motor running rough half rpms

I have a 1983 75 hp evinrude and it is taking a little while to plain out and the rpms are not as high as it should be. It almost seems as though it is not getting enough gas.

Re: motor running rough half rpms

You need to start with the basics. In a word - that means "tune-up". Troubleshooting requires that you isolate the problem to either fuel, spark, or compression. You do that by performing a spark check on all cylinders, fuel pump check, compression check, and a spark plug condition check, are just a few things to look at that don't cost anything. If the engine is not running on all cylinders it won't perform. If the carbs have never been cleaned that may be a cause. When the engine doesn't perform, squeeze the primer bulb. If it picks up, you have a fuel problem. You can do the same thing by simply hitting the choke (push in on the key momentarily). If the engine bogs down it's probably not a fuel problem.

Re: motor running rough half rpms

Ken....I have a 95 johnson 70.......it is doing the samething as yours is.......it's all but pulling my hair out....good luck

Re: motor running rough half rpms

Don't guess -- troubleshoot. If you have spark, compression, fuel, and timing is correct it will run if the engine is in good mechanical condition.

Re: motor running rough half rpms

Good advice given so far. Your motor is not running on all cylinders. The next task is to troubleshoot and find out why. Don't go tearing into something without first finding out where the problem lies. In no particular order:

A bad spark plug can cause it. Or no spark to the plug. A spark is defined as one that will jump a 7/16" gap in free air. Anything less is not a spark.

A crudded-up carburetor on the cylinder that is missing can do it.

Water getting into a cylinder can cause it.

Finally, a damaged cylinder can do it, which shoud be the first thing ruled out by doing a simple compression test.