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Old Johnson V4 75HP Compression

B

bobby

Member
" I have heard many stories on

" I have heard many stories on what the Compression should read on this old 1963 Johnson SS V4 75hp

What should it be Before it needs a rebulid?

Last summer I was working on it and the comp reads
78 on 3 cylders and 82 on 1.

I was told buy an old boat repair shop this is good for the year and motor.. Is this true,,

Others tell me it should be at 110-115 psi On all.

I told the lady at the boat shop this and she said NO.. That is for the newer motors.. These older ones dont have that high of Compression,

O What is Right.. as my head spins..

Thanks 4 your help and time.
Bobby "
 
" Hey Bobby.... Run the engine

" Hey Bobby.... Run the engine until it warms up good...Then remove 3 of the plug wires and try to start it again...should give a good hit on that cylinder...do the next 3 the same way...If all hit strong, then the motor has enough compression to run well,and thats what you'r after...OMC stoped years ago putting compression stats in their service manuals.... "
 
" Thanks I will do this,, It S

" Thanks I will do this,, It Starts fast. idles fine.. Just wont go when it is in the water..
Thanks again,
Bobby "
 
Hey Bobby...
Sounds like you

Hey Bobby...
Sounds like you need to take the carbs off and clean them...The high-speed jets are clogged up and cant supply enough fuel to give the engine power enough to run much above a fast idle....Tom
 
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