Timing Question

[1979 Quartermasters]

I have a 1995 5.7 Mercruiser Thunderbolt Alpha I Gen II. I just had the carb rebuilt and its running way better. I beleive the tec that did the carb said it was a Carter. He also told me to advance the timing 5 deg. Is a good idea? Currently I cannot get wot as it stops pulling at 4100 rpm. Before I had the carb done I was getting 4500 rpm, But when I came off the power, it would stumble all over its self and then stall and be really hard to start. That problem has be solved. I have a 5 blade SS, 21p prop.

Thanks for any sugestions

Ken