1988 johnson 120 hp rpm max. 4800

[silverfox1212]

The engine max. rpm reaches only 4800. I thought it is suppose to reach 6000. I decarbed it with seafoam twice. Still no luck. The fuel bulb also is not firm. Cleaned the lines and took air out. Replaced bulb. Stays firm approx. 5 to 10 minutes only. Any suggestions would be appreciated.<br /><br />thanks all.

 

[AntsGrady]

Re: 1988 johnson 120 hp rpm max. 4800

I think the max RPMS also depends on the size of the prop

 

[Dhadley]

Re: 1988 johnson 120 hp rpm max. 4800

Yep. If the motor is indeed healthy then you adjust the set up, including prop pitch, so the motor is able to reach 5800-6000 with your average load.

 

[JB]

Re: 1988 johnson 120 hp rpm max. 4800

Outboard Non-repair topic.

 

[Solittle]

Re: 1988 johnson 120 hp rpm max. 4800

A couple of questions:<br /><br />1. What prop are you running?<br />2. Describe the boat you have it on.<br />3. Where is the cavitation plate relative to the bottom of the hull?<br />4. Have you confirmed that all the plugs are firing?<br />5. What plugs do you have and what do they look like?<br />6. Compression readings?<br /><br />In other words we need more info.<br /><br />P.S. The primer bulb will not stay "hard" for very long after it starts. That is normal.