compression check should be around?

[joe_dirt]

i have a 1977 35hp rude and like to know whats a good reading for a engine this old and how long should i crank it for to get a reading

 

[WillyBWright]

Re: compression check should be around?

I let it crank 7 to 9 times. On my gauge I'd want to see more than 100 psi. You don't need to open the throttle like you would on a 4-stroke.

 

[OBJ]

Re: compression check should be around?

Anything above 90psi is considered good Joe. More important is how the compression readings compare to each other. Generally ya' want the cylinders within 10 to 15% of each other. So you could have, for example, 85 and 90 psi but they are well with in specs.<br /><br />If the compression seems a little low, do a decarb and retest.<br /><br />Let us know what ya' find.

 

[joe_dirt]

Re: compression check should be around?

thanks guys i,ll start testing it tomorrow