Leakdown test on merc

**KIRCHNER** · 09-27-2018, 06:48 PM

Originally Posted by Merclover

Believe need test with 100psi

read too much will blow oil away where it normally be? im gonna try both low and high tests and compare....

**eli** · 09-27-2018, 07:01 PM

50 psi air x 2 on reading dont use a ratchet .

**Merc 2.5** · 09-27-2018, 07:02 PM

Never heard of that? But there's alot I'm still learning also, That's just my info but it also come from some very well known builders , if piston and rings can hold 150psi compression, should b able hold back 100psi. Blow oil away? Leakdown doesn't crank over so really shouldn't matter , just trying see a % of air leak past rings?? Maybe I just didnt understand the? Fully?

**Merc 2.5** · 09-27-2018, 07:03 PM

Ok so maybe its 50psi or 100.i guess. Just guess people ha e diff techniques

**KIRCHNER** · 09-27-2018, 07:16 PM

ive got 2 pair visegrips. should i put on my helmet? LOL 50 PSI it is.

**eli** · 09-27-2018, 07:42 PM

At 50 you can use breaker bar and rotate assembly up to tdc

**KIRCHNER** · 09-28-2018, 05:31 PM

I not sure about x 2 on reading ? i dont think my gauge is baseing % at 100 psi input. it says 4 oclock position on right gauge is 0 leakage., when left gauge is at 25 psi. doing it tomorrow rain or shine. let u know what i come up with. i would think 100psi would leak 2x 50 psi???? not sure about that!

**Merc 2.5** · 09-28-2018, 06:11 PM

Maybe few will chime in on this?

**superboattwin250** · 09-28-2018, 07:12 PM

I do all mine at 100psi. Always have.

**89Talon18** · 09-28-2018, 07:35 PM

Post a pic of the gauge so we can see what your working with. At 100 psi its easier to figure your leakdown percentage on the fly, for example if one gauge says 100psi and the other says 95 psi then you have 5% leakdown, i would recommend you NOT to use a breaker bar or a ratchet @ 100 psi to hold the flywheel at TDC your safer to use a piston stop or what i like to use is a dial indicator to find absolute TDC and then charge the cylinder and get your readings.

**Merc 2.5** · 09-28-2018, 07:49 PM

Ok now we r getting sumwere. I dont have enough experience with it to explain things. Also at 50psi can show less leakage?

**eli** · 09-28-2018, 08:19 PM

i use 100 tried 50 it worked ok say 50 psi going in 48 out then its 4 %

**89Talon18** · 09-28-2018, 08:27 PM

Im not sure if it will leak more at a higher psi that it would be at a lesser psi but what i think eli was saying if you use 50 psi and you have for example 47 psi on the other gauge is to double both numbers to find your percentage quciker that breaking out the calculator

**89Talon18** · 09-28-2018, 08:38 PM

Eli you beat me to it

**KIRCHNER** · 10-02-2018, 02:40 PM

I TRASHED the right side gauge and bought a 100 psi coupled it all together. i like the idea of compairing the two gauges, i can crank in 100 with reg a read the right side and a little math., should be accurate. guy o utube made a nice one for 20 bucks, used 2 100psi gauges. il have some # tomorrow. thanks guys....MY reinvented gauge was a flop tested both independently 1 reads 100 other 80. i cant win. gonna use the CCMS method, makes more sense the TDC test.