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Author Topic:   Motor woes
rsgwynn1 posted 06-22-2002 09:41 PM ET (US)   Profile for rsgwynn1   Send Email to rsgwynn1  
My 1989 225 Evinrude started missing badly at high rpms today. I had to come back ten miles at 2500 rpms (10 knots). Anything higher and it would start missing and backfiring badly. When I got it home I ran a compression check, which seemed ok, and I cleaned the plugs and fired it up in my flush tank to run the salt water out. Very smooth at low rpms but rough when higher. Any ideas? Only thing new is that I added some Techron carbon guard to the last fill up with gas.
Peter posted 06-22-2002 10:34 PM ET (US)     Profile for Peter  Send Email to Peter     
Speed Limiting Overheat Warning (aka SLOW) kicking in? Friend of mine had the same engine do the same thing and it was an obstructed cooling passage causing one of the cylinder banks to run hot and the SLOW to kick in.
rsgwynn1 posted 06-23-2002 11:38 AM ET (US)     Profile for rsgwynn1  Send Email to rsgwynn1     
What do you recommend? Pulling the heads and looking for a blockage?
David Ratusnik posted 06-23-2002 08:24 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
Coils x 2. My usual answer. .03 David
Peter posted 06-24-2002 07:41 AM ET (US)     Profile for Peter  Send Email to Peter     
If there is an obstruction, you may have to pull the heads to clear it. However, I think you have to diagnose that it is the SLOW circuit that is kicking in before you consider pulling the heads.

If you are getting well above 2500 rpm but the engine is misfiring, then it may coils, as David suggests, or something else.

From what I've seen, if the SLOW circuit is kicking in, the motor will seem fine below about 2000 rpm and above that will buck and carry on like its being stung by a swarm of bees.

rsgwynn1 posted 06-24-2002 11:55 AM ET (US)     Profile for rsgwynn1  Send Email to rsgwynn1     
I pulled the heads. Lots of carbon on the pistons after about 15 hrs. of running since I cleaned them off. I also note the absence of any water passage diverters in the block. My V-4 OMC motors had them. Does this one?
rsgwynn1 posted 06-24-2002 11:56 AM ET (US)     Profile for rsgwynn1  Send Email to rsgwynn1     
2000 rpms may be right since my tachometer seems to run fast.

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