I received a call from Chuck first thing this morning. He had been thinking about our engine and the possible locations where water could get into the crankcase. Although the most obvious answer to the problem is a blown head gasket, Chuck made a recommendation to check our raw water pump. By ruling out the raw water pump first, we could potentially avoid the costly head gasket replacement.
What is a Raw Water Pump
The raw water pump on Banjo is responsible for pulling sea water into the engine as part of the cooling system. By using sea water, which is expected usually to be cooler than the engine coolant, the engine could maintain a proper operating temperature. There is a heat exchange that occurs when cooler sea water cycles around the coolant in the heat exchanger. The raw water pump is the first step in this system. It contains a gear driven shaft mounted to a impeller. The impeller creates a suction that brings the water into the boat.
Pump Location and Disassembly on our Perkins 4.236
Our pump is located on the port-side forward of the Perkins 4.236 marine engine. It is held in place by five bolts. On the side closest is another small plate which holds the main raw water impeller. The outer bolts are removed and the pump will pull straight out of the housing. First, however, we needed to close the main engine sea-cock to prevent water from entering the boat.
Prior to removing the pump, however, several hoses must be loosened and detached from the pump. However, on Banjo, these hoses were very tight and unable to be removed by hand. Therefore, our friend, Harrison, recommended using a heat gun on the low-setting to make the hoses more pliable. This trick worked like a charm and the hoses pulled right off. Be careful not to overheat the hoses or start a fire. Hoses are expensive and easily melted if you are not careful.
Once the raw water pump was removed, we found the same milky-white mixture of water and oil inside the housing. This was to be expected since the engine oil lubricated all of the gear systems for the engine. No issues were found with the pump and the weep area was clear and all of the seals appeared to be intact.
Check out more of our Perkins 4.236 Engine Saga in our boat projects page. A full how-to video is available on our YouTube Channel.