low compression????

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dhonda

Seaman Apprentice
Joined
Aug 1, 2010
Messages
43
hey, i have a 1960 gale 40hp that i took out the other day and when i did so i noticed that after driving it for 10-15 mins at a crusing speed the motor starts surging so when i took the motor home i bought some new fuel lines and cleaned the fuel pump filter. I also checked the compression and noticed that the top cylinder has 80psi and the bottom has 70psi, keep in mind that i used a cheap harborfreight compression checker. My question is how low does the compression have to be to effect the performance of the engine?

Thanks, Derek
 
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dirtdog38

Seaman
Joined
Jun 29, 2011
Messages
53
Re: low compression????

i like to see over 100. but they will run with less than u have. the suge id say is a diffrent thing going on bad gas or points , carb look ther run a little more oil in the gas on that old motor they like it. as long as you dont foul plugs is the main thing ther
 
watergecko

watergecko

Petty Officer 2nd Class
Joined
Dec 1, 2010
Messages
111
Re: low compression????

80/70 is ok, what ur looking for is within 10% on the cylinders, ur at 12.5% but i think u might b able to improve those numbers by doing a decarb. Check out the top secret file at top of thread for how to. Do a decarb, and redo the comp test, u may just have a sticky ring.
 
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