Compression numbers on loop charged engines can really be tricky! Of course you can use the numbers to find a dead cylinder, but hard to prove a good cylinder. Scoring, glazing or just bottle shaped around the numerous ports will misled you as to conditions of the cylinders. Add to that pressure back rings (OMC / not sure what Merc called theirs) and it is hard to determine cylinder condition with just a compression gauge. The main symptom you run into is an engine that will idle for awhile and then fade away and die. You have to choke/prime it to get it to restart. If you catch it while it is slowing down, choking/priming will keep it going. If you pull the head you will fine the cylinder walls scored, glazed or woren at the looper ports (intake). Honing the cylinders will not fix this problem! They require boring oversize with proper honing after boring.

Dan in TN
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Not aware of any derated model from Belgium or otherwise. E would be Evinrude 50hp B? (maybe Belgium) E electric start L long shaft 20" CC ’88 model S suffic could mean a lot of things. If you look in a service manual those model numbers are deciphered for you. Other letters are explained. I don’t remember any derated symbol except maybe jet engines and they don’t spell out derated HP, just the way it is!

Dan in TN

Joel
Like I say, what we are referring to is just normal wear to the cylinder wall and piston skirt, we are not talking about scuffs and scoring. In other words, pulling the head would not show problems visible to the eye. These loop scavenged engines (40-50) OMCs are more prone to cylinder and piston wear because there isn’t much metal in the port area due to the crazy sized ports leaving little metal to metal contact. The smaller amount of contact means that the remaining metal will absorb more of the wear in a shorter amount of time. The conventional cross scavenged engines have smaller port and no big "windows" on the piston skirts, resulting in less wear. The cross scavenged engines are much more tolerant of wear, even scuffing/scoring, and will run/idle pretty well even with oversized cylinders and worn piston skirts. The important thing to realize is this wear on the loop scavenged engines only has to be a couple of thousandths as well, so compression readings may still be acceptable and even.
Dan’s description of the classic signs of this wear is great, fade away idle and hard hot restart.
So, don’t worry about pulling the head on the 50hp you are interested in, do the usual compression test and other inspections. I realize you will not be able to run the engine out on the water, and running it on a hose will not show idle problems. There is another good way of recognizing this problem without even running a perspective purchase, simply look at the sync settings. An idle speed/timing screw turned all the way in (advanced) with the throttle plates held slightly open at idle is a good indicator that someone is chasing a poor idle problem that may be a powerhead problem. Needless to say, there may be legitimate carb/ignition/sync problems causing the poor idle, but seeing jacked up sync settings should make you question powerhead condition. Again, you can see this without even running the engine.
So, we didn’t mean to scare you away from the 40-50hp OMCs, they are good engines, this condition is not all that common, just something to keep in mind when looking to buy used ones. As with all outboards, look for signs that the powerhead has been apart, "new rings and a hone job" isn’t going to fix it.
So, go ahead and give that 88 50hp a look, let us know what you think and post pictures and questions if you like. D

Not as much a gamble if you are able to actually test the engine prior to purchase. By that I mean in the water and not on a hose. The engine should drop to and maintain a slow idle in gear at the static water line you will be running it at. If it does then you are golden.
That is probably the single best test of any two stroke engine and most certainly a Looper.