Spectra 340C - Interesting feedwater scenario

[sailing4us]

Hello
We have a Spectra 340z that was working fine (mostly) until 2 days ago. Went to make water and unit couldn't get enough water for the clark pump to stroke. Cleaned and cleared seacock and sea strainer. Filters are new. Unit ran and made water for about 3 hours, then you can hear the vang pump slow down and strain to pull water. The feed pressure would drop from 98 to 88 and eventually the clark pump would not stroke.


Rechecked the sea strainer and restarted the unit. Same behavior. Unit runs and makes water well for about 3 hours, then the vang pump lugs down and eventually the pump won't stroke.


I can't figure out what is causing the vang pump to initially run well, but over time struggle pulling water into the clark pump. Ideas?

[sailing4us]

More details:
Changed all filters, including charcoal. Started today at 0945. 95psi on monitor and gauge. 221ppm
1025 85psi on gauge. 95 psi on Monitor, 210ppm
1100 88psi stroking 94 on gauge. 94psi on monitor. 210ppm
1135 80 stroking 85ish on gauge. 93.6 psi on monitor. 227ppm. Vang is growling (low tone) and it very hot
1210 70psi barely stroking 74 on gauge. 93.6 on monitor. 264ppm. Vang is really growling. Shut it down.


This is the third cycle over 4 days with the performance outline above.

Appreciate any insights on troubleshooting this further .

[markxengineerin]

My first guess would be heat- can you put a fan on the pump, or measure the temperature vs. time?

I don't know what you mean by "vang" pump, but some Spectras that had diaphragm style pumps required CPU style cooling fans.

You could measure voltage at the pump and make sure it's not dropping. If it is, maybe a wire or connection is overheating.

Another (tougher to do) troubleshooting step might be to run the pump directly plumbed in and out of the ocean with no filters or Clark Pump involved. You would need a pressure gauge and a valve of some sort to create a restriction = 90 psi or whatever level you choose. If it fails that test, time for a new or rebuilt feed pump.

[sailing4us]

I don't know what you mean by "vang" pump, but some Spectras that had diaphragm style pumps required CPU style cooling fans.


The 340c has a boost pump at the strainer and then a feed pump (vang style) that creates most of the feed pressure for the Clark pump. The head on this pump gets worn and must be replaced. This was done in the last 60 hours of use.


Appreciate your time & thoughts. I'll check the voltage.
I saw a youtube where a spectra owner bypassed the boost pump using a parmax water pump until he could get a new boost pump. Don't think the boost pump is the issue. I know it has power and runs, checked it.

[senormechanico]

I second the suggestion to measure supply voltage at the feed pump terminals.
A poor connection between the supply and the pump could heat up which would increase the resistance at that connection, making things worse over time.

[sailing4us]

Thanks for the advice. I have ordered need brushes and springs. Believe that's the issue as once I removed the motor I cleaned up the current brushes and the spindle drum where they contact. Reassembled and ran the unit. Problem gone.