PDA

View Full Version : Compression Test: 170, 170, 170, 170, 168, 165, 180, 170


ksdaoski
02-09-2012, 12:07 PM
Hey guys- Looking at an 07 boat with the 310 RTP

Compression came back as
Cyl 1 170
Cyl 2 170
Cyl 3 170
Cyl 4 170
Cyl 5 168
Cyl 6 165
Cyl 7 180
Cyl 8 170


Off hand, seems like good numbers to be. Any concern about the range between 7 and 8, 165-->180?

Thanks

jhall0711
02-09-2012, 12:13 PM
Those are great compression numbers. Some say within 10 % some 20%. At 10% of highest number you would have 18 PSI variance and you are well within that.




[QUOTE=ksdaoski;815428]Hey guys- Looking at an 07 boat with the 310 RTP

Compression came back as
Cyl 1 170
Cyl 2 170
Cyl 3 170
Cyl 4 170
Cyl 5 168
Cyl 6 165
Cyl 7 180
Cyl 8 170


Off hand, seems like good numbers to be. Any concern about the range between 7 and 8, 165-->180?

thatsmrmastercraft
02-09-2012, 12:26 PM
I would be comfortable with that. Had you run another compression test again, that reading of 180 would have likely come out closer to 170, in which case it would be virtually perfect.

Ole Miss Rebels
02-09-2012, 12:42 PM
i did a compression test on my 2005 mcx and if i remember correctly all of the numbers were between 205 and 210. does that sound right for an mcx? it had around 450 hours on it.

ksdaoski
02-09-2012, 12:44 PM
Perfect, Thanks for confirming-

skijwr
02-09-2012, 10:14 PM
I checked into this when I bought my boat.
MC owners manual shows:
2002 Predator TBI 5.7 --- compr 180 to 200 psi
2002 LTR 5.7 --- compr 180 to 220 psi

around 2005 and later, the MC owners manual shows:
all engines --- compr 100 psi minimum

a year ago I bought a 2002 MC with the predator 5.7 engine, the compression results for mine were all in the low 190s psi.

skijwr
02-09-2012, 10:22 PM
And I think I remember reading for various GM based 5.7 L V8 engines that anything from 150s to 190s psi was good, more importantly the variance from low to high numbers 10% maximum. I would say your numbers are fine.