1992 Fast Strike 150

This is on my Dads boat that I use occasionally and I dont have the engine serial number but am frustrated with the problem.

The boat was running great for the whole 2010 season and the fuel lines were replaced from the engine to fuel tank with ethanol safe lines during this season. My Dad took it to the shop over the winter for a tune up and to have the lower unit serviced. The 2011 season the boat is smoking heavy on cold start up and more than before on a warm start. It also will run very well cold but if you get the engine warm turn it off for a while and fish it then becomes problematic. When trying to run with a warm engine that was sitting for about 15 minutes or more, the engine tries to stall out when giving it power. The only way to get the boat up past 1000rpm's when it starts this is to choke it a couple of times as your giving it throttle. On the top end the motor has missed a beat it still pushes the boat like before. He took it to a different mechanic this season to fix this problem and all they did was change the plugs. We have not water tested it but I'm not convinced.

Anyone have any thoughts or similar experiences?

How old is the fuel? I added Star-Tron ethanol fuel treatment and my smoke problem was cured. The boat idled well once again and very little smoke. My fuel was a few months old and probably had some phase seperation beginning.
If you are running good on the top end but rough idle and mid, those circuits may be gumming up. Get some Berryman carb cleaner and spray with the tube into the air orifices on the front of the carbs. (The little brass jets). This will blow some fuel out the carb overflow vents so it can be a little messy. Let it sit in the carbs overnight. Spray again the next day, pump up the carbs with fuel and then run it. See if this clears the circuits and your low mid problems.