I have a 2000 MERCURY 200EFI. I had a new powerhead put in last summer and it's been a piece of junk ever since. The mechanic over oiled the fuel tanks for the brake-in period and plugs would foul every 5 min of run time. After finally getting past the break-in period the engine would run great at full throttle. It did however bog down and take awhile to get on plane. Then after stopping and starting a few times, I would start the engine and it would idle then put it in gear it would die and not start again. I would swap sparkplugs the first few times it did this and it would go again. The last time it did this the plugs didn't work, then I notice I couldn't get he bulb to prime. After getting towed in and getting home 2hours later I primed the bulb and it firmed up and the engine fired right up. Any thoughts on what might be the problem with this moneypit of mine would be appreciated. Can't trust the mechanic I took it to, so would like a few ideas before I take it to someone else.... THANKS.