I own a 1994 Evinrude 150 hp that starts and runs great. What kind of compression numbers should I expect to see on this engine? When should I get concerned? How do I know if I need to decarb the engine? Thanks in advance!
I own a 1994 Evinrude 150 hp that starts and runs great. What kind of compression numbers should I expect to see on this engine? When should I get concerned? How do I know if I need to decarb the engine? Thanks in advance!
All compression testers vary in their readings, but about 95 PSI and above is fine. As long as they are within 15% of each other you are OK. Best practice is to decarb every 100 hours. Hope this helps.
Hey championman, I was always told compression should be within 10% of each other, your thoughts please.
<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by 28 chopper »</td></tr><tr><td class="quote">Hey championman, I was always told compression should be within 10% of each other, your thoughts please. </td></tr></table>
Tech schools and manuals say you are OK at 15 % the confusion comes in at the pressure readings. Bottom 2 cyls always read less due to carbon build up, as they are at the exhaust pipe.If the uppers are out of whack then you have an issue.
Thank you,
Retired E-8 3rd Bn 5th SF group, Ft Campbell, Ky.
I checked my compression yesterday and all 6 cylinders read 80-85 psi. This seems low to me for a 150 hp Evinrude, but it cranks and runs great. I even questioned my gauge accuracy and bought a new compression gauge. The results were the same. Should I just try a decarb and keep running it without any worries?
Decarb her, she may have some stuck rings....
OK, I'll do a decarb and see if that helps! Is Seafoam spray in the carbs the best to decarb with or is there a better product? Thanks, Mike.
Nosir... I'm a FIRM beliver in Engine Tune from OMC/BRP. Buy a can from your dealer and read the instructions on the can. What's not on the can is DON'T do this on mama's drive way or with the rear of the engine facing the house. After doing the decarb, preferably afternoon, let her sit over night, and take her to the lake the next am....after a good warm up, let her EAT!!!!! for a good 15 minutes or so....Bring her home and change the plugs, and check comp at that time.....Almost garuntee the numbers will come up some, if it hasn't been done for a while. Then do it once a season or 100 hours whichever comes first.....She'll love ya for it.
Thanks for the help, I'll do the decarb as you suggested as soon as I can, weather permitting. I'll report back with the results when done.
OK, today I bought some OMC Engine Tune and sprayed in the carbs of my 94' Evinrude 150 per instructions. Tomorrow I plan to take it on the river and run it. Then when I get home, I will check compression and change the plugs.
Don't let is sit more than 16 hours or you could have metal migration.
After spraying a can of OMC Engine Tune in my carbs yesterday afternoon, I took the boat on the local river this morning and ran it 15-20 mins pretty hard. I fished for awhile and ran it some more. Fished for a while longer and made a long ride to the ramp and headed home. At the house I checked compression again and the numbers were unchanged. I didn't get much stuff out the exhaust yesterday like I thought I might. Maybe there wasn't much carbon buildup. Anyway, I can't complain about the way the engine performs. It cranks after warmup first turn of key all day and runs great on top end. I was just trying to do preventive maintenace. Maybe I need to do another decarb. A second time might break some stuff loose? Not sure I'm going to worry about it anymore. Thanks, Mike.
<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by Boat4Life »</td></tr><tr><td class="quote">After spraying a can of OMC Engine Tune in my carbs yesterday afternoon, I took the boat on the local river this morning and ran it 15-20 mins pretty hard. I fished for awhile and ran it some more. Fished for a while longer and made a long ride to the ramp and headed home. At the house I checked compression again and the numbers were unchanged. I didn't get much stuff out the exhaust yesterday like I thought I might. Maybe there wasn't much carbon buildup. Anyway, I can't complain about the way the engine performs. It cranks after warmup first turn of key all day and runs great on top end. I was just trying to do preventive maintenace. Maybe I need to do another decarb. A second time might break some stuff loose? Not sure I'm going to worry about it anymore. Thanks, Mike.</td></tr></table>
Thank you for the update, usually if a decarb hasn't been done in a while, the decarb will free up some rings sticking and up the compression a little. It will definately help keep your engine in good shape. Unless Fred or Jughead, or Seahorse say different, I'd not worry about it and enjoy the rig.
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