64' Evinrude 9.5 Outboard (Compression ?)

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Steph Boeker

Steph Boeker

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I've looked for original, official compression on my motor in Seloc & other manuals w/no luck. Can someone please tell me :
a) what is the manufactured compression of this motor ?
b) where I can find that compression # written down ?
c) what is an average window of compression for this older motor ? (i.e. 60, 70, 80, 90, ... , or 70 - 80 , 80 - 90 etc ...)
d) does the level of compression dictate the speed it can achieve ?

I mean, what is too low of a compression for it to be worthwhile to restore this motor ?
Thank you for your generous consideration,
Sincerely ........................
 
There were no published numbers for compression in any manual.
Compression numbers will sometimes vary widely depending on the gauge being used.
Compression numbers on any 2-stroke should be within 10% of each other.
For your particular engine anything in the 60# range would be an iffy motor. Oil the cylinders and check again.

 
Pappy said:
There were no published
Thanks for your timely reply. I actually have a compression of 70/70. Both cylinders are the same, but didn't know if that was high enough to be worthwhile ? I still don't know what it should be or how low it's gotten over the years. It runs. I can replace spark plugs, points and coils, tune her up and paint her. If she lasts a while and gives me 15 to 20 mph, I'd be happy.
Thanks again, sincerely ..................
Click to expand...
 
I worked on one of these for a friend a few years back and it showed on my gauge about what you’re getting. No two gauges will read the same and some motors and I suspect this is one of those do not show a true compression reading unless you use a small engine gauge.

To add to that, these engines sit for decades sometimes and stuck rings are common.

Soaking the rings in seafoam, marvel mystery oil or Ed’s red for a week or so, then running it for a bit will usually listen up the rings and give you better readings.

Having said that, if it runs run it. Depending on the boat you might see 15mph, but I don’t think you’ll see 20.
 
RaisedByWolves said:
I worked on one of these for a friend a few years back and it showed on my gauge about what you’re getting. No two gauges will read the same and some motors and I suspect this is one of those do not show a true compression reading unless you use a small engine gauge.

To add to that, these engines sit for decades sometimes and stuck rings are common.

Soaking the rings in seafoam, marvel mystery oil or Ed’s red for a week or so, then running it for a bit will usually listen up the rings and give you better readings.

Having said that, if it runs run it. Depending on the boat you might see 15mph, but I don’t think you’ll see 20.
Click to expand...
Thanks for your generous consideration. I'm working on the boat (14/52 alum. craft) right now. I'll share my findings on the motor speed when I get her out on the water.
Thanks again,
Sincerely .....................
 
Dont forget the water pump impeller at the very least and it would be wise to do a shift rod oring as well as I can just about guarantee it either is already leaking or it will be shortly.
Use OEM parts, they fit and they work.
I would use a 24:1 mixture in that engine. At the very least it will help the compression and minimize wear.
 
I believe 1964 was the year they moved up to 50 to 1....I had a 64 evinrude 18 hp that was a 50/1 mix. Being an older motor a little richer on the oil wont hurt...
 
Pappy said:
Dont forget the water pump impeller at the very least and it would be wise to do a shift rod oring as well as I can just about guarantee it either is already leaking or it will be shortly.
Use OEM parts, they fit and they work.
I would use a 24:1 mixture in that engine. At the very least it will help the compression and minimize wear.
Click to expand...
Yes, I'm actually having all the o-rings changed, the pull string gear replaced along w/ the impeller gaskets,, fuel lines, carb rebuild, .... , baically from the prop to the hood. New stickers and all. I thought about the 24:1 mix as well b'c the 64' was the 1st year they changed to 50:1. I'll ask the mech. about it just in case !!
Thanks for your generous concern,
Sincerely ..................
 
Pappy said:
Yep, no mechanics around here............just check the profiles.
Click to expand...
I didn't mean to question you and meant no offense. I was glad someone (you) confirmed something I read about the oil mixture and felt more confidence in mentioning it to the guy I have restoring the motor b'c you confirmed what I was already questioning.
I joined this forum precisely b'c I humbly know very little about this hobby I'm pursuing. I use to know a bit about fishing for an 8-19 yr. old in the 70's but after a 33yr career traveling as a high-end finish mill works installer, I don't even know much about fishing anymore. I'm hoping there are many experts on this forum, including mechanics, fishermen, boat builders, marine painters, etc ... So far everyone has been supper nice and helpful and I appreciate all the input.
Sincerely ......................
God bless.
 
Point blank your engine still has 3-ring pistons that are not the later pressure back design. I would run a 24: 1 mixture for this reason alone. That engine is not bad on fuel and the extra oil protects against damage during an overheat much better than a leaner mixture will. Piston material is an older, softer compound as well vs. later pistons designed to stand up to lean oil mixes. Your spark is easily hot enough to eliminate plug fouling as long as you run a good lean idle mixture. Correct mixture will minimize smoke as well. Very often the marketing dept. was all too eager to introduce a change to the market whether or not the engineering dept. was ready to say....okay.
 

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