2004 F60 hard start when warm

"I have a 2004 F60 that starts

"I have a 2004 F60 that starts right up when cold. Idles and runs great. After the engine is warmed, the engine just turns over and the engine doesn't even try to fire. I have tried to pump the accelerator a few times and then turn the key with not luck. The only way I can get the warm engine to start is to hold the accelerator about half way open and turn the key to start. The engine fires right up with an rpm surge due to the open throttle. I have to hold the throttle open for a few seconds to keep it from stalling and then slowly bring it back down to idle. It then idles and runs great.
If I turn the warm motor off and then try to restart it within 5-6 minutes, it will sometimes try to fire up, but not always. If the motor has been off for any longer than that, it doesn't try to fire.
I took the boat to a Yamaha dealer twice last month with this problem and still have not had it fixed. They did the yearly service first, and installed a new fuel/water separator. Then they cleaned and readjusted the carbs, checked for spark, and checked/tested the fuel system. Fuel system and spark checked out ok, but they said there was some trash in the carbs. After all this, the warm starting problem is still there. The service manager said he hasn't run into anything like this before. Any ideas as what the problem might be?"

Your not choking the engine wh

Your not choking the engine when it is warm are you? That could cause it 2 flood.

"Did the dealer warm it up and

"Did the dealer warm it up and then try to troubleshoot the problem.

I have seen ignition components develop a crack etc that only creates a problem when hot. The engine heats up the windings (copper), they expand and lose continuity.

You will get great spark on a cold motor, but heat it up and the problem surfaces.

You can test at home if you have a timing light. Just hold a blow drier on the flywheel until it's almost too hot to touch and then see if the spark is ok, or run the engine, shut her down and retest..."

"There is no manual choke. I

"There is no manual choke. I don't think it's flooding anyway. It doesn't sputter when it does fire up, and it doesn't smoke as if it's overfueling.
The dealer did run the motor to warm it up and experienced the warm starting problem. They did check for spark output, and the ignition system checked good.
This is a hard starting problem when the motor is warm, after I have been drift fishing for a while. Once I get it fired up, it runs normal.
The dealer has talked with Yamaha about this problem, and even has Yamaha puzzled! Yamaha wanted to know what brand of gas I buy, specifically wanted to know if I've ever purchased gas from a Wal-Mart, and also wanted to know if I could possibly still have the winter blend of gas in the tank. I told the dealer that I usually go to Shell or Sunoco because they're near my house, and because I live in Central Florida, I boat and fish year round...the winter blend was burned up long ago!
Sooooo, we're still digging.
Please keep the suggestions coming!"