I have a 1989 88 hp Evinrude, Model E88MSLCE Serial R8208688, with 80 compression on all cylinders. How can I find out if it has low compression heads?
And when you took the readings - which are all close - how did you do it? That makes a big difference - as does the compression tester (they vary).<br /><br />The right technique can give a different reading.
OMC never published a given number, just a variance. The variance should not be more than 15 lbs from high to low according to the OE service manual. <br /><br />If all were exactly 80 I'd try another gauge. They wont be exactly the same. They'll vary slightly -- thats normal.
Motor should be warm, all spark plugs should be removed, plug wires grounded, throttle should be fully advanced (wide open throttle plates), with a fully charged battery.<br /><br />If any of these are off you will have a low reading...<br /><br />Did I miss anything experts??????
Dhadley: Got a compression tester and tested the compression myself. My engine will not turn over with the throttle wide open, so I checked it in the neutral position. It checked 113, 110,112,110 respectively. This was with the engine warm.
Good numbers. If you havent done a decarb in a while it might be a good time to do so now that you have a baseline. Good info to keep around.<br /><br />It'd be interesting to see what the mechanic says now who said the compression was 80. Probably not worth the time though.
Just a thought for future refrence. <br /><br />If you disconect the throttle cable at engine and leave throttle control lever in neutral.<br /><br />Turn carbs. to full throttle and block open. The resaon they need to be wide open is because the more air you can get into cylinder the higher your compression numbers.<br /><br />It wont go up by much, but uh little...welt usualy anyways.<br /><br />Luck to ya!
dHadley: Installed an SE Sport Hydrofoil. Planes beautifully with the Raker 13.5 x 18. WOT still low at 4900 RPMs, 39 gps. Changed to a 13.5 x 17 aluminum prop and could not tell much difference in plane time and picked up approximately 100 RPMs, 40 gps. Did a decarb while fishing. What is my next step to increasing RPMs to 5500 and maintaining speed?
Well, somethings not right. 5000 rpm with a 17" prop with that V4 has a theoritical speed of about 40.5 mph with 0% slip. So, if youre doing 50 (GPS) thats really good. Too good to be true.<br /><br />To go 50 with 10% slip with a 17 we'd have to be turning the motor about 6800 rpm. With 5% slip youd still have to be turning it about 6500.
You might check motor virticle height.If there is room you could pick up about 3 mph if you can raise the motor one inch.Quite a jump for no money invested.Depending on where the anti vent plate is raise it a little at a time until just before ventilation becomes a problem.Be sure she stays cooled.
