Seems like only a few days ago that I posted that, but already I can’t find it. So here is a re-run:
From around 1950 thru 1967 the crankcase puddle drains led to a channel and passage in the front of the casting and were dumped into the exhaust housing and lake. And the motors ran very well. Then came the years of “smog control” in cars and they ran like crap. Outboards didn’t escape either. A mad rush was made to eliminate emissions into the water, and some of them ran like crap also.
OK, here is the plan.
Starting 1968 part of the drainage system was eliminated, and what was left was routed through a hose to a fitting in lower bypass cover….actually one of the bypass cover bolts which was a combo bolt and fitting. From there it went through the casting and into the exhaust area, where the heat was supposed to evaporate and "smoke off" some of the fuel & oil. The rest still went out the exhaust into the lake.
Starting 1973? They re-routed it into a fitting in the upper bypass cover so it would be drawn into the cylinder and burned. You know how well that worked out. Result was poor idle because the upper cylinder ran richer then the lower one, making carburetor mixture adjustment difficult or nearly impossible. Lean it out enough to prevent the rich upper cylinder, and the lower one lean sneezed.
What we are going to do is revert your motor back to the 1968 system. It won’t run as well as the pre-1968 models, but the only way to do that is with a pre-1968 powerhead. To do this you will need a 3/32" aircraft (extra long) drill bit and a special fitting and gasket washer. The fitting is part number 315230 and washer is 303630. Try a dealer. A decent hardware store should have the drill bit.
Remove the bolt from the lower front corner of the lower bypass cover. Before you go any further, screw your fitting and gasket into the hole and attach a piece of hose. Can you blow through it? If you can, it already is drilled, so do NOT continue with the drilling step in the next paragraph. But if you cannot blow through it, it needs to be drilled, so remove the fitting and continue.
What we are going to do is drill a 3/32" hole through the bottom of the existing bolt hole, into the exhaust area for the drainage to flow through. Yes, I know, you can’t get a clear shot at that with the drill. That’s what the aircraft drill bit is for. Eyeball-align the bit as close as you can with the bolt hole and drill right through the lower motor cover pan, enter the bolt hole, and carefully drill through the bottom of the hole till it breaks through inside. You should be able to tell when it hits "air" inside. Then STOP drilling. You don’t want to drill on through the next wall.
Screw the combo fitting into the bolt hole and attach the drain hose. You are done.
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