Reply To: 1983 70 HP Johnson poor running

[Don]

johnrude wrote:

Fleetwin,
I put a rebuild kit into the fuel pump and will replace all of the rubber fuel line pieces. I’m waiting on a replacement high speed jet before it all goes back together again. I will rig up something to test the individual cylinders response to the selinoid choke injection as you suggested. Your appraisal of a fuel issue feels correct. It starts, runs and idles as it always had. I will try the spare fuel tank and if there is a reocurance, try the hose bulb primer. I hope it’s got nothing to do with the reed valves as they don’t seem to be available anymore.

We are not trying to scare you when we mention the water intrusion possibility. Unfortunately, this engine series is more prone to water intrusion due to its complex exhaust manifold. I always recommend retorquing all those manifold bolts frequently to avoid this situation.
I am pretty confident that your situation is a result of a fuel restriction somewhere, especially when you mention the little black flakes in the carb bowls. Perhaps your boat’s fuel system is messed up creating a fuel restriction/air leak also, which is why I recommended trying a different tank/hose.
Not to worry about the reeds being messed up, that would be my last “guess”. Messed up reeds are more likely to be noticed at idle. But, as always, anything IS possible.

You could also try the “oil can method” if results from the primer test are inconclusive. In other words, fill a little oil squirt can with 50:1 mix, and remove the air box cover. Have an assistant drive the boat and get it to misbehave. Give each carb throat a little squirt, one at a time, to see how they respond.
RPM should drop on a good cylinder
RPM will pick up briefly on a cylinder starving for fuel
No response either way usually means that cylinder is not firing at all for some reason. I wouldn’t expect this result in your situation