2 Mercruiser 5L EFI with all 16 Cylinders of 175 psi or more??

[mendonmountain]

Hello,
I had a pre-purchase inspection done on a couple Mercruiser 5L EFI engines (one circa 2014 and one from 2018). The cylinder compression readings were:

Port: 178,177,178,176,177,176,175,178
Stbd: 175, 177, 176,178,178,176,177,175

I was expecting readings in the 140-160 range..? Is this really good news or not so good news?

The engines are reported to have less than 200 hours on them.

Thank for any insight!

 

[Bondo]

Hello,
I had a pre-purchase inspection done on a couple Mercruiser 5L EFI engines (one circa 2014 and one from 2018). The cylinder compression readings were:

Port: 178,177,178,176,177,176,175,178
Stbd: 175, 177, 176,178,178,176,177,175

I was expecting readings in the 140-160 range..? Is this really good news or not so good news?

The engines are reported to have less than 200 hours on them.

Thank for any insight!

Ayuh,.... Welcome Aboard,...... I'd chalk it up to gauge variation,.....
Not all compression gauges read the same,.....
Nice even numbers are Great,.....

 

[flashback]

your gauge is a bit optimistic.

 

[mendonmountain]

I reached out to the guy who did the tests, and he said this:

"Initial readings were in the 150s, once I combined batteries they rose in the 170s"

"There are four batteries on the boat, I had to use the starter to turn the motor over to get compression"

"Don’t get too caught up in the overall number, the consistency is the best marker"

Considering the range for a Mercruiser 5L EFI is 140-160, does this make sense?

 

[alldodge]

Extra batteries only help to turn the motor over maybe a bit faster, but as Bondo said, it's just your gauge and not the amount of batteries.

You have even numbers across the board so your good

 

[Scott06]

X3 what AD and Bondo said these are great numbers but a bit inaccurate. All it shows is engines in great shape. What was one engine replaced? Or is this an older boat where repowers we’re done staggered ?
if in salt would be thinking water ingress due to exhaust manifold lack of maint .

 

[vroom ZOOM]

As long as they are consistent they are good. I once had a motor that would consistently kick out 210 psi on all 8 cylinders. I use my gauge a lot, and I know it shows the correct numbers, I even tried a fellow mechanic's snap on gauge, also showed the same. Never could figure out why the heck the compression was like that, although the motor ran just fine.

 

[Lou C]

the consistent readings are the main thing, and they are very consistent.
now it would be good if you also had an oil analysis