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Ring end gap tolerance?

H

HeyJohnny

New member
I just got all my parts today for a complete powerhead rebuild of an Evinrude 15hp 1996. The block was bored 0.020 oversize from 2.375 to 2.395".
First thing I did was to check the end gap on the rings and here is what I found.

Shop Manual specify: Min:0.005 Max:0.015 for a standard bore.
Ring Set 1: 0.13 top ring - 0.17 bottom ring
Ring Set 2: 0.15 top ring - 0.17 bottom ring

These measurements were all taken in the same bore and at the same deph for comparisson. My conclusion is that both bottom rings seem to have to big a gap and both top rings are within spec but slightly different sizes even though it is almost at the upper limits. The company who did the work on the block assured me that the cylinders are exactly 2.395" honed and finished. What is the thinking amongst the members on Workshop Manual specs and whether they hold true for engines that is bored oversize like mine. I don't have any equipment to meassure the cylinders precisely myself but the new pistons fit into the bores very snug with very little gap. All parts are genuine Evinrude.

Do I now have issues because the bottom rings are already slightly over the manufacturers specs? Is the reason for the measurements being at the upper limits and just over, that the sleeves are bored bigger than what I specified they must be? :confused: Will this engine work properly with these meassurements?
 
G'Day

I have put this motor back together and this is the problem I have...The motor starts extremely easy(2nd pull from cold, first pull when hot). It idles beatifully and smooth. It is smoking heaps because I am running a 25/1 fuel and oil mix as per workshop manual break in procedure. When I took it for its first water test yesterday it again started very easilly and idles great but will not get up to more than half power when under load. It refs up normal in neutral.

There is no hesitation when you open the throttle, its more like a gradual build up to half power. There is no explosive power like it used to have in the days before the piece of reed valve went through the cylinder. After discovering this I took it home, flushed it and did some testing...

Cylinder 1 = 120psi
Cylinder 2 = 117psi
Other information can be found in the post above

This morning when I looked at it again I noticed some oil is leaking from the very bottom, at the front part of the prop where it attatches to the gearbox. First I thought it was gearbox oil but on closer inspection I found that it was 2 stroke oil. Is this normal for 2 stroke to be leaking out from the exhaust when running double oil mix for break in and would this have something to do with the fact that it doesn't have any top end power under load? Everything appears to be normal except for the fact that it is gutless under load. Any ideas would be appreciated.
 
I can't help with the power issue, but yes even 50:1 and trolling you will see that oil leaking.
That is normal especially since you are running 25:1 temporarily.
 
Check to be sure that both cylinders are firing. Your symptoms of no power AND oil leaking from prop tell me that one cyl is dead, and the unburned fuel is exiting at the prop.
Use an inductive timing light, look into it when running, I bet you see a difference between cylinders.
 
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