Volvo Penta 43 V6 on 2000 Four Winns runabout

The first time I took out my b

The first time I took out my boat after purchase (used but in excellent condition) the engine overheated. I was told by the dealer that did the repairs that the raw water pump needs to be changed every 2 years whether working properly or not to avoid being stranded on the lake like I was. The problem is that since that time my heat gauge on the dash has never worked again. I am wondering if the sending unit is out. I ran the boat out of water and know the thermostat is working because once it opened up the water coming out got hot. Is it easy to replace a sending unit? Where do I get a sending unit? Is it expensive? Could it be something else?

"Disconnect the wire from the

"Disconnect the wire from the sending unit and touch ground it it: the gauge should mark full reading when touching ground and zero when disconnected. If this is the case, then the sender is defective. They are neither expensive nor difficult to replace.

http://www.volvopentastore.com/INTAKE_MANIFOLD_FUEL_PUMP/dm/category_id.342379-- cart_id.576176356--session_id.844546439--store_id.366--view_id.311843

http://www.marineengine.com/parts/part_details.php?pnum=SIE18-5897&returntopage= 80240776.htm

If after disconnecting the wire and touching ground with it the gauge still doesn't react, then either gauge does not work or the wire going from the sender to the gauge is either open or grounded."