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Honda 5HP BF5A - Loses Power and Runs Erratically when Engine Cover Put On

martini

New member
Hi - I've got a very unusual problem with a Honda 5HP outboard. Without the engine cowling cover on, the engine runs fine under all conditions. Whenever the engine cover is put on, the engine loses power, and cuts out under load. Initially I thought it was an air problem or something on the cowling blockiing a cable or pipe on the engine but I couldn't find anything. I discoverd that if you cover the plastic black cowling over the starter flywheel the same symptoms show themselves. It's as if blocking out light from the flywheel area causes the engine to malfuction and lose power. Is there some kind of sensor mounted as part of the flywheel that has built in illumination that may have failed? I've heard that some outboards use a marker and optical sensor for timing adjustment. I thought that if such a sensor partially failed it might explain the problem. Would welcome suggestions about fixing this problem. - Many thanks.
 
You have an exhaust leak and trapping the carbon monoxide in with the cowl and suffocating the engine.

Thank you. That sounds like a plausible cause. Have you seen this problem before? What's the best way of chasing down/fixing the problem? I can't see anyting unusual but I'm guessing it may not be obvious what the source of the problem is.

Best wishes,

Martin..
 
This issue is more common than you think on older motors.
The exhaust can only be inspected by removing the power head, there is a casting between the power head and the top of the extension housing which corroded or maybe just a leaking gasket. It's a relatively simple job although a manual would be useful
 
This issue is more common than you think on older motors.
The exhaust can only be inspected by removing the power head, there is a casting between the power head and the top of the extension housing which corroded or maybe just a leaking gasket. It's a relatively simple job although a manual would be useful

Many thanks. That's very helpful. Sadly though, not that old or hard worked motor. I'll let you know how I get on.
 
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