Also, and it may be an obvious one, so excuse the dumb question - does the generator draw fuel from only one tank or both, ie if you transfer from tank 1 to 2, does that cut off fuel to the generator? Thanks in advance

The fresh water pump should turn off if  the taps are closed and there is no leak in the water system. If it keep running and there are no leaks then the pressure switch is not working. Like lots of these things you probably need to replace the complete pump to fix the issue. 

Regarding the generator fuel draw - on our 575 it is only from the port fuel tanks. It is  plumbed directly to the port fuel tank and the position of the fuel tanks selector does not effect it. The selector only effects which tank the drive engine (Volvo) gets and returns it fuel from/to.  

Many thanks

There is a seastrainer for the generator and one for the engine. Ours is accessed from a removable wall hatch on the inboard side of the stbd aft cabin aft of the large engine access panel. The hatch is about 30cms x 30cms. Unscrew the lid and remove the basket for cleaning. Ours can block up with seaweed etc enough to reduce or stop the water flow and cause the generator shutdown. Once I have cleaned out the seastrainer I start the generator and use a small mirror to look into the top of the seastrainer to see if the water flow is strong. If not there could still be a blockage in the intake pipework. We sometime have had this problem and I blow the blockage out with a scuba tank with an air gun attachment. If there is no blockage and still low flow check the impellor on the generator water pump. The impellor blades can break off and reduce the water flow. A friend recently had the same problem and when he checked the impellor there was only one blade left out of 6. 

The sea strainer for our 575 is on the port side of the engine compartment against the aft bulkhead.  Its accessed via the aft cabin access panel.       A few hard lessons on generator issues:

1.   The impeller is unfortunately accessed via 90 degrees and you don't have great visibility while working on it.    You could have broken impeller blades and this will require you doing the work with either a mirror or (like me) using an endoscopic camera to see what you are doing.     When we built the boat I asked Hanse if they couldn't mount the generator the other way (turn it 90 degrees) to make it more accessible for maintenance.  They told me that it would require them to obtain a new CE certification.   Probably true, but still disappointing. 

2.  The sea strainer has a gasket on it.  If this gasket is cracked, torn or otherwise not in a position to seal properly, the system will not prime and you will not get water flow.

3.   I put a clamshell strainer on the outside of the hull over the air conditioning, engine and generator intake.  This dramatically reduced things like eel grass clogging up the strainer.   Particularly on the AC unit which prior had gotten all kinds of "HF" errors when clogged. 

4.   The heat exchanger  on the generator can build up scale over the years.   Descaling with something like "barnacle buster" or some other product will dramatically remove water flow.    This is a fairly quick operation that yields good return. 

5.    I added a REVERSO oil change pump to my boat for both the engine and the generator.   With Panda generators they are already plumbed for this connection.  It makes it a snap to both remove and load the oil.     Not really related to water flow,  but its a maintenance time saver. 

Usually one of my checks when we fire up the generator is looking to see if the exhaust temp is stabilizing .  It usually climbs quickly and then settles in no problem.   The gen set shuts off if the temp climbs over its allowed max.   Its not just looking at water flow.

I confirm fully what rick is saying: the sea water filter is on the port side at the back of the engine room, be careful about air leaks there , I would even refill it with water if your think it's not priming correctly by closing the inlet seacock , and then open the seacock and try again  . however , if you see it's not priming correctly you have most probably to replace the water pump impeller , difficult to access as rick says but doable. the system is safe in the sense it will detect the temperature and shut it off...if that happens , I bet that your impeller is broken. do you regularly replace it every year or two or not ? especially if the sea strainer was not closed correctly , or the system got dried by not using it , using the impeller dry (like you are doing when you try to run your generator after a season) is the best way to melt the impeller blades...

Today’s issue, I’ve located a leak in the fresh water supply ( the pump would not switch off ) there is a leak in the void space at the rear of the aft port side cabin, where the deck shower connector is. Other than the small hatch at the end of the cabin , is anyone aware of any other way of accessing this area and pipework?

Thanks in advance

I had replaced the deck shower unit twice and accessed it by crawling through the small hatch at the aft of the port cabin. It was a squeeze but not too difficult depending on your size. The Hanse boatyard had to replace it when we took delivery of our yacht and they removed the gas bottle storage boxes and reached in there through the hole.  

Before you go crawling into the void,   I assume you have checked the cockpit shower hose and control valve (from the cockpit) to see if they are working properly?    Or at least not leaking...   

I've replaced mine with really high quality stuff easily available on Amazon.   Easy to do.

Might save you a trip... :-)

Possibly the most inaccessible parts of the boat.

Everyday is a school day!

It would be useful, if Hanse, ever read these comments, they build or have inspection hatches where joints are…. Just a thought