What do you experts think???

[GSMAN]

Bought a used Hydrasport rig with a 1994 200 HP Johnson Ocean Runner last February. I had the motor thoroughly checked out by a professional mechanic and was given a good clean bill of health. Good even compression and no electrical issues. Rebuilt the carbs and put new sparkplugs. The VRO is unplugged so I have been pre-mixing the oil. Anyways, used the rig a couple of times this summer and maybe put around 20 hours on the motor. Here's what happened. Went offshore last week to a rig around 20 miles offshore. Motor started up fine, smoked as usual, and reached our destination with no problems. Motor ran fine. Caught a mess a fish and it was time to head back in. Unhooked the boat from the oil rig and started back. Around 1/2 mile from the rig the motor shuts down. Put it in neutral try starting it up runs for maybe a couple of seconds put it in gear and throttle up and it dies. Repeat this same process and the same thing occurs. The following day I attach the "rabbit ears" to the motor and it pretty much did the same thing. It fired but would not run. Took it to the mechanic and he decarbed and replaced the spark plugs. He also checked out the electrical system and said it was firing just fine and pretty much compression was fine. After he decarbed and replaced the sparkplugs he fired it up and the motor ran fine. He put a load on it in the water and ran it at 3000 to 4000 rpms for about 30 minutes and the motor didn't miss a lick! My question is can sparkplugs foul up that quickly and cause the motor to shut down while you are running at high rpms? Any input would be appreciated.<br /><br />Thanks!

 

[rodbolt]

Re: What do you experts think???

not normally<br /> sounds like you had another issue going on.

 

[Joe Reeves]

Re: What do you experts think???

The fact that the engine ran fine after your mechanic installed new spark plugs indicates that the plugs were possibly fouled, but something caused those plugs to foul.<br /><br />The most likely component to cause that would be a failing stator or a intermitent short in the ignition switch.<br /><br />The ignition switch can be checked by simply removing the Black/Yellow wire for the raised "M" terminal of the switch when the problem occurs. If the problem vanishes when that wire is removed, replace the switch.<br /><br />Note that the engine cannot be shut down by turning the key off when that wire is not connected.<br /><br />The stator (under the flywheel) is a two fold component. A series of small coils supplies AC voltage for battery charging purposes. There are also two large black coils within the stator that provides approximately 300 AC volts to the powerpack. When the stator starts to fail, it may supply the proper voltage to the powerpack when cold, but when hot, that voltage will drop which results in erratic weak ignition, and eventually no ignition/spark.<br /><br />Normally (but not always) when the stator starts to fail, those two black coils will start to melt down and will drip a sticky substance down on the timer base and block assembly. This can usually be seen easily with a good flashlight.<br /><br />There may be some other issue creating your problem, but these two mentioned areas would be my starting point.

 

[rodbolt]

Re: What do you experts think???

another problem that can cause goofy things is loose flywheel magnets. that can be inspected with the same flashlight when looking for oozing charge coils.

 

[Dhadley]

Re: What do you experts think???

What spark plugs are you using?