is this good compression readings?

[gopedgsr40kid221]

I have a 45hp Honda and ran a compression check. Top cylinder 135psi middle 140psi bottom 150psi Is this good compression?

 

[Barnacle_Bill]

Re: is this good compression readings?

Keep an eye on that top cylinder.

 

[TOHATSU GURU]

Re: is this good compression readings?

No, it's not a good set of readings. It indicates excessive wear, stuck ring, scored block, etc. However, its not so bad that you couldn't get away with using it...It's just that you no longer have a margin to get worse and still run.

 

[mercfixer]

Re: is this good compression readings?

In my humble opinion, i would give er a green light !!!!
How dependable is your gauge, do you have the throttle wide open, is the motor warm or cold,,,,
these are all factors to be considered, in thirty five years of repairing marine engines, it is a rare event that a motor, particularly an outboard motor, will have a compression reading exactly the same as as the other cylinders.
Oh yes.....some would argue until blue in the face that the cylinders should be exactly the same.....manufacturers manuals will ALWAYS give a "plus or minus" factor in the form of a percentage, or in p.s.i. You could check the valves by having a compression leakdown test done. I have purchased more than one motor with variations in compression readings of over 10 % variation and found them to change due to other conditions such as a higher reading on a cylinder due to excessive fuel in the cylinder due to a stuck carb float and fuel trickling into the cylinder, broken or cracked reed plates on two strokes will lower the readings at times. After a warmup the readings can change
Hope this helps......

 

[hondon]

Re: is this good compression readings?

If you are nervous about those numbers ,the next step is a leakdown test.What is the problem you are trying to solve,and why do you believe it is compression related?

 

[JB]

Re: is this good compression readings?

Well, I rarely disagree with TG, but here I do.

Looks like a case of psi paranoia to me.

The span is 15psi, right about 10%.

No bad cylinder is going to read 135psi, even in a 4 stroke.

Quit frretting and go fishing.

 

[TOHATSU GURU]

Re: is this good compression readings?

Well, I rarely disagree with TG, but here I do.

Looks like a case of psi paranoia to me.

The span is 15psi, right about 10%.

No bad cylinder is going to read 135psi, even in a 4 stroke.

Quit frretting and go fishing.

PSI paranoia Probably true. I was thinking more in terms of gopedgsr40kid221's question of "is this good compression?" It's acceptable compression, but its not good compression. Good to me and I admit I am paranoid, is 5 psi or less difference between cylinders. Wear should be even between cylinders with normal use. When it's not its an indication that something was or is not right. So, do I think that he should not worry about it and go fishing?...Yes, sort of. On an otherwise healthy engine I wouldn't tell him he needs to tear it down today. But, I do think that he needs to keep an I eye on it in case the gap widens between cylinders. So says my paranoia anyway