looking to buy used johnson...question value of compression test

[bluebrownie]

Is the compression reading a pretty sure fire way to determine if the cylinders are all ok...? for example ....i looked at a 70 hp johnson....compression was 120 in all cylinders.... does this give me a pretty solid way to determine if the head, cylinders etc. are all ok? thanks

 

[bluebrownie]

Re: looking to buy used johnson...question value of compression test

anyone

 

[bktheking]

Re: looking to buy used johnson...question value of compression test

120 across the board looks good.

 

[bluebrownie]

Re: looking to buy used johnson...question value of compression test

anyone else

 

[mikesea]

Re: looking to buy used johnson...question value of compression test

excellent compression,when was the impeller last changed,gear oil too every yr,have you run it,if not why,if motor laid up for a long time,carbs will likely need cleaning,give us the story of what you did as far as running etc,comp,is important,but how it runs and pums water important too,if it sat without running,u need a spark test too,at this point,dont worry about comp.its GREAT.hope u feel better,good luck and come on back,

 

[Boss Hawg]

Re: looking to buy used johnson...question value of compression test

excellent compression,when was the impeller last changed,gear oil too every yr,have you run it,if not why,if motor laid up for a long time,carbs will likely need cleaning,give us the story of what you did as far as running etc,comp,is important,but how it runs and pums water important too,if it sat without running,u need a spark test too,at this point,dont worry about comp.its GREAT.hope u feel better,good luck and come on back,

2nd that

 

[henrye718]

Re: looking to buy used johnson...question value of compression test

Test it in the water and run it at all RPM ranges for a good while that will tell you the overall condition of the engine. Shift it a lot, listen for odd sounds etc etc. Spin the prop by hand outside of the water look for bent shaft or wobbling prop.

 

[freddyray21]

Re: looking to buy used johnson...question value of compression test

good compression is a start. I think if a motor has good compression the rest of the problems are easy fixes.

 

[tashasdaddy]

Re: looking to buy used johnson...question value of compression test

compression is the hardest to fix, at 120 on all 3, you have a viable base to work with. carbs are extremely important on the 3 cylinders.

 

[kenmyfam]

Re: looking to buy used johnson...question value of compression test

Compression is a good starting point in determining a motors condition, however there are many other factors to consider.

 

[R.Johnson]

Re: looking to buy used johnson...question value of compression test

How old is this engine?