88 Johnson GT150 firing problem

vp5665900

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Joined
Jun 7, 2013
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2
I have a 88 Johnson 150 on a boat i just purchased that was so say "water ready" it will fire up and run great at idle but when you launch it it bogs when you give it gas. After a little searching with my minimal boat repair skills i noticed that cylinder 2 on one side of the engine and cylinder 3 on the other side isn't firing. boat has new plugs and someone replaced the stater on it recently it still had the repair shop sticker on it. Did some reading online and seem to think it may be the powerpacks but what is the chance of both packs going bad and no allowing one cylinder on each to not fire. is there anything else i should check before dropping the bank on new packs. I also swapped some coils around witch didn't solve the issue so im sure the coils and plugs aren't the problem Thanks
 

multimech

Petty Officer 1st Class
Joined
Apr 26, 2012
Messages
386
Re: 88 Johnson GT150 firing problem

Check your compression.

Check the spark. If you have a spark board, all the cylinders should jump a 7/16" gap with the plugs out of the engine, turning over.

If you have spark on all of the cylinders. Run the engine at idle, in gear (in the water). Pull the plug lead off each cylinder. If it is missing on a cylinder, but you hear the zzzapp of the spark, then try putting your hand over the carb of that cylinder. Does it pick up? If so it is carburation. Rebuild all of them.

If you are missing spark on those two cylinders with the plugs out and on a spark board. Then disconnect the connectors from the packs and inspect both sides of them. All pins in place? All wires in the plugs solidly? If so. Swap the packs. If the same cylinders fail. then I would look to the trigger. Some of these had shared triggers for cylinders.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 88 Johnson GT150 firing problem

You've got some expensive ignition components on that engine. Instead of just replacing everything, check out this website: cdielectronics.com They have some excellent troubleshooting information on that engine. Some of their test involve testing for voltage outputs when cranking. These are good tests, but you'll need a special peak reading voltmeter. Some simple troubleshooting will save you $ in the long run. I'd test/qualify the stator and timer base to start.
 

vp5665900

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Jun 7, 2013
Messages
2
Re: 88 Johnson GT150 firing problem

Thanks for the replys all cylinders have good compression swapped the coils around and now all plugs are firing so I'm guessing it was a bad connection somewhere but now the engine dies when I give it gas noticed I had some gas on my hands when pumping the prime ball and it isn't getting hard any longer so I assume it busted and is sucking air causing the motor to die ordered a new one hopefully after I replace it I'll be rolling on the water
 

Greg_E

Chief Petty Officer
Joined
Feb 17, 2009
Messages
416
Re: 88 Johnson GT150 firing problem

Over time the ground strap on the coil can make a poor connection to the block. When you swapped the coils around it made a better connection and they started working. When you get this sorted out, you might want to go back and clean those connection points.
 
Joined
Feb 17, 2012
Messages
2,906
Re: 88 Johnson GT150 firing problem

look at the primer solenoid is the red lever in auto (in line with the primer body). Then pull the air cover and look in the carbs as you squeeze the bulb if you see gas you need to rebuild the carbs

might be that the plugs were soaked which is why they had no spark
 
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emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 88 Johnson GT150 firing problem

When you prime the fuel hose bulb, it's best to have the bulb oriented upward (arrow up.) If it's laying downhill in the splashwell of the boat, it may not function properly. The ball valves in the bulb do fail on rare occasion.
 
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