New to me 8 hp Evinrude. Revival questions

[ShoestringMariner]

I just picked up an 8 hp Evinrude. I followed a lot of the procedures in the secret files. I’m not doing it exactly as written because I want to know if it’s a keeper first. Of the first things I checked was the lower unit oil, spark and compression.

this model looks quite clean but has reportedly sat for quite a while. the compression is lower than I like to see. Both cylinders come in at about 100 psi. This motor was pretty wet. Looks like it was fogged pretty heavily. So the compression numbers concern me.

I can get the motor to fire on squirt but not through the carb. My assumption is that it needs a full carburetter rebuild/cleaning. But before I get too deep into this thing, is this compression normal for these motors. I seem to remember something about Evinrude Johnson being lower compression Motors but that may have been 50s and 60s Motors. This one’s a 93.

Any thoughts?

 

[jimmbo]

https://forums.iboats.com/forum/eng...231-awakening-a-sleeping-outboard-by-boatbuoy

 

[ShoestringMariner]

Thank you, yes I have been through that thread. And a lot of it my usual go to. My question was poorly asked. I should’ve just asked; what is the factory compression rating was on these motors to begin with?

100 psi seems only fair in my books compared to the 130 psi my 650 merc has

 

[racerone]

Many arguments / comments about compression values.----100 PSI is not bad.-------Do not compare a 650 Merc with a wee 8 HP Evinrude.

 

[Crosbyman]

none of my oldies from the 50s..70s (mostly 3-15 hp) have ever reached the 100s psi…and they all run ok

I would just clean it up and run it for now ….and who knows compression may even rise after a few good runs to wake it up

 

[racerone]

I have 2 of these 8 HP models on hand now-----Would you like me to post the numbers on them ???

 

[ShoestringMariner]

Many arguments / comments about compression values.----100 PSI is not bad.-------Do not compare a 650 Merc with a wee 8 HP Evinrude.

Thanks, I wondered if smaller motors were typically lower compression to aid in hand starting.

 

[ShoestringMariner]

none of my oldies from the 50s..70s (mostly 3-15 hp) have ever reached the 100s psi…and they all run ok

I would just clean it up and run it for now ….and who knows compression may even rise after a few good runs to wake it up

Same with my oldies. I have a good running 58 QD that is maybe 85 psi, but I also have a 57 FD11 that is really tight and runs GREAT. One of these days I’ll check it’s numbers.

 

[ShoestringMariner]

I have 2 of these 8 HP models on hand now-----Would you like me to post the numbers on them ???

Wow, if you don’t mind, I’d really like to know!

 

[racerone]

Tested one of the motors just now.--------120 top and 115 bottom.--------And I know my gauge is accurate.-----And compression numbers have nothing to do with " hand starting " in my opinion.

 

[ShoestringMariner]

Tested one of the motors just now.--------120 top and 115 bottom.--------And I know my gauge is accurate.-----And compression numbers have nothing to do with " hand starting " in my opinion.

Excellent, thanks for doing that for me and others who are interested

 

[jimmbo]

Thanks, I wondered if smaller motors were typically lower compression to aid in hand starting.

A lot of OMCs V4s only had 5:1 or 5.5:1 compression in the 60s. The biggest twins OMC made inthe 50s and very early 60s had a compression relief system to aid in starting, other engine used an elliptical winding of the starter rope on the recoil to increase leverage during the compression part of the pull

 

[ShoestringMariner]

Well fellas, it turns out the only thing I had to do was fix the air leak in my fuel tank connection. Fuel pump is clean. I didn’t bother pulling the carb.

Purrs quietly. Smooth. One pull start when warm. I still have to check it stone cold now that it has had fresh fuel in it.

I’ll change the gear oil and run it as is with seafoam in it and see how it goes as a kicker. At this point, 100psi compression doesn’t bother me in the least

thanks for your help

 

[racerone]

Install a new impeller now.

 

[ShoestringMariner]

Yes, I forgot to mention that. it will be part of the lower end service

 

[raczekp1]

if its model with rope starter on te top of flywheel , so this motors has cylinders bored with pin hole in exhoust side to lower compresion i think

 

[ShoestringMariner]

if its model with rope starter on te top of flywheel , so this motors has cylinders bored with pin hole in exhoust side to lower compresion i think

Thanks. The rope starter is in a vertical recoil next to the carb, not on top over the flywheel

 

[racerone]

So then this motor is not a 1993 model.------You should always post the model # or some pictures.

 

[ShoestringMariner]

So then this motor is not a 1993 model.------You should always post the model # or some pictures.

Correct, it is s 90. I made an error in my original post.