97 Johnson 115hp knocking sound

[spoony]

I have a 97 Johnson 115hp which I bought used 4 months ago. The engine has been running great except it was a little rough when idling. My last trip out a constant knocking sound started coming from the engine (sounded like it was coming from around the flywheel). The engine sounded find when I first cranked it but when I started it up after my 2nd or 3rd stop of the day I noticed the knocking sound, no warning lights came on. It knocks when idling and when running full throttle. I took the cover off and didn't notice anything out of the ordinary but then again I'm no mechanic. I have a seperate oil tank so I don't have to do the gas\oil mixture, I assume the ratio is good but is there a way for me to check it? I don't think this is the problem because neither of my oil warning lights came on. Is there anything I should be looking for that may be causing this. I was getting ready to take it in for service because of the rough idle and my rpm gauge not working then this problem showed up. Any suggestion as to what it might be so don't get burned at the repair shop? Any tests I can do prior to taking it in? I'm worried I might be getting ready to throw a rod or something.....Could this be a symptom of a rod getting ready to go? Thanks in advance.....

 

[Dhadley]

Re: 97 Johnson 115hp knocking sound

Post the model number so we know which 115 we are talking about.<br /><br />Good luck!

 

[spoony]

Re: 97 Johnson 115hp knocking sound

The model# is J115PLEEM.

 

[Dhadley]

Re: 97 Johnson 115hp knocking sound

Good. Its a 1999 115 60 degree looper.<br /><br />Hows the water pressure? What spark plugs?

 

[spoony]

Re: 97 Johnson 115hp knocking sound

It runs at 5 or 6 psi durning idle and about 16 or 17 psi at full throttle. I'm using QL78YC sparkplugs.

 

[Dhadley]

Re: 97 Johnson 115hp knocking sound

Good choice on plugs but the water pressure may be a bit low on top end. <br /><br />Heres what may have happened. Since the water pressur is down the water cooled reg/rec may be bad, that would explain the tach not working. If the "knocking" is more like a "ticking" it may be that the rings are starting to coke up and youre hearing piston slap. A de-carbon job should help that. <br /><br />Sometimes -- not always -- when those motors run warmer than they should (not hot enough to set off the alarm) the skirts of the piston can callopse somewhat resulting in a "ticking" sound. It doesnt seem to get worse and we havent really seen it hurt anything but its there. <br /><br />A "knocking" sound is different. That could be a wrist pin loose, a wrist pin bearing or a rod bearing. It could be a lower unit noise traveling up the driveshaft. <br /><br />While its in the shop I would suggest a pump kit and have them verify the warning horn and lights are working properly.<br /><br />Good luck!