Rated HP

[squarles]

What year did Mercury/Mariner go to prop rated HP? Would an 85 model Mariner be rated at the prop or at the crankshaft?

Thanks

[transomstand]

Pretty sure they changed in 82. At any rate, by 85 it was definetely at the prop.

[Raceman]

You do of course realize that HP ratings have more to do with marketing and relativity between engines than actual output. There have always been cases where minor upgrades made EXACTLY 10 HP difference in the output. All of the manufacturers seem to be able to find increases in exact multiples of 10.

[O/B Dude]

81 merc 225 became 82 merc 200. Exact same motor. Transomstand is correct. It was 82 that they went to propshaft hp ratings. But like raceman said, they rate them for marketing. 2.4 BP carb and EFI put out the exact same hi rpm hp. But merc rated the carb motor as 225 and the efi as 240. Same deal on the 2.5 245 carb and 260 efi. Both make about 260 propshaft hp and 280 crankshaft hp. I wish merc would make a 150 that puts out 350 hp. Speed and low insurance rates.....:D

[squarles]

I knew it was early 80's just couldn't remember what year.

I wonder if anyone has ever done a dyno test to compare rated HP vs actual?

Stephen

[O/B Dude]

I don't think it really matters on the older motors becuase they have changed so much. The early 2.4 225 had no fingerports like the 200's. Also, compared to a 2.5, the early 2.4's are dinosaurs. The late 2.4's are still a decent motor but the performance of a 2.5 is much better. Dyno tests have been done on many motors new and old. Only place I can think of now to find them are on the Land and Sea marine site. Most motors are pretty close to stated power, but whenever you have a motor thats available in carb and efi, merc always rates the efi as higher hp to help justify the added expense. :D