1990 Johnson Lost Power

[trashfish]

First time poster......<br /><br />I have twin johnson 75s on my 22ft Mako. The starboard engine starts and idles fine. When both motors are shifted into gear, the starboard bogs down. This started out as a gradual problem. The engine would be running fine then suddenly loose power. After running for a while longer the power would regain, then drop off again. Now I get almost now power out of that engine. The RPM's drop when it is in gear only. When I fire the engine up in neutral, rpms good. I've changed the plugs, replaced the fuel lines and filters. Any other suggestions? With the mechanics in my area you have to tell them what the problem that needs to be fixed is, they are not good a troubleshooting. I'm an idiot when it comes to engine terms, so keep it basic. Thanks in advance for any help!!!

 

[Tracy Coleman]

Re: 1990 Johnson Lost Power

trashfish<br />Probably do not have spark to 1 or 2 sparkplugs. Start engine and warm up so it starts as well as it will, shut off a pull 1 plug wire off and restart engine- any difference? Put 1 on and pull #2 and restart- any difference? Same on #3. You have a sparkplug wrench? Pull them and see if they look the same, is one or two oily? Need to run a compression check, all about the same+-? <br />If you don't have tools, it's a problem. The first thing I would do is go to a dealer and get a service manual for your engine. This will walk you through what you need to know and let you understand what a mechanic tells you, or understand that the "mechanic" knows less than you and you need to go elsewhere.<br />Backfire

 

[Backlash]

Re: 1990 Johnson Lost Power

Hey trashfish,<br />Sounds like you're dropping a cylinder or two on that starboard engine. To check it out, start it up in the water & warm it up(don't start the port engine). Remove the cover and put it in gear (make sure the boat is securely tied up). Pull one plug wire at a time, listening for a miss. If that cylinder is making power, you'll hear the miss. If you pull a wire and there's no difference, you've found a bad cylinder. Once you've identified the bad cylinder(s) you can effectively troubleshoot the problem. Hope this makes sense. <br />Backlash

 

[Backlash]

Re: 1990 Johnson Lost Power

Hey Backfire,<br />Looks like we were typing almost at the same time. Sorry about that....... <br />Backlash

 

[trashfish]

Re: 1990 Johnson Lost Power

OK, I've followed the suggestions and I have found 1 bad cylinder (#2). Now what can I do. Or more appropriatly what can a mechanic do for me and what are ballpark costs? Thnks for the troubleshooting help!

 

[Backlash]

Re: 1990 Johnson Lost Power

Hey trashfish,<br />Glad you found the bad hole....now to determine what's causing it. Most likely spark related. Since you probably don't have access to test equipment, I'd suggest switching the coils between #1 & #2 to see if the bad cylinder moves to #1. If it does, that's a pretty good indicator that you've got a bad coil....easy fix....just replace the coil. If the miss remains at #2, you've got a more difficult problem to diagnose without test equipment. Best to take it in and have a mech take a look. Good luck.<br />Backlash