The water pump on my 37.5 cycles every so often. When the tank is full, about every 2 and a half minutes, when closer to empty every 6 minutes or so. There is no sign of water leakage and the bilge is dry. Any ideas?
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If no external leak then
there must be an internal one and that means the pump check valve(s). This is sometimes reparable and sometimes not. You can test it by taking off the pump output and putting a short length of hose that is plugged up on it and turn on the pump. If it does the same cycling then the pump is the problem for sure. If it stops cycling then there is an external leak somewhere down stream from the pump.
there must be an internal one and that means the pump check valve(s). This is sometimes reparable and sometimes not. You can test it by taking off the pump output and putting a short length of hose that is plugged up on it and turn on the pump. If it does the same cycling then the pump is the problem for sure. If it stops cycling then there is an external leak somewhere down stream from the pump.
If the water pump is a diaphragm pump...
And more than a few years old, most likely the diaphragm is failing. The first signs are very short "brrp"s as far apart as several hours...then becoming longer and closer together...till finally the pump runs continuously without moving any water. That usually happens at the MOST inconvenient time. On my own boat it did about an hour before I expected guests to show up for a cruise and dinner on the hook in a cove, which gave me just enough time to run to the marina store to buy a new water pump--which fortunately they had in the right size--and swap it out. The good news is, unless you wait till it quits pumping water altogether, you can buy a diaphagm kit, which is inexpensive and easy for anyone who's even slightly mechanically inclined. Just make sure the make/model/year of the pump (NOT the boat!) handy when you order it 'cuz one size does not fit all.
And more than a few years old, most likely the diaphragm is failing. The first signs are very short "brrp"s as far apart as several hours...then becoming longer and closer together...till finally the pump runs continuously without moving any water. That usually happens at the MOST inconvenient time. On my own boat it did about an hour before I expected guests to show up for a cruise and dinner on the hook in a cove, which gave me just enough time to run to the marina store to buy a new water pump--which fortunately they had in the right size--and swap it out. The good news is, unless you wait till it quits pumping water altogether, you can buy a diaphagm kit, which is inexpensive and easy for anyone who's even slightly mechanically inclined. Just make sure the make/model/year of the pump (NOT the boat!) handy when you order it 'cuz one size does not fit all.
Leaks
In addition to the pump just getting old, or the pressure switch beginning to fail, double check your water heater to be sure it isn't leaking. The thing is, the amount of leak to cause cycling isn't at all great. Just a few drops every fraction of a minute will depressurize the system in time. Yours seems pretty often, tho. Sometimes the amount leaking may be so small, there isn't evidence in the bilge because it evaporates or pools in the false bilge before it gets there. Rick D.
In addition to the pump just getting old, or the pressure switch beginning to fail, double check your water heater to be sure it isn't leaking. The thing is, the amount of leak to cause cycling isn't at all great. Just a few drops every fraction of a minute will depressurize the system in time. Yours seems pretty often, tho. Sometimes the amount leaking may be so small, there isn't evidence in the bilge because it evaporates or pools in the false bilge before it gets there. Rick D.
Water pump
It may be caused by small pieces of debris under the flap valves in the pump. The pumps are easy to strip down and the rubber flaps are removeable for cleaning. I had some small pieces of plastic get into my tank ( don't know how )and regularly had this problem. The pump cycles on and off because the water is leaking back past the valves, the pressure drops and the pump restarts to build the pressure back up. I have fitted an inline filter in the inlet pipe to the pump and have no more problems.
It may be caused by small pieces of debris under the flap valves in the pump. The pumps are easy to strip down and the rubber flaps are removeable for cleaning. I had some small pieces of plastic get into my tank ( don't know how )and regularly had this problem. The pump cycles on and off because the water is leaking back past the valves, the pressure drops and the pump restarts to build the pressure back up. I have fitted an inline filter in the inlet pipe to the pump and have no more problems.
leak
Make sure you check all opportunities for leak in hidden places, like the cockpit shower, around the water heater and wash down pump. There is probably a few drops of water dripping somewhere.
Make sure you check all opportunities for leak in hidden places, like the cockpit shower, around the water heater and wash down pump. There is probably a few drops of water dripping somewhere.
the check valves
I agree with Bill. It sounds like a failed check valve. But don't throw the pump away. Most pump manufacturers sell a rebuild kit at a fraction of the price of replacing the pump, and anyone with minimal mechanical skills can do a rebuild in ten minutes.
I agree with Bill. It sounds like a failed check valve. But don't throw the pump away. Most pump manufacturers sell a rebuild kit at a fraction of the price of replacing the pump, and anyone with minimal mechanical skills can do a rebuild in ten minutes.
Same problem - and fix.
I had the same problem last year with my ~5 year old fresh water pump. There can be at least two different problems (pressure switch vs. diaphram) with most pumps and the cost can be prohibitive if you fix/change the wrong one and then have to go back to replace the second part. The easiest and I think cheapest was to send the pump back (over the winter season) to the manufacturer's service department for tesing and repair. They not only make the needed repair but may provide extra service and maintenance.
I had the same problem last year with my ~5 year old fresh water pump. There can be at least two different problems (pressure switch vs. diaphram) with most pumps and the cost can be prohibitive if you fix/change the wrong one and then have to go back to replace the second part. The easiest and I think cheapest was to send the pump back (over the winter season) to the manufacturer's service department for tesing and repair. They not only make the needed repair but may provide extra service and maintenance.
Ours was doing the same thing, but as it turned...
out, it was a leaking loose sit tub/shower fitting. I was able to get to it by removing the two 8D batteries. The drip rate was about once every three seconds, but enough to cause the pump to cycle every few minutes. Terry
out, it was a leaking loose sit tub/shower fitting. I was able to get to it by removing the two 8D batteries. The drip rate was about once every three seconds, but enough to cause the pump to cycle every few minutes. Terry
Add an accumulator
Yes, your system is probably leaking back through the check valves. You should consider adding a diaphgram accumulator also. This will dampen out the sudden drops when you slowly open the taps. Your pump comes on when the line pressure drops to about 20 psi. Without an accumulator in place this happen immediately after you open the tap. This will make the pump cycle on and off esp. if the tap is barely open. The small accumulators sold in West Marine etc. will allow you to run about 4 oz of water out before the pump comes on, it will also keep the pump from pulsing when the tap is only open a little or you are using the hand shower.
Yes, your system is probably leaking back through the check valves. You should consider adding a diaphgram accumulator also. This will dampen out the sudden drops when you slowly open the taps. Your pump comes on when the line pressure drops to about 20 psi. Without an accumulator in place this happen immediately after you open the tap. This will make the pump cycle on and off esp. if the tap is barely open. The small accumulators sold in West Marine etc. will allow you to run about 4 oz of water out before the pump comes on, it will also keep the pump from pulsing when the tap is only open a little or you are using the hand shower.
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