Recirculation on a 3-cyl

I have a 70 hp evinrude from 1987. Can anyone describe to me how the recirculation of fuel/oil works on the 3-cyl's? It's obviously not the same as on V-engines with hoses and check valves.

Recirculation on bottom crank: A small path is drilled/routed through the bottom crank bearing into the crank cover and manifold plate and through a hose out to the bottom og the air box. Which way does the fuel/oil go? Does the crank suck up the fuel collected in the bottom of the air box or is it the othe way?

Recirculation on top crank: A larger path is drilled/cast into the top crank bearing and into the crank cover and ends with a routing on the inside of the manifold plate just above (but outside) the top reed box. My guess is that on piston downward motion a small part of the fuel oil should be pressed through the top crank (assuring flow and thereby lubrication) and squirted out just outside the reed box where it can be sucked in through the reed again.

The reason I'm wondering is that I'm beyond all doubt that I have to much crank pressure and fuel/oil mix esacping through the top recirculation. This makes the engine run terrible on rpm's lower than about 1500. Have cleaned carbs, link & sync, set ignition, replaced reeds (composite) and so on but the top cyl just won't run OK below 1500 rpm. This makes the idle performanced very unstable and trolling/dock manouvering a nightmare. Se my other thread on this:
http://forums.iboats.com/showthread.php?t=331740&highlight=blowback

Engine block is rebored to +,030" with new pistons, rings, bearings, gaskets etc. Have not done more than about 10 hours since. Reason for this was a top cylinder/piston meltdown (previous owner). I now wonder if this poor idleing condition could have caused the first breakdown...

Re: Recirculation on a 3-cyl

How have you come to this conclusion have you tried a differnet carb, swapped the coils around from cylinder to cyinder , I find it hard to believe the issue is to do with crank case pressure, more likely reed valves , carb or ignition. If it is runnign like a dog on low rpms it sound as it the idle jet is blocked somewhere in the orrfices , do you have slow speed needles ? does it make any differance? a bad carb is most likely the cause of the first fail and might be the second if your not carefull.

rgds
bob

Re: Recirculation on a 3-cyl

Take a can of aerosial fogging oil and squirt in upper carb at idle and see if cylinder picks up. If it does you have a low speed fuel problem, most likely low speed jet. I might be wrong, but I don't think that there is actually a recirculation system on your engine, just a means to route and burn off excess oil/fuel mixture.