Johnson 2003 150hp compression

[hcarney]

what should the compression be on a 2003 johnson 150hp i'm getting a reading fo 60 on all 6 cylinders

 

[Barnacle_Bill]

Re: Johnson 2003 150hp compression

Since all cylinders are reading 60 I would say either you have a defective gauge or you are not doing the test properly. Are you turning the motor over until the needle stops rising?

 

[boobie]

Re: Johnson 2003 150hp compression

Do you have all the plugs out when checking ? Also agree with a bad gauge. And last, does the mtr run??

 

[hcarney]

Re: Johnson 2003 150hp compression

Do you have all the plugs out when checking ? Also agree with a bad gauge. And last, does the mtr run??

All plugs out throttle full open cranking until needle stops rising. I also thought it was bad gauge so i purchased a new one same reading.Engine starts fine runs great but i lost about 250 rpm full throttle is 5150 was 5400 before.

 

[boobie]

Re: Johnson 2003 150hp compression

You should do a good decarb on it and see if the compression improves.

 

[JB]

Re: Johnson 2003 150hp compression

Those big V6s were low compression engines. I would expect readings of 70 to 90psi, but I think you have a healthy engine and did something imperfect in testing. Throttle position is irrelevant, but engine temp is important. Look in the Top Secret File for a reliable compression testing procedure.

As boobie suggests, a decarb might make a difference.

 

[SparkieBoat]

Re: Johnson 2003 150hp compression

unless that motor had a lot of hours on it, it would be unusual for all cylinders to lose exactly the same amount of compression. if it is cold where you are that can effect it that way. I had an engine that had 95 on all cylinders during the summer and this winter went to sell it and could not get compression over 75..it was really odd, even after I let it run for 10 mins. it ran so good the guy bought the motor anyway. it was an 1989 200 johnson..now I regret selling it. man that was a dependable good motor.