70 HP Johnson running rough

[stelladallas]

Was on the lake today and our 70hp Johnson was running fine when all of a sudden it started missing very badly. Started smoking also and an alarm started sounding. Pulled over to a pier and cleaned prop of milfoil. Started the motor back up and it would run pretty good at a slow speed, but when throttle was applied, it would start missing again. It didn't seem to be running hot and the water pump was still pumping. Help please! Checked all 3 spark plugs and all 3 looked fine.

 

[David Greer]

Re: 70 HP Johnson running rough

I'd be concerned about your oil pump.

 

[stelladallas]

Re: 70 HP Johnson running rough

Thanks David, but we mix our oil with our gas and we probably mixed a little more oil than was called for.

 

[jjacobs007]

Re: 70 HP Johnson running rough

so your cruising when suddenly it begins to miss,and over heat alarm comes on?then you waited till you got to the pier to check?

 

[tashasdaddy]

Re: 70 HP Johnson running rough

more info. model and year of motor? please. if the alarm went off it was running hot. you need to check compression and spark on all 3 cylinders.

 

[5150abf]

Re: 70 HP Johnson running rough

Ya the weeds on the lower blocked the water flow to the engine and you overheated it, if it is running rough still you probably need a head gasket at the least.

The second that alarm came on you should have shut it off and found out what the problem was.

You need to do a compression check, that will tell you what is going on, all cylinders need to be within 10% of each other.

I would look into this before you run it again so you don't compound any damage already done.

 

[kenmyfam]

Re: 70 HP Johnson running rough

You need to do a quick compression test to verify the motor health. Did all the plugs look the same ???

 

[stelladallas]

Re: 70 HP Johnson running rough

It's a 1993, 70hp Johnson. Yesterday, we did a compression check and all three cylinders read between 105 and 115. All three plugs looked the same to me. We did change and put new plugs in and we are going back to the lake Tuesday. Any advice or anything that you could tell me to check would be greatly appreciated.

 

[stelladallas]

Re: 70 HP Johnson running rough

I still have my problem and to describe it a little plainer, the motor will starts to miss as I come off idle speed. Plain and simple, without getting too techinical and over my head, would the power pack possibly have anything to do with my missing problem? Surely someone out there that owns a 1993,
70hp, Johnson or Evenrude has has this problem and can give me some help. To update what I have already done : new spark plugs, new gas line bulb, checked spark gap, put on one new coil, (unnecessary), removed and cleaned
all three carburetors. I would like to get this thing running right, by the time this heat wave breaks.