1993 120 johnson looper-HELP

H

holiday1

Cadet
Joined
Aug 2, 2009
Messages
7
I Have A 120hp Johnson And Took It Out Ran Perfect At First But Then It Loss Power And Would Just Bareley Plane Off About 30 Mph With No Power ,when Returned Home Ran A Compression Test And All 4 Cyl Hit 135lbs, Started The Motor And It Was Running Rough And Unplugged Each Plug Until On The Bottom Left Cyl Seemed Like It Would Fire Sometime And Not At All Or Weakley. I Replaced All 4 Coils With New Coils And New Plugs And It Started And Ran Great.we Took It Back Out To The Lake And At First Ran Great And Hit 45-50 Mph No Problem , At Which Point I Let A Wakeboarder Out When I Hit The Throttle To Pull Them Out Of The Water It Suddenly Started Acting Like It Did The Pror Week Witn No Power And Running Rough Maxing Out About 30 Mph, Could This Be A Power Pack Or Is There Floating Debris In Carb-help I Am Lost
 
J

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,198
Re: 1993 120 johnson looper-HELP

holiday1 said:
Could This Be A Power Pack Or Is There Floating Debris In Carb-help I Am Lost
Click to expand...

Could be, could be a lot of things so you need to perform a couple of troubleshooting tests that will help sort out the symptoms.

Compression is good.
First be certain the alarms all function, touch the heat sensor wire to the block, it should beep,
if not , fix it before doing anything else.
It could be overheating and going into slow mode.

Next buy a $10 spark gap tester and set the gap at 3/8th inch, with all sparkplugs removed see if it jumps the gap, if no then its ignition.
Likely culprit is powerpack.
If yes then its likely to be fuel delivery,,,,unless the problem is intermittent?

In which case take the tools out and do the tests on the water, a timing light is usefull to show whether its getting spark on the water although it will not show spark strength.

Next test, when its bogging down pump the fuel bulb and see if it perks up, if yes then its the pump. Check for leaks around pump.

When its running press the choke, it should bog down ( too rich), if yes then its good.

If you want to test the powerpack before replacing you'll need a peak reading meter, ebay $70.
http://cgi.ebay.com/ebaymotors/Mari...emQQimsxZ20090802?IMSfp=TL0908021310003r31899

auction is over but contact seller if you want one. Neat tool to have in your box.
 
tashasdaddy

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 1993 120 johnson looper-HELP

here are some test. is the vent open on the fuel tank, does the fuel line bulb go flat? does pumping the bulb, correct the problem? also check spark immediately when it acts up, could be a coil or power pack heating up and failing. trouble shoot, do not throw parts at it.
 
H

holiday1

Cadet
Joined
Aug 2, 2009
Messages
7
Re: 1993 120 johnson looper-HELP

when first started acting bad a couple of times acted lik it was going to run good but then go back to the way it was running -bad. it has a 18 gallon above deck but permanant tank with new gas line and vented through hull, the priming bulb stays firm, but boat sit up anbout 2 years until recently when took on 2 week vacation ang 3-4 times out to the water and ran fine till last two timesand last time after putting new coils on it ran probably 10-15 mins before trying to pull a wakwboarder and it started acting up
 
You must log in or register to reply here.
Top