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Coating on cylinder walls?

H

HeyJohnny

New member
G'Day

Just saying hi with a first time post from me in Qld, Australia.
I had some trouble with a chunk of leaf valve that broke off and made its way
through the bore of my 95' Evinrude 15hp. I have it in pieces and want to
have it bored to maybe .020 oversize. After talking to my neighbour about it he said
that it might have some sort of electro plating in the sleeve that will
have to be replaced. Since he's more of a bike mechanic I thought
it would be better to ask people that know about boat engines if it is true.
Finally I was wondering if anybody have ideas on what the pressure should be in each cylinder after final assembly? I know it should be very close between the two.

Cheers Johnny
 
As long as the scoring isnt too deep, 0.020" should be fine... But first check to see what pistons are currently available before the block is actually bored..
In theory you should be able to get +20 and +30 and possibly +40...
 
I mentioned in the original message that a piece of leaf valve caused the damage to the cylinder. I have noticed that the valve plate has some damage right on the edge of the opening where the offending valve used to shut. How bad is this as you have to really look carefully to see the damage to this valve opening. I can only guess that the seal would have to be perfect.
 
If the +20 isnt big enough... Pro Marine make +30 and also +40. Part no. are 8120P, 8130P, and 8140P...
 
The machine shop wants to have the new pistons before boring the block...I said to them that the standard bore for this model is 2.375 and that the
finished bore needs to be 2.395 for 0.020 over and 2.405 for 0.030 over. Is this really all the info needed for them to bore the block without the pistons?
 
Some machine shops like to have the pistons on hand before they bore... But really if they bore it to the correct finished bore size there wont be a problem... My machine shop has never asked for a piston and they have never got it wrong...
 
tonyaus said:
Some machine shops like to have the pistons on hand before they bore... But really if they bore it to the correct finished bore size there wont be a problem... My machine shop has never asked for a piston and they have never got it wrong...
Click to expand...

Very helpfull mate, spoke to another shop and they said no worries. Rang them this morning and picking it up later today.
 
Does anybody know if the ring end gap specifications still apply to .020 oversized rings. Will be getting the parts to rebuild this engine soon and want to make sure I gap the rings properly.
 
Same specifications apply.-----------------Likely no need to do any modification of ring end gaps.-----This stuff is well made these days.
 
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