Good Compression?

[204Angler]

Did a compression check on my 1994 150 Blackmax the other day, getting ready to sell it. I got between 90-93 on all six cylinders. I know that the most important thing is that they be with in 10% of each other so I am good there. Was just thinking that last time I did one on another motor it was 103(ish) on all 6. Is 90ish good compression as long is it is even on all 6? It was rebuilt a while ago and it only has about 20-25 hours on the rebuild. Thanks

 

[lindy46]

Re: Good Compression?

Sounds a little low to me. How does it run?

 

[204Angler]

Re: Good Compression?

It runs very well. It pushes my 21' center console along at 38knots with full tank of gas (80 gallons), me and all required gear/fishing gear. It has excellent throttle response also.

 

[204Angler]

Re: Good Compression?

bump

 

[Barnacle_Bill]

Re: Good Compression?

The readings are even and that's what is important.

 

[204Angler]

Re: Good Compression?

That's what I thought! Good answer, thank you sir

 

[ezmobee]

Re: Good Compression?

You can, with good conscious, describe your motor as having "nice even compression"

 

[JB]

Re: Good Compression?

There is nothing in the engine that can cause all 6 cylinders to drop by the same amount at the same time. Nothing.

However, change the guage, battery, engine temperature, air temperature, residual oil in the cylinder walls, number of turns used to measure and the person doing the test and you are certain to get all 6 to measure differently.

 

[204Angler]

Re: Good Compression?

JB There is nothing in the engine that can cause all 6 cylinders to drop by the same amount at the same time. Nothing.

However, change the guage, battery, engine temperature, air temperature, residual oil in the cylinder walls, number of turns used to measure and the person doing the test and you are certain to get all 6 to measure differently.

Yeah, the only thing that I could think of that would make them all even but a little lower is the fact that it was not at op. temp. I had it idling for about 4-5 minutes but as cold natured as those engines are I should have ran it for another few minutes...got it good an warm. Also, a mechanic friend of mine said that perhaps carbon build up may be a cause. So I might run some seafoam carbon treatment through it. From what I've heard I am not too worried about it.
So yes, in good concious...I CAN say it is dead even on all cylinders