What's wrong? - 1990 Johnson 120

[sunbird1]

The engine is running great but the problem is one head stays cool while the other reaches normal temps. Also, I pulled the plug wires off plugs on the cold head and there was no change in idle. When I pull them off the other side the engine runs rough. What makes this more confusing is the problem is intermittent. When I run on the muffs to test before I go out everything is fine. When I get back and flush the engine the problems start. Any ideas on what to check next?

 

[93bronco]

Re: What's wrong? - 1990 Johnson 120

have you checked your tstats, do you have the black ones, and are they complete.<br />were they seating rite in head.<br />retourqe heads.<br />you could also have a power pac malfunction dealing with the Quickstart.<br />or a problem twith the water control valve.<br />get some thermomelt stix 125 & 163, or a digital pyrometer.<br />that should get you started

 

[sunbird1]

Re: What's wrong? - 1990 Johnson 120

I replaced the thermostats already and that didn't make a difference. I'll check the manual regarding testing of the powerpacks. Thanks

 

[93bronco]

Re: What's wrong? - 1990 Johnson 120

i know the 1st time i had a intermitent problem with with cylinders going in & out it was the powerpack.<br />it could also be the coils, its has been suggested to use a hair dryer to heat them up to sea if they are breaking down when hot.<br />-<br />you could also try switching coils from 1 side to the other to sea if problems follow.<br />-<br />found this old post sounds just like your problem.<br /><br /> '90 J120hp loses power' <br />hope that helps.

 

[angus63]

Re: What's wrong? - 1990 Johnson 120

Does your model have a shift switch that cuts out half of the cyls when shifting? If so, have you checked it out?

 

[sunbird1]

Re: What's wrong? - 1990 Johnson 120

I don't know if it has a shift switch, I'll check the manual. If the powerpack was bad though would the head not get hot? That is what has been confusing me because I originally just thought is was a sticky thermostat.

 

[angus63]

Re: What's wrong? - 1990 Johnson 120

No fire= No heat

 

[sunbird1]

Re: What's wrong? - 1990 Johnson 120

Thank you guys for your input, I really appreciate/need the help. One more question, I was reading the link that 2K Boat attached and that talked about a power loss because of the faulty powerpack. I have not noticed any power loss. She runs the same as always. If it wasn't for the cold water coming out of the pisser I wouldn't have noticed anything at all.

 

[KillerJello]

Re: What's wrong? - 1990 Johnson 120

sounds like a misfire to me if you pull that plug off and it doesnt run any rougher... possibly been misfiring since you bought the boat since you havent noticed a loss of power?

 

[93bronco]

Re: What's wrong? - 1990 Johnson 120

the other thing you mite want to check is the water control valve on the throttle arm.<br />its used to send water to the tstat diaphram to keep tstat up against donut seal below 2000 rpm.<br />it could be blocked with debri & not allowing it to maintain pressure.<br />its easy to take apart & clean.

 

[sunbird1]

Re: What's wrong? - 1990 Johnson 120

Thanks 2K Boat, I'll add that to the list this weekend. I just bought a compression tester, last night. I'm going to check that too. I'll keep you posted.

 

[Joe Reeves]

Re: What's wrong? - 1990 Johnson 120

Sunbird.... It's always possible that a new thermostat could be faulty. Switch the entire thermostat housing assy netween heads to see if the problem also switches.<br /><br />Are the springs within the thermostat housing the same? Is it possible that one of the diaphrams that the thermostat housing screws into is backwards? (don't recall if that's possible or not but it's worth looking into).<br /><br />The head that's running cold.... Is the thermostat seat/seal secure and exactly where it belongs (compare with the other head).<br /><br />You say that when you pull the plug wires off of the head that's running cold, there's no change in the rpms, but when you pull a plug wire off of the other head, it runs rough? If that was indeed the case, when you remove the plug wire from the warm head, the engine would be running on one cylinder which is impossible. Remove both wires from the cold head..... what happens?<br /><br />If the thermostats prove to be okay along with their related springs, seats, etc, it would seem likely that the problem on the cold bank is ignition related. When this problem takes place, remove the spark plugs (all), rig up a spark tester of some kind whereas you can set a 7/16" gap, then crank the engine to observe the spark.<br /><br />The spark should jump that gap with a strong blue lightning like flame (really a strong snap), not a flimsy shinny thread like spark. Let us know what you find.

 

[sunbird1]

Re: What's wrong? - 1990 Johnson 120

Thanks for your input Joe. I was hoping you would provide some insight as well. I will try and test everything this weekend and post the results on Monday.

 

[sunbird1]

Re: What's wrong? - 1990 Johnson 120

UPDATE: I did some testing this weekend and these were the results.<br /><br />Compression - 120 on all cylinder (very happy about that)<br /><br />Coils - switched coils from port to starboard and no change. I think the coils are ok.<br /><br />Powerpack - didn't do an output test yet but noticed that the pink with white and purple with white wires had frayed and alomst broken, insulation was melted. I just put some electrical tape on them and ran the engine - no difference. Should I change the pack anyway?<br /><br />Spark - could not jump a 7/16 gap on any cylinder. However, there was an orange spark on all cylinders. Is this the problem?<br /><br />Plugs - noticed that 3 of 4 plugs were clean/not fouled. Only the plug on the top right (non running) cylinder was dirty.<br /><br />Any ideas what to test next? Thanks

 

[Joe Reeves]

Re: What's wrong? - 1990 Johnson 120

Sunbird.... You stated: "Spark - could not jump a 7/16 gap on any cylinder. However, there was an orange spark on all cylinders. Is this the problem?"<br /><br />That is definitely a problem but whether it is your sole problem remains to be seen, however it is one that must be corrected first.<br /><br />NOTE that the spark test must be performed with the spark plugs removed in order to obtain the highest cranking rpm possible. If you left the s/plugs in, remove them and repeat the test.<br /><br />If the spark is still orange (no good), look under the flywheel (better to remove the flywheel) to inspect the stator assembly which is the beginning of the Charging and Ignition System.<br /><br />The small coils on the side of the stator are AC battery charging coils, and the two larger black coils (visible) at the rear of the stator on a 35 ampere system, and at the front and back on a 3/9 ampere system (sealed in), generate AC voltage to energize the powerpack. The stator runs very hot and may have started to melt down at those black coils. This would cause a sticky substance to drip out of those coils down on the block and timer base.... a sure telltale sign of stator failure that would affect the ignition system.<br /><br />When installing the flywheel, be absolutely sure to torque the flywheel nut to 145 foot pounds, otherwise the key will shear causing damage to the C/S and flywheel tapers. Keep us informed.

 

[sunbird1]

Re: What's wrong? - 1990 Johnson 120

Thanks Joe. When I did the test, I used a spark tester that plugs in the wire and then attaches to a ground. We did it with all the plugs out and then with the plugs in and the wires off. There was no difference either way. Next step will be to pull of the flywheel. I'll keep you posted. Also, I noticed that the battery isn't charging like it used to, in fact when running at idle the volts were fluctuating between 11.7 and 12.1 volts. I run two batteries and they usually run 12.3 at idle.

 

[93bronco]

Re: What's wrong? - 1990 Johnson 120

not stepping on any toes.<br />-<br />you said 'spark checker' as in one?<br />doing one at a time?<br />or did you do all four at the same time with the stevens S48H/S48 or something similar?<br />-<br />i believe you have to do them all at the same time to avoid damaging the PP and possibly the timer & stator.<br />or have the plug wires grounded.<br />-<br />i did a search on how to make one since i cant find my new stevens S48H ( think it got thrown out by mistake )<br />and have made one similar to the one in this post below that rowhome suggested. <br />spark checker <br />i still have to do the ground wire, but if it works- it only cost me $2 for the screws i wanted, everything else i had around the house + my time.<br />-<br />if you did all four at the same time or the left over ones grounded disreguard.<br />just trying to help.

 

[sunbird1]

Re: What's wrong? - 1990 Johnson 120

I did it one at a time. I bought the spark tester from autozone. First I hooked up the tester to one wire and left the other 3 attached to the plugs. Did not see any spark, let alone jumping a 7/16 gap. Next I removed all the plugs, but did not ground the wires and still no spark. Finally, I just tried testing the spark with a screwdriver in the wire holding it near the plug. This is when I saw an orange spark. Was this a sufficient test? Or do I need to test them all at once?

 

[Joe Reeves]

Re: What's wrong? - 1990 Johnson 120

Sunbird.... Your method of testing is sufficent and no harm will be done to any of your electronic components. It's nice to have the proper test equipment to speed testing along, but it's not necessary. Continue to your inspection of the stator.

 

[Solittle]

Re: What's wrong? - 1990 Johnson 120

I built the homemade apark tester referred to by 2K & it works fine - looks crappy but didn't cost a dime.