Calypso's Perkins 4-108 has pencil zincs in the raw (salt) water heat exchangers for the reduction gear cooling and the exhaust. The refrigeration raw water system also has a pencil zinc.
The cooling and exhaust systems run the raw (cooling) water through the heat exchangers in an attempt to keep salt water away from the engine block and other expensive to replace parts. The engine block is cooled by anti-freeze circulated through the heat exchanger by the 4-108 water pump and does not have zincs. Look for a bronze bolt head sticking out of where salt water and dis-similar metals spend time together, especially when the engine is off and the water will sit for an extended time. Not all auxiliary engine installations have zincs. Many use raw water throughout. If the MD7 is raw water cooled, in salt water without zincs a careful check for corrosion would be a good idea. Martin Calypso 1970 C&C 43 Seattle -----Original Message----- From: CnC-List [mailto:[email protected]] On Behalf Of Dr. David Montgomery Sent: Monday, March 18, 2013 3:27 PM To: [email protected] Subject: Stus-List Diesel engine zincs Howdy all, So my friend picked up an older boat recently with a Volvo Penta MD7 engine. There is no mention of zincs to be replaced anywhere. Evidently the engine's cooling system draws water from out side and runs that through the engine and out again. Given that the boat is in salt water would it not seem likely that zincs would be needed? Your ideas most appreciated! Dave _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected] _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com [email protected]
