3 questions about powerhead disassembly

[cenkaetaya]

Hi, i took apart the powerhead of a 40HP 1990' Evinrude.

I had a few questions:


1 - I noticed each side of the crank shaft had holes on the shaft and cover. I made a circles in red around them. I am trying to understand what these holes are for and why each side has them. They seem like some sort of vent / pressure release vents. If anyone can explain why the powerhead cover has a holes around these two end parts that would be awesome.

2 - why does the piston have the little piece of metal separate from the rest of the o-ring?

Thanks

 

[Chinewalker]

There are passages machined into the block and crankcase to allow circulation of the fuel/oil mix into the various bearings. They also help with recirculation of puddled fuel, as some motors can get excessive fuel collection in low spots during long idling.

The other pic shows a broken ring, not uncommon with the scuffing evident on the piston skirt.

 

[racerone]

The wee pins are there to keep piston rings in place.-----You would not want the ring gap where the ports are

 

[Faztbullet]

Make sure you bore that cylinder at least .020....

 

[cenkaetaya]

Thanks guys, I may have a few more questions. I took this apart as I am reverse engineering it since i have 3x of these motors and understand every part of it.

Do you know why the top piston ring would have the little piece of metal, and the bottom ring does not?

Also the bore .020 was a joke right?

Thanks

 

[F_R]

Ring is broken into pieces.

 

[Scott Danforth]

Also the bore .020 was a joke right?

Thanks

no, you need new pistons, new rings, and need to bore and hone the cylinders. it will take about 0.020" to clean up the bores based on what the cylinders look like

 

[Silvertip]

Seriously -- you weren't considering putting the engine back together with these seruosly danaged parts?