71 johnson outboard compression

[sean123]

hi all i just got a arrowglass with a 71 johnson 125 on it anyone know the compression # on it the 1st cyl seems low.

#1cyl 115 <top>
#3cyl 155 <bott>
#2cyl 150 <top>
#4cyl 150 <bott>

anyone got a clue let me know the motor hase been sitting 2yrs the guy i got it from says he rebuilt the topend 2yrs ago??

 

[jtexas]

Re: 71 johnson outboard compression

Difference between cylinders is more important than the actual numbers - you want the lowest to be within 5% - 10% of the highest. All four at 115 would be good but the numbers you report are problematic. I guess you tested more than once, just to be sure?

It hasn't been run since it was overhauled?

 

[DJ]

Re: 71 johnson outboard compression

sean,

You have a problem. All the numbers look great except the #1. Re-ckeck it.

The real point is to have all four as close to each other-as possible.

Do a "decarb" (see above "frequently asked") for details.

#1 might come back. Chances are better than you think.

 

[sean123]

Re: 71 johnson outboard compression

the guy said he ran it for 2 hrs after the overhaul. i will try to de-carb and see what happens. thanks 4 the help


btw: i got it to run in the lake with spraying gas in the carb, but when i give it trottle it boggs and dies??? the guy i got it from said it overheated thats y he rebuilt it.

 

[sean123]

Re: 71 johnson outboard compression

i tryed all cyl. 6 times each thay came out the same

 

[RobSS]

Re: 71 johnson outboard compression

I am having a similar problem with mine dying when i give it throttle. I took it out on the river and it ran like a raped ape slowed down for a no wake zone and it died. When i tried starting it up it would idle but when i gave it gas it would sputter and cut out. i took it home checked the compression on all the cylinders. all were at 95 psi although this is low they were all the same. I thinking maybe i am having a synchronization issue. Did you try putting a table spoon of oil in your cylinder and checking the compression again? this will temporarily seal it and let you know for sure if its your rings or if you have another issue.

 

[bktheking]

Re: 71 johnson outboard compression

Start a new thread please, you attached to a thread from 06.