Compression for a 2000 Johnson 70 hp

[lillys]

I am looking at a 2000 70 hp Johnson to replace my old motor. The motor has been sitting for 1 1/2 years.The motor has 20 hours on it.I Hooked a battery to it
and checked compression.Top cylinder read 129psi, middle cylinder read 110psi,
bottom cylinder read 129psi . Is this good compression? What other things should I check before buying? Thanks

 

[HighTrim]

Re: Compression for a 2000 Johnson 70 hp

Compression is good, middle cylinder is a little low, but a decarb may even that out. Was smart of you to check the compression before buying. Read the FAQ "Awakening a sleeping outboard" before proceeding, it will cover things such as replacing the impellor etc...

 

[lillys]

Re: Compression for a 2000 Johnson 70 hp

Thanks for the reply high trim!! I have to make a decision on the motor or not today. The motor looks like a new one. Would the difference in compression be enough to scare you away from it?I can get the motor for a good buy.
Thanks

 

[HighTrim]

Re: Compression for a 2000 Johnson 70 hp

no, those numbers are good. A decarb could possibly even those out. If you can get it for a good price, those compression numbers alone seem good. Talking with the guy will give you a good impression of how well he maintains it. Ask him when the last time the lower unit oil was changed, water pump and impeller, plugs. If the motor is clean, seems well maintained, good compression and runs well, seems like a good buy. Have him idle it and make sure it idles well, check the temp gauge and see if it overheats at all.

 

[lillys]

Re: Compression for a 2000 Johnson 70 hp

Thanks again high trim! The boat owner is a widow and she said her husband only had the boat out for about 20 or so hours. When we checked the compression we noticed it still had black paint on original plugs.The cylinders and plugs looked dry as a bone with carbon build up on the plugs.We are going to crank it later today and let it run for a while then recheck compression, before I buy it . Thanks high trim, this is an awesome website!!!