1988 Evinrude 4hp

[TexasJackofAllTrades]

Was in my friends garage for many years and after a flood was partially underwater for a bit. I have been able to get it to spin and can freely use a drill to spin it over, cleaned the carb, cleaned the ignition system, woodriff key is in position... have a nice spark!..... the compression is 25. It won't start and acts as if there is no spark or no fuel.... but it has both! even with squirting start fluid directly into the plug holes it acts as if there is no spark (just a little at first then graduating to quite a bit).... cannot even get it to pop once. Very occasionally It does seem to have a tiny back fire. Is the compression so low that it has no chance? I'm hoping the rings just need to get freed up a bit... what do you think about pulling the motor and just soaking the hole thing in a bucket of cleaner?? Is it worth rebuilding... thinking about just retrofit a Briggs. I did remove the head and inspected... looks fine. reinstalled and torqued no leak there..

 

[backwater52]

25 lbs is dismal, new head gasket?

 

[matt167]

It's not going to run with 25 PSI. That twin engine runs smooth when it's right. It was built for 20 years pretty much exactly the same with some ignition differences through the years. Parts are cheap and plentiful.
I have a 1997 that was lightly locked up when I bought it ( now runs mint ), but it still blows over 100 PSI on both cylinders.

Put some oil in the cylinders and see if the compression comes up. If both cylinders blow 25 PSI, than you have a compression leak between cylinders

 

[oldboat1]

could be your compression tester or technique. Borrow another tester (screw in style with a pressure relief button). Make sure you screw it in enough to compress the O-ring. Try with both plugs removed, and crank until the needle stops moving, then note reading.