1985 evinrude 4 hp

Hello everyone!<br /><br />I was hoping someone could help me. I have a 1985 evinrude 4 hp motor. I can only get it to start with the throttle 3/4 full. It will then idle when you move the throttle lever close to idle but eventually stop. When in neutral I can rev the motor to high rpm. when I put it in gear it bogs down. You can give it full power and it goes 1/4 speed. If you pull the lower end out of the water it seems to rev up to full power but put it back in the water it slows down. I just put new spark plugs in. The primer bulb stays pumped. The engine dies immediately when fully choked and will not start choked. I pulled the bottom spark plug wire off while the engine was running and it continues to run, put it back on and pull the top off it dies. I don't know enough to diagnose much further. Hoping someone with more insight could help.<br /><br />Thanks<br />Ashton

Re: 1985 evinrude 4 hp

Ashton,<br />Welcome to the iboats forum. You said that pulling the bottom plug wire makes little or no difference in the running of the motor. That cylinder is dead. Pull the plugs and do a compression test on both cylinders. Do a spark test by putting the spark plugs back into their boots and hold the spark plug body against the engine block (one at a time) and pull the rope start and look for spark to jump the plug gap.<br /><br />Report back after you have this information. Depending on your results, we can go from there.

Re: 1985 evinrude 4 hp

Pulled the plug on the bottom. The motor runs just fine on the top plug so I would assume the top plug is fine. I put the bottom plug in the boot and it fires when held the the casing. You said to check the compression. I was wondering how I do that. Thanks for your response. I appreciate your time.

Re: 1985 evinrude 4 hp

I also put the bottom plug cap on the top plug and it will no run. It only runs top plug cap to top plug.

Re: 1985 evinrude 4 hp

A screw-in type compression tester (same threads as a spark plug) are the easiest to use. Do the compression test on both cylinders. Both readings should be within 10%, or so, of each other.<br /><br />You can swap coils and see if the problem moves to the top cylinder. This would point to a bad coil. If the problem persists after a coil swap, then the CD ignition module is suspect.