Re: Why don't older 2 stroke outboards require routine rebuilds?
Compare apples to apples, not oranges, meaning you are comparing 4-stroke displacement to 2-stroke displacement...
In my example I compared 2-stokes of approximately equall cubic volume and pointed out how the road going engines are rated at much higher horsepower. This is because you do not opperate a vehicle on the road at full throttle for most of the time.
When you do this type of comparison, it is quite clear that the outboard engines have much lower rated horsepower per cubic inch of displacement than a road going 2-stroke. Additionally, if you look at my 9.9 carb and compare it to my RZ250 engine, it becomes even more obvious: the RZ has two 26 mm carbs compared to the single 20 mm bore carb on the 9.9.
Consider that my 1969 McCulloch MC-101 (125cc) Kart engine puts out 12hp on gasoline, 18hp on alky, and it makes the 216cc Johnson 9.9 look like its loafing on the job!
Look at 4-stroke small outboards, they are roughly twice the displacement as their 2-stroke counterparts, so it's not a good comparison. Now look at this comparison: My 5.0 302 Mustang HO puts out 325hp, but the same engine prepared by Waukesau in my 18 foot tri-hull is only rated at 165hp, and has a small 2 barrel Holly, it's basically a restricted version of the same engine for marine use.
Thus to be clear, so I'm not missunderstood, if you have two engines of the same type, of aproximately the same displacment, the marine version will put out about half of what the road going version, because the marine version is rated for continous duty, not intermittant duty.
