up something in the bilge that blocks the hose and then falls off when the pump stops? A leaf in the bilge might do that.

A blocked discharge could cause those symptoms but I can’t think of what would cause an intermittent blockage in the discharge.