Mercury 15hp 4 stroke hard starting

"I have a 2003 Mercury 15 hp 4

"I have a 2003 Mercury 15 hp 4 stroke tiller with "pull start". When cold, the engine will start on the first or second pull and run all day, as long as it is not turned off. If it is shut off after running around the lake it will not start. It will not even "sputter" or "cough" no matter how much you pull the rip cord. It is completely lifeless. In the past you could let the engine sit for 15 minutes or so and it would start again easily. Now the problem seems to have degraded as I could not get it started at the lake today after waiting > 40 minutes. It should be noted that I could not duplicate this problem while running the engine off a garden hose while in the driveway, as it would start easily every time.
Any ideas?"

"Marc, first have to determine

"Marc, first have to determine if this is an ignition or fuel problem. If you can borrow a timing light, take it out with you.

When the motor won't start, check to see if you have spark at the cylinders. Often times a break in one of the ignition windings only shows up when the motor has really heated up - the copper expands and "no continuity" is the result.

You can try and fake it out in the driveway using a blow drier to really heat up the components under the flywheel. Or it could even be a bad stop switch (which I assume is what you use to turn the engine off while on the water).

If however, you find that you still have spark when it won't start - then you will need to troubleshoot the entire fuel system. But my first guess would be that this is an ignition related issue....

One last note/question - how old are the spark plugs? I have seen bad plugs cause this condition as well. For a couple of bucks you could save yourself alot of "head scratching" (maybe)...."