boat dies when put in fwd or reverse

Our 1980 Ski Nautique let us down this weekend.   We are just now getting it out on the water for the first time this year.  I should start out by saying I have limited mechanical know how.  I changed the oil, replaced the fuel/water separator, replaced the impeller.  It ran like a dream in the driveway.  Idled perfect, no issues.  

We filled up 100% gas and went to Nik-a-Jak lake to get our first run in this year.  Idled fine on the trailer and I let it warm up like I always have.  I could not keep it from dying when I put it in forward or reverse.  In the past, I've had to rev it up some, push the button in and then "goose it" into gear rather than easing it into forward or reverse.  That didn't work at all.  

After clogging up the ramp and the dock for about an hour, I gave up and put it back on the trailer to go home defeated.  I've reviewed some previous threads on here that seem to discuss the same problem.  The thing of it is, like I said, I've got a limited skill set when it comes to mechanics.  I might as well own that rather than having you guys think I understand all the wisdom that is so often shared on here.  I'm grateful for that.  

I think what I'm really looking for is a good boat mechanic.  I've tried hot rod shops, the typical marina shops around here, and a few shade tree guys.  What do i need to look for in a mechanic for this boat and do any of you guys live nearby and have any recommendations.  

If you guys recommend things I should check out myself, I am thrilled to do so and learn.  I've searched YouTube and found a few videos but none that address this particular model of boat.  As always, I'm grateful for the help that is so generously shared here and if you had a lead on a good mechanic, that would be amazing.  We are in Chattanooga, Tn and I'm willing to drive a bit to get the boat running reliably.  There isn't much worse, in my opinion, than having two kids sweating to death in a hot boat while I try to stare at the motor until the gods of the water send me a sign....

Have a good one.  

k

k