Corrosion proofing on Reims-built arcraft was actually an optional extra but nearly all were painted on the inside. Only snag was that 'assemblies' were painted rather than individual components, so the skin faying surfaces were left bare metal. I have pictures of a very bent FA152 that demonstrated it where the skin joints failed. For my sins I've maintained a couple of fleets of 150s (including FRAs) and 152s for flying schools.
O-235 was an excellent engine but not the best starter - tight plug gaps and running the engines at 1700 rpm prior to shut down kept the plugs cleaned and that helped (as well as both mags being impulse type).
O-240 starter clutches were a very expensive and problematic item. B&C starter cured that problem! You can always spot an FRA150 by the blisters at the front of the top cowl over the cylinders - although some FRAs were re-engined with O-200s as the O-240s could be more expensive to maintain and crankshafts and other parts became extremely rare..
The 150M had the same pre-select flaps as the 152.
PS I would have liked an FA152 Sparrowhawk that had a 125 hp O-235 but apparently in the field, the engine didn't survive well although it was fine on the Lycoming test bed.
Last edited by smarthawke; 8th Apr 2020 at 09:57.