Carver Owners Forum

I replaced my fresh water pump due to age, noise and slight leakage around the pump diaphragm, with the new replacement recommended. Now the water pressure pulsates/cycles when I turn it on!
Filter is clean, water tank is full, pulsates at all outlets.
Any ideas?

Does your freshwater system have an accumulator tank in line. That will pretty much end the pulsation. I just replaced the freshwater pump on my 3007 Aft Cabin. What a bear of a job it was. After doing the install myself I can now understand why a mechanic wanted to charge me $400 for the install.

I take it you mean the water coming out of the faucet is pulsating. Some pumps are better than others at minimizing pulsations. Accumulator tanks certainly help minimize the effect as well as reduce run time. A pretty common mistake though with replacing anything electrical is the desire to upgrade to a bigger more powerful whatever it is without considering that the existing wiring is designed to carry a maximum load efficiently and safely. Did you replace the pump with one of the same electrical specs? You can bet that the OEM installed bare minimum gauge wire to carry the load required by the factory installed water pump. While the circuit protection device may hold (fuse or breaker), there may be enough of a voltage drop due to insufficient wire size preventing a bigger pump from operating properly. Just a thought, easy enough to check. Does the same thing happen with the charger on or engines running? If not, or not as bad, it's a voltage issue.

Since the original Shurflo is no longer available, I replaced the pump with the Shurflo OEM recommended replacement. The new pump data plate list almost identical values from the old pump data plate.
Does anyone else have an accumulator tank on their fresh water system?

The boat wiring is actually a larger gauge than the pump wiring. All hose fittings are the same size as previous pump fittings.

I'm thinking (bare with me) that the pump is new with the same PSI output so it is cycling because it is reaching it's maximum output pressure without any bleed off. I will check my theory tomorrow by opening several faucets at the same time to see if it pulsates. If it doesn't pulsate then I would think that because of multiple openings in the system, it doesn't reach the automatic PSI cutoff to stop and start the pump.

Am I thinking about this in the proper sense or missing something?

For what it's worth, those pumps all have a different GPH, gallons per hour, my guess is the new pump is putting out a higher gph, thus causing it to pulsate. In this case bigger is not better, and even though they recommended it as a replacement, they may have just sold you a pump. But you did say the plate info all matched, thus my second guess would be the plate reading is correct and the pump is actually bigger that it says. Try removing the aerator from a facet and see if it still pulsates. If it does not, then your faucets are not letting the required gph's to flow, thus pulsating. Try cleaning the facets with white vinegar or CLS to remove any build up. BTW great boat, just bought the same year and model love it. Keep in touch, we'll most likely have the same issues along the way.

I installed an accumulator on my 404. Made a big difference, especially in the shower trying to balance the hot and cold.

If you're still working on it, mine were doing that and my book said to clean all the crud out of the individual faucets. That did the trick.Just take the apart, clean the filters, then a little time in vinegar or CLR.

I'm just throwing some other ideas from being a fluid handling technologist. When pumps are not adequately supplied with inlet flow they tend to cavitate thus causing pulsations. After a waiting time with all faucets off, then turn one on, does the flow start off smooth then quickly start to pulsate? If so this is possibly supply head pressure starvation, ie restriction in the feed line (kinked?) The longer it takes to start pulsating the problem could be with the water tank vent is not venting causing a vacuum. If this is the case, the lower the water level in the tank the longer it will take to start pulsating. (more air to evacuate before restricting flow).
If you put in a higher GPM unit, the original feed lines could be restrictive. If this is the case just crack the faucet with little flow and see if still pulsating. In other words you are pressure balancing if smooth with just a slight flow then feed restriction may be the problem. Final idea is the internal check valves in the pump are faulty. Just ideas.