Reply To: compression loss due to hose on gauge

[The red boat]

my gauge works just fine for 99% of my applications.
that wasn’t the problem.
I’m not experiencing unusual or low compression either.
both cylinders are showing almost identical compression at close to 100 psi.

I was just curious about the air in the hose and how much of an effect it would have when measuring compression on a small outboard.
this was based on many, many other posts on AOMCI discussing the very same thing.
I wondered if there was a factor or rule-of-thumb that would apply to a gauge that had the valve next to the gauge vs. one that had the valve at the other end of the hose.

doesn’t sound like there is or would be a consensus on such a factor.
the only way to get such a number would be to buy the type of gauge that screws directly into the block and compare the numbers with the other gauge.
i was trying to avoid buying another gauge if someone had a ballpark number that i could apply to my original readings.

seems that answer is nope.

thanks for all the replies.