I have an 84 boat with Johnson 140 hp. What should the compression be?

[Jeff2012]

Hello
I have an 84 boat with 84 Johnson 140. Had the compression checked and results were 131, 130, 126, 120.
Does anyone know what the compression should have been when this engine was new? Should I be concerned with the 120 cylinder?
Also what do you think these current compression numbers mean for preformance compared to when engine was new in 84? I was told from a guy who wants to buy my engine the new 140 in 84 was 150 lbs on all 4 cylinders and that now my engine is tired.
Thanks

 

[emdsapmgr]

Re: I have an 84 boat with Johnson 140 hp. What should the compression be?

I doubt any factory consumer V4 crossflow ever made 150 lbs compression. Normal cylinder compression should be within 10% of each other. The heads on that 140 were good heads-probably normal compression was in the 130+ range when new. You did not state which heads had what compression. It is normal for the compression on this engine to vary between heads-could be as much as 5 lbs. If one head is 130, 131, the other head is 126, 120 that is not out of the "normal" range. That engine was a sought-after model back in it's day. Don't be too quick to give it away.

 

[Jeff2012]

Re: I have an 84 boat with Johnson 140 hp. What should the compression be?

Just checked it again. When standing behind the motor, the upper top port cyl has 132, the bottom port has 130, the upper starboard has 127, the bottom starboard has 120.

 

[crb478]

Re: I have an 84 boat with Johnson 140 hp. What should the compression be?

I agree with emdsapmgr, your buyer is either unknowledgeable or blowing smoke. Your compression is good and that is/was a desirable motor

 

[emoney]

Re: I have an 84 boat with Johnson 140 hp. What should the compression be?

My '83 140hp had in the same range as yours and she's on her 4th owner and STILL tearing up the Gulf of Mexico. A decarb might help even out the #'s but I wouldn't worry about it. Sounds like somebody was just trying to get you to give your motor away. I always answer those folks with, "Well, I am SOOO glad we caught this. I couldn't have slept at night knowing I sold you a bad motor. Thanks and I hope you find a good one." They usually change their tone if they think you might know what's what.

 

[Bob_VT]

Re: I have an 84 boat with Johnson 140 hp. What should the compression be?

That is great compression....... Just FYI .....if the compression was 75 in all 4 cylinders it will still run fine. Being told 150 when new is a bit over the top.

My V-4 maintenance schedule I do ALL of this about every 3 years and some items more often

Decarb the motor just because it is good maintenance
Change the plugs
Rebuild the carbs
Change out the impeller, thermostats, water deflectors and head gaskets
Lower unit oil.....
Maybe flush the tilt trim oil
Make sure there is no fishing line wrapped up on the prop shaft...
Gently kiss the top of the engine cowling and have lots of fun with a great motor!!

 

[Jeff2012]

Re: I have an 84 boat with Johnson 140 hp. What should the compression be?

I see you are in LaGrange, I am in Chicago. Do you know a good Johnson/Evinrude Mechanic in the area?