one of these hooked upto a piezo alarm can be set to keep an eye on your raw water flow /output on your engine by strapping the sensor to your elbow .may just help if raw water inlet gets blocked suddenly/
http://www.ebay.com/itm/DC-12V-BLUE...003?pt=LH_DefaultDomain_0&hash=item4cff37c703
and the buzzer
http://www.ebay.com/itm/1-Piece-Pie...258?pt=LH_DefaultDomain_0&hash=item33729cc6ea
1+2 to an alarm or a lamp or whatever you wish to be informed by
3+4 12v supply.
cheap and cheerful but may help someone
http://www.ebay.com/itm/DC-12V-BLUE...003?pt=LH_DefaultDomain_0&hash=item4cff37c703
and the buzzer
http://www.ebay.com/itm/1-Piece-Pie...258?pt=LH_DefaultDomain_0&hash=item33729cc6ea
1+2 to an alarm or a lamp or whatever you wish to be informed by
3+4 12v supply.
cheap and cheerful but may help someone