"on compression test, yeah, in
"on compression test, yeah, in theory, you should have engine warmed up. in theory, you should also take engine to sea level (i live at 4000'). in many cases, neither one is practical so you just run the test as best you can and interpret figures. honestly, you can probably tell enough to know whether it will run just by holding finger over plug hole while friend pulls rope or cranks it with electric start. you'll get a lower than normal reading if engine is cold (blowby due to cylinders & pistons not having expanded to operating tolerances), but i'd say if you get anything over abt 85-90 psi cold, go ahead and try to run it....i'm guessing this would equate to abt 105-110 warm. since 2 stroke has no valves, main source of compression leakage will usually be piston rings....after you run test, squirt some oil into plug holes and re-run test....if you get big improvement, this indicates your rings aren't sealing well. significant differences between cylinders are Not Good and often indicate internal issues. even if you need to do pistons/rings, last time i priced em for the 40, they were abt $65 each; multiply that x3 for the 65. if you know how to do work yourself (or are willing to learn...many local community colleges in coastal areas have intro to OB maint courses), you could nearly rebuild one for cost of the annual service at dealer on a modern 65.
there really isn't much to one of these old motors....2 stroke engine designed to run at constant RPM coupled to prop, with dog clutch that moves gear cluster back & forth on propellor shaft to engage either the F or R pinion....not too much to go wrong as long as you have compression, and these engines are pretty modular and many parts can be swapped between models. the stuff i replaced on the 40hp pretty much eliminated most of the sources of stranding....carry a spare fuel line/primer bulb and a pull cord for starting if electric start dies, and you should mostly always make it home. OTOH, i once had to paddle in from over a mile offshore when the CDI 'power pack" on my late-80s 'Rude died without warning, as they apparently have a bad habit of doing, esp. when run on crappy fuel..... "appropriate technology" for OBs is often old n crude, but it works........only real downside is they suck fuel & spew much of it into environment"
