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Hi, I'm still struggling with the engine in my 40ft boat, it's a 1.5BMC with bowman header, skin tanks and dry exhaust, smaller diameter water pump impeller which looks to be in good condition. 82 thermostat fitted which tests ok in a pan. After welding up a couple more suspect areas on the starboard skin tank I took the boat out for a spin around Birmingham on Saturday. The trip was a bit of a challenge. The water leaks have all been fixed and the system was bled fully, each skin tank has a bleed screw on the top From our mooring in Sherborne Wharf we got as far as the bridge before the engine cut out, a whole 100yards maybe. It would run ok in neutral but stall as soon as drive was engaged. After pulling up outside Banatynes, getting a late lunch and letting off a bit of steam, we discovered the prop was fouled. So, with that cleared we carried on, the idea being to complete the Lozells Loop as a test run. However as we got around the corner it was apparent there was still an issue with the cooling system, the gauge steadily climbed up and up to the red zone so I shut the engine down. We pulled up, had a check of the system and discovered the port skin tank was stone cold whereas the starboard was warm. The pipe between the two was cold. Last night I drained the tanks, took off all the pipes and gave each tank a thorough flushing for 20 minutes. As I'd been through a similar exercise recently, I hadn't expected to see much rust and sure enough, the water ran crystal clear throughout. One thing that occurred to me is that the gearbox and engine oil coolers are probably not in the best part of the system. They sit, in series, between the port skin tank and water pump with various reducers and adapters in the way. I'm sort of hoping that between the bore differences and the restricted flow through core of the heat exchangers, the pump struggles to lift the water up and around the system and is probably just cavitating. The starboard tank (I assume) heats up through thermo syphoning. If this is the case, a bit of re-engineering will hopefully suffice. Assuming the cooling system is running properly, is there any need for an engine oil cooler? Is there a better place in the circuit to run the coolers? I noticed a picture here recently where the cooler was plumbed through the end caps of the header tank. Any advice or pictures of successful cooling systems will be gratefully recieved. Thanks in advance Robert
- 56 replies
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- bmc 1.5
- oil cooler
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