According to the TCDS, you have a choice of three props:
1. SENSENICH 74DM6058
twobladed,
fixed pitched
Maximum diameter 1880 mm [74 in]
2. SENSENICH 74DM6056
twobladed,
fixed pitched
Maximum diameter 1880 mm [74 in]
3. SENSENICH 74DM6054
twobladed,
fixed pitched
Maximum diameter 1880 mm [74 in]
For other propeller limits refer to AFM
https://easa.europa.eu/system/files/...2-08012007.pdf
I'm guessing you're not getting 150hp out of the engine. According to that TCDS, the gross wt is 1874 lbs?? Gross on my 150hp C172 is 2300 lbs. It ought to climb just fine on 150hp, unless you're trailing a drogue chute? A good mechanic needs to go over everything, intake, ignition, carb, and exhaust to find the problem. I climbed at 700fpm today in 90 deg air solo.