Ok ready to do some trouble shooting ?
Got a manual ? You will have a private message in a minute after i post this.
First remove the hose at the t-stat housing that comes in from the transom, put water to the drive and start the motor make sure the drive is fully down, and hold the hose straight up, you want to see if you got good water to the t-stat understand, you need to see water shooting up 8-10" 2-3 seconds shut off the motor.
Say you got good water to the t-stat then open the t-stat housing and replace the t-stat or test it in boiling water to see if it opens all the way. Maybe the pieces are clogging up the t-stat housing.
Say you do not have good water at the t-stat then the pieces of the old impeller is blocking the fitting that enters thru the transom to the long hose that runs to the t-stat.
Understand ?
Now you want to know what to do ? And your idiot mechanic didn't understand stringers or how they work, did he ?
Your going to have to backflush the long hose that enters the t-stat.
I'm typing with 2 fingers and will take me about 20 minutes to type this hope you apreciate this.
Crank the bow of the boat down, place a flat that is the very piece of wood under the skeg,
it is the fin on the bottom of the drive , drive fully down.
Now crank the bow up till the skeg touchs the wood. Bow look at the rubber bumpers pry them off gently, and mark exactly how they came off, i use red nail polish and run a line on the side before removal.
See the caps on the trunion mark them they have to go back on exactly how they came off the same side capiche?
Remove them, see the bushing on both sides, Ok now you need a helper to crank the bow up another 1-2 inch's and the drive will be free drag the drive over 6 inch's port " left "
And tie it to the boat, DO NOT PULL ON THE CABLE YOU F THAT CABLE UP WILL BE 600 DOLLARS AND A WORLD OF HURT REPLACING IT, capiche?
Now backflush the long hose and see if the pieces come out the intermediate.
Post back at that point with the drive off and keep us informed, we will go from there i have a feeling this ain't over yet but with our help you will get thru this if you listen, don;t listen then it's your fault not ours.