[Thornbury]

Hi, I have a 1987 40hp Evinrude BE40TLCUD fitted to my recently purchased dory. Before it's first outing I tested it on the drive using ear muffs and hosepipe and everything seemed fine. In open water however, the engine didn't want to idle with the hood on; it was fine on the drive with the hood in place. I carried on the test without the hood and all seemed fine but smokey. The smoke appears to be coming from under the hood (if in place) and not just being exhausted through the prop. The mix is correct as the VRO is disconnected and I premixed the fuel at 50:1. The engine also seems very noisy, even for a 2 stroke. Do you think it could be the exhaust leaking around the engine that is made worse by backpressure in open water rather than the smoother less smokey running with muffs and hose? Would this cause poor running/stalling? After a high speed test the alarm sounded and the engine died immediately and refused to restart, had to limp back on a small standby engine. Tested fine again with the muffs on the drive. There is always plenty of water out of the tell-tale but I need to investigate this further; or could this be connected to my theory of leaking exhaust or even head gasket?

[tashasdaddy]

was the alarm constant, if so it was overheating. just because you have tale tell stream, does not mean the thermostat is opening an cooling the power head. the symptom of running badly with cover on is usually, gasket between power head, and mid section, leaking exhaust back up into the cover. it has little oxygen, required for combustion.

[Thornbury]

Thanks for the quick reply, it looks like a partial strip down is required then to change the gasket. I did suspect as much but was hoping I had missed something that may have been a little simpler. Would this explain the difference between using muffs and a positive pressure hose feed compared to being in open water and relying on the water pump and the associated back pressure in the exhaust system? Yes the alarm was constant, research I've done led me to believe it indicated overheating but the good water flow puzzled me. Your explanation of the thermostat not opening and therefore not allowing the water around the head makes perfect sense and I'll change it.