1978 85hp evinrude stops suddenly

[bigslick]

This motor runs great for about 10 minutes. No spitting or sputtering. Then it just shuts off like you turned the key off. If you let it set for a hour or so it will start again but it wont run long. Any ideas to pinpoint the problem would be most helpful and greatly appreciated.

 

[jtexas]

Re: 1978 85hp evinrude stops suddenly

Fuel line holding pressure?
Tank vent open and clear?
Any other symptoms? Cold start, warm start, acceleration?
Been like this since you got it?
Have you done any recent maintenance?
What's the compression on this motor?

 

[bigslick]

Re: 1978 85hp evinrude stops suddenly

I recently replaced steering cable and plugs. The motor had been running fine.I got about 20 good hours on it this season. It is getting fuel even when i have no start . It still runs good right up to the moment it shuts off.

 

[jtexas]

Re: 1978 85hp evinrude stops suddenly

First, compression test.

Second, spark test (not a "spark plug" test): get an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it's not firing in the hole under heat & compression.

If you can test for spark after it quits, even better.