Piston Gap on Cylinders

[FillupD]

What, if any is the accepted lateral movement of a piston in relation to the cylinder wall? For example, I have a 73 50hp evinrude and with the head removed, and while putting lateral pressure on the piston top, the piston will move (the rings stay stationary) approx. .020 or more. I can kind of jiggle the piston in the cylinder wall and seems to move freely to the point of where I can move it rapidly and an hear a kind of clinking sound as it hits the cylinder wall sides.
If I were to guess, this is an extremely worn motor, or is it supposed to move laterally in the cylinder?
Any opinions would be appreciated.

 

[micel]

Re: Piston Gap on Cylinders

It sounds as if thats pretty loose,Id do a compression check and if they are even and above 80lbs use it.The only way to correct this would be to rebore and new pistons $$ .With the cowl off it will be considerably louder than a tight engine.The.02 measurement is a tight piston to cylinder wall gap.

 

[FillupD]

Re: Piston Gap on Cylinders

When the head was on the compression was good, 130 or so if I remember correctly. There is a guy that looked at it and said that the pistons were probably allowing blowby when it was under load so it wouldn't get up to proper RPM on the water (which it will not, as as load increase the RPM's decrease). And there should be some crosshairs on the walls but these are smooth. But he did say he didn't really know too much about these type on engines so I though I would see what the experts had to say.
I may be able to get a good motor a couple of years newer and switch it out for probably the same price of rebuilding. ~750.00

 

[jonesg]

Re: Piston Gap on Cylinders

When the head was on the compression was good, 130 or so if I remember correctly.

there is no reason to remove the heads if compression is 130psi.!

I think you're looking in the wrong place.

Put the head back on, remove cowl and try advancing the timing mechanism by hand when it starts to bog, then try pumping the bulb or chocking it slightly to increase fuel flow, thats where I believe you'll find the problem is.