1988 Johnson hot & rough

[olm]

I have a johnson 1988 120hp replaced water pump& thermostats. water still comes out very hot out of the tale-tell & spirts like if air were being pumped through, runs ok at high rpm but very rough at idle & midrange. compression is 120-121 all around.just got boat. don't know history looks very clean, does not look like a saltwater motor. If anyone could help would be apricciated

 

[dcolpitts]

Re: 1988 Johnson hot & rough

welcome,check the compression at all the cylinders, they should be within 10% of each other @ about 125psi. If not It sounds like a head gasket leaking water into one or more of the cylinders. check search at the top of the page, there have been several posts on this topic. Good luck

 

[olm]

Re: 1988 Johnson hot & rough

I have changed the complete water pump including the impeler, I might have twistid it the wrong way installing the cap. would that do it? Im not looking forward to dropping the lower unit again. worked on Yamis before this is my first johnson and the shifter rod gave me fits trying to restab.

 

[93bronco]

Re: 1988 Johnson hot & rough

i would retorque cylinder heads bolts as labeled on head-the # sequence 1-14(20-22 ftlbs) and also retorque the powerhead to adapter housing bolts/nuts. (10 bolts & 3 nuts, 144-168 in.lbs)<br />-<br />sea if that helps before you do anything else.<br />-<br />the shift rod is easy if you remove the lower cowl, and disconnect the shift cable.

 

[olm]

Re: 1988 Johnson hot & rough

thank you gentlemen for the advise. since i have this wealth of knowledge at my fingertips. i would like to pick you brains on ohter troubles i have with this motor. It starts and runs fine out of the water but deosnot like to start in the water. Idles very rough with alot of spiting and really sputters to get to plane. Once at about 4000 rpm smoos out and runs fine all day.<br />is this carbs?

 

[Solittle]

Re: 1988 Johnson hot & rough

Crud in the carbs will result in what you describe. Your homework is:<br /><br /> http://www.outboardrepairs.com/carburetors/

 

[93bronco]

Re: 1988 Johnson hot & rough

check and clean all recirculation fittings and valve.<br />along with the carbs, it will run better.