Originally Posted By: CT8
Why the apples and oranges comparison?
Ok, you asked for it. Here's the long version.
I have a '78 Evinrude 15hp, the one in my sig. Rolled the dice on it a few years ago, and it's probably toast at this point...been chasing problems and has left me SOL on Lake Erie too many times at this point. My marine mechanic also agrees it's time to move on.
The older two stroke outboards...the 8, 9.9, and 15hp blocks were all the same in many cases, and the same weight...about 80lbs. This weight is pretty much the max for me as far as pulling the outboard off and on the transom on a regular basis like I have to do.
So I'm looking at replacement. There are a small handful of older outboard options. 2 that I looked at (15hp) and did compression checks on were about 85%. So was the one I'm bailing on.
In the newer 4 strokes, the 9.9hp is a smaller engine than the 15hp, and they weigh about 81lbs and 97lbs respectively. The 15hp 4 stroke is out in this case. Why a new 4 stroke? The weights have come down in the last few years, and every lb counts.
When I take my wife and daughter out, the 15hp 2 stroke gets the boat on the plane. My brother's 2 stroke 9.9 struggles. So when finding a replacement, I'm right at the cusp in terms of power, so I don't want to lose any. I just can't do the 4 stroke 15hp, so I would have to do the 9.9hp 4 stroke if I go that route. And a 15hp 2 stroke if I go down that road again.
And then of course there are cost considerations. Used would be about a third of a new 4 stroke. Maybe I get a good one. Maybe I get someone's problems. Marine repair costs add up fast.
The ultimate question, which I tried to word in the OP, is will a new 9.9hp 4 stroke match the output of an older 2 stroke 15hp with what seems to be a normal decrease in compression from age/use?