same as a yamaha c30, well the powerhead is. I can't speak for the foot/leg/clamps/etc because I did not really compare them.
rougher running, noisy, a bit thirsty but pretty good old motors--so long as it's been maintained. With that said, keep in mind it's an old motor.
They put the "C" in front of some of the horsepower ratings for model numbers (C25, C30, C40, C60, etc). C I think was for "commercial", I called them "cheap" because they were less expensive than the pro 40, etc, for a reason. No frills. Noisy, thirsty, premix only, little rough running but rarely saw one hurt that wasn't the result of abuse/neglect. Only one I ever went into was a C30, water pump died and they kept running it, seized it, let it cool, fired it up and kept going. Repeat, rinse. Had 50 lb compression on the bottom cylinder and 90 on the top, destroyed but again, abuse/neglect deal
for a while out here the duck hunters were buying them. Lighter weight, and the C25 is the same powerhead as a C30 (yamaha) and they were modding them, some guys were squeaking 40hp or so out of them. Don't ask me how, I ain't up on mods. Legal for 25hp restricted waters, as they were stickered as 25's, and the serial number tag matched. Noisy things! They've kinda fallen out in teh past few years, so nowadays you can get the C30 and the mariner 30 for pennies because the 4 stroke stuff is really getting popular; and not many even want the old 2 stroke stuff now (unless they're die hards or racing) hence the reason I call them "cheap"
IIRC they didn't have overheat alarms (remember..no frills). Can't say whether Mercury/Mariner put the alarm on their version or not, I don't think so but it's been a couple decades since I've been around mariner or mercury
