Warm Start Problem on 80hp Mercury

[windrunner]

Have 80hp 4cyl in line merc with a flywheel ignition (early 80s model I think). Starts cold without much trouble and runs fine. However once engine is warm and then shut down and left for a minute or two it will not start so easily and of late has not been starting at all when warm. (had to get a tow last time I used it). Engine turns over and some smoke comes out exhaust but it just won't fire up. Spark plugs are new, engine timing is spot on, except it idles about 750 and not 650 as recommended. Cooling pump seems to be working, water comes out pee hole and engine doesn't give off excessive heat. Also just renewed fuel pump diaphragm and checked fuel system for leaks. Only possible fault is with bottom cylinder spark plug which remains cleaner than others which may suggest water getting in cylinder, but I don't understand why this would not have a more adverse effect on the engine which otherwise runs fine. Any ideas as to problem and possible solution ???. Thanks.

 

[mellowyellow]

Re: Warm Start Problem on 80hp Mercury

is she flooding? does gas spill out front of carb<br />when you pump primer bulb? sounds like a stuck<br />float to me... but that's a guess.<br />try tapping on the side of the fill bowl when it<br />happens to un-stick float.<br />may be time to install new carb kit if you haven't<br />already, but they are notorious for sticking.<br />good luck,<br />M.Y.

 

[windrunner]

Re: Warm Start Problem on 80hp Mercury

Yes there is some fuel overflowing out the carb vent from time to time and also if you pump up the fuel bubble real hard. A carb rebuild was next on my list of jobs but maybe you could explain exactly why this prevents the engine starting at normal operating temperature.

 

[mellowyellow]

Re: Warm Start Problem on 80hp Mercury

don't know why it only happens certain times, but<br />it sure sounds like a sticky float.

 

[jim dozier]

Re: Warm Start Problem on 80hp Mercury

When the engine is cold, it requires a richer mixture and a little excess from a leaking float valve may help or at least not hurt the cranking. When the engine is warm it requires the "running" mixture which is now too rich because of the puddling gas from the stuck open float. Also, when cold the fuel pump probably has not had much of an opportunity to puddle much gas but after its been running the pressure is enough to spew gas into the carb throats through the leaky or stuck open float valve.