compression test results - The Hull Truth

msc · 10-20-2003, 02:10 PM

Any theories on this would be appreciated.
Last year when my boat was winterized the compression results were as follows
port engine 2-100 1-105 starboard 2-105 1-100
4-105 3-100 4-110 3-105
6-105 5-100 6-105 5-100
This year the results were as follows
2-120 1-118 2-120 1-115
4-118 3-118 4-120 3-120
6-115 5-120 6-115 5-120
Same shop did the winterization. Engine hours at the end of season 2002 were 186...at the end of this season 300. Motors ran beautifully this year as well as last but seemed a little smoother whatever that means. The only difference was running this year with a maintainance dose of ring free all season.
It is my understanding from reading this forum that different techs get different results. But this seems like a significant increase to me. Thoughts?

Tsunami · 10-20-2003, 02:29 PM

Don't tell the non-belivers but it could be the ringfree, cleaner rings should translate into better or more compression. My only other thought is that last year the motormight not have been fully warmed up. Either way, those are good close numbers.

Kirk

www.geocities.com/reel_time_fishing_team/

gw204 · 10-20-2003, 02:33 PM

Could be different gauges, different mechanics, the ring free, different engine temps, etc.

The most important thing is that there is only a max of 5 psi difference between cylinders.

You're in good shape so don't worry. Run the test again next year and compare to these results.

Brian
1985 Grady White 204 Center Console
http://userpages.umbc.edu/~bmille4/sirreel/index.html

CB Haws · 10-20-2003, 02:39 PM

The other guys hit the nail on teh head. You just can not compair last year's results to this year's. Just too many variables. Just focus on the relationship of the readings to one another. Your numbers are almost to perfect.

RSB · 10-20-2003, 05:53 PM

Question on compression results. After the second tune up of my 2002 Yamaha F115, the compression results on one cylinder was about 20% lower then the other three cylinders. Performance is off a little . Dealer felt probably lifter issue ($500 repair) and not covered by warranty. Also thought compression might increase with warm engine. Suggestions.

auguste · 10-20-2003, 07:28 PM

Two excellent points were made

Compression ratios are close to each other and that is good

Leak test will determine how long pressure is maintained . . . good test on wear

My mech used to do both tests on my mercruisers each year and he recorded the results in my log

Miss-Be-Haven

"49.6 mph on a beautiful calm day . . . fully loaded"

" The only boat without a ding or four, is the one that never gets used!!! "

KevinM · 10-21-2003, 07:32 AM

RSB - The Yamaha F115 is overhead cam, what lifter issue? OHC engines don't have lifters. It may have hydraulic lash adjusters! Even so, why would this not be part of the full 3 year warranty. Something doesn't sound right!

RSB · 10-21-2003, 08:05 AM

Thanks for the input. Should I contact Yamaha directly (who?).

KevinM · 10-21-2003, 09:37 AM

Don't know if this number is still valid 1-800-962-7926 Yamaha tech support.