Logo
FULL SITE MENU

Dumb question on a 5.5 hp Evinrude...

Rook66

Rook66

Regular Contributor
In the diagram below for a 1957, 5.5 hp, Evinrude item 15 is called an "oil drain valve plate" and item 16 is called an "oil drain leaf valve".

My question is what do these things do? I really don't understand what they're for? It appears they're just 2 brass rectangle shaped pieces of metal stacked on top of the other, the one in front being a little thicker than the other one, and they're held on by a single screw in the middle. There's a couple of holes that they cover, one at each end. It would appear they flutter from vacuum? What oil are they draining and where does it go? Is it excess oil from the gas mixture?

I managed to damage item 15 when taking the intake manifold off of mine and I've ordered another one.

7QhtD9D.gif
 
They pick up any excess oil that has built up in the crankcase and run it back through the intake manifold. They're called recirt valves.
 
Last edited:
Think of it this way. An atomized fuel/oil/air mixture is going through the crankcase. Some of those fine droplets of fuel fall out like rain (gravity, y'know) and collect in a puddle in the bottom chambers of the crankcase. The leaf valves drain that puddle away.

Actually, on the 5.5 the drainage is dumped overboard, but don't tell anybody. Newer models attempted recirculation for environmental concerns. But the older system ran better.
 
Back
Top