retrosub
01-05-2007, 11:29 AM
I have an older Evinrude 15hp engine that's a bit too small for my 14' inflatable. It'll plane with 3 people, but only just. With fish, gear, and water in the boat, it plows. So I've been researching a replacement. From my understanding, old outboards were rated at the crank, whereas new outboards are rated at the prop.
What year did the HP on outboards start being measured at the prop? How much difference is there? I know on shaft-driven motorcycles there can be a 15-20% difference between crank horsepower and rear-wheel horsepower, is that about the same for outboards?
If the frictional losses from the driveshaft and age of the engine combine for a 20% difference in power, by today's standards, I have a 12hp engine. No wonder I feel so underpowered.
What year did the HP on outboards start being measured at the prop? How much difference is there? I know on shaft-driven motorcycles there can be a 15-20% difference between crank horsepower and rear-wheel horsepower, is that about the same for outboards?
If the frictional losses from the driveshaft and age of the engine combine for a 20% difference in power, by today's standards, I have a 12hp engine. No wonder I feel so underpowered.