If you have two water pumps you have a fresh water cooled engine. The vane pump circulates a coolant mixture through the block and to a heat exchanger. The raw water pump sends seawater through the heat exchanger and into the exhaust.
On a raw water cooled engine, the pump circulates seawater through the block and into the exhaust. No heat exchanger. IIRC, Yanmar stopped selling raw water cooled marine engines sometime in the 80s. From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of svpegasu...@gmail.com via CnC-List Sent: Monday, May 16, 2016 8:28 PM To: cnc-list@cnc-list.com Cc: svpegasu...@gmail.com Subject: Re: Stus-List Yanmar 3HM or 3QM If it hasn't been replaced it is probably a 3QM30. 3QM30F is fresh water cooled. Mine was raw water cooled. It has a vane type water pump for a circulating pump and another below the alternator for raw water. TOA Marine supply has a table to help you id your engine. Doug Mountjoy svPegasus LF38 just west of Ballard, WA.
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