i wish there was a mercury mechanic that didn't guess about whats wrong with the my outboard. all i get is weeelll it might be this... it could be that.... it sounds like it.... welll try this.... wth !!! how bought a answer and stand behind your diagnosis and if you put a part on or do something that doesn't fix it after they say that they no what the problem is then then they charge you for the part or the service even thou it didn't fix the problem!!! seriously what do they go to school for??? just to no how to make the tools work and take it apart and putting it back together how bought learning how to fix it!!! i don't mind spending the money on parts or labor if what there doing fixes the problem!!! i dont like paying for miss diagnosis..... my motor is 1999 225optimax i have a idle start problem it will start right up and quit after a minute i have to use the hotfoot afterword to get it started hold it about quarter throttle and slowly lift up on it to get it running until it warms up a little and after a run down the lake you can shut it off and it will start right back up but if you let it sit for to long you have to use the hotfoot to get it started. the mechanic and mercury says it sounds like the fuel injectors are dirty because if you unplug the thermostat sensor it will start fine and idle they said to try dumping quikclean in the fuel filter which i did several times and didn't help now before i send out my air and fuel injectors and fuel rail to get cleaned for 600 bucks + anybody got any idea's

No ideas, but any 99 Optimax that's still running is indeed special. You should have blown at least one powerhead by now, you lucky dude. I'd for sure go to a different mechanic for starters.

Unfortunately this sounds familiar to an issue I had with 2000 Optimax 225hp.

Turns out the issue was the diaphragms in the fuel system had deteriorated, my issue got way worse when one got a hole in it. The issue was causing fuel to enter where only air should be so when the fuel was mixed it was getting the normal amount of fuel plus whatever was in the air system. The mechanic figured this out when he went to check the air pressure in the system and fuel shot out.