Shifter help

[Hopppy]

Looking for a recommendation for someone to work on my shifter- I have a sea ray Sundance 280 with twin merc 5.7l the starboard shifts well, the port shifts blurry hard and 80% of the time stall when shifting- 

i have been battling this for a year. I have had marina lol at this multiple times, 1st they replaced lower shift cable and something in our drive- pulled upper cable and stayed there was no issues with it. Problem was not fixed- they looked at it 3 more times last season and I requested it be looked at again w/ spring commission. Maiden voyage today and problem persists. 

Looking for a good merc mechanic near Mexico oswego area. I can’t trailer this so they would have to come to me or be on water with ability to haul if needed. 

Thanks