problem with Quick Start

I have a 1999 90HP 60 deg Johnson. Over the years I have enjoyed reading this forum and have learned to do a lot of repairs such water pump, fuel pump etc. etc. You guys have been great - thanks. In searching the forum this time I can't seem to find my exact problem and I need some help. Problem - when cold the engine starts good and fast idles good at about 900 - 950 RPM for about 5 sec. then drops down to around 400 RPM and dies unless I choke it and feather the throttle. It used to stay in Q.S. until it reached 105deg. or 1100RPM like it's supposed to. I'm thinking it may be the port temp. switch causing it to drop out of Q.S. too soon . I was just wondering if anyone else has had this problem and how they fixed it. Forgot to mention that once it warms up a little it idles good and runs good.

Disconnect the port temp switch once and see what happens.

Thanks for the reply. I was thinking it may be the temp. switch also. I believe it's the white/black wire that either turns QS on or off - not sure which. Will do some testing when I can get to the boat and get back to you.

Went to use the boat and all of a sudden it won't start at all. I believe it's related to what was causing the Quick Start to act up. It would fire but only enough to kick the starter out. Checked the spark with a screwdriver and it was very weak on 3 cylinders and nothing on the other (don't have an adj. spark tester). Pulled the power pack off and there was a burned looking place on the back with black goo coming out. This is a oem power pack that is less than 1 year old . The previous PP lasted 5 years. I could put a new PP on but what could be causing them to go bad so soon?

I found the old PP that I replaced last year. The motor was running when I replaced it, just not very well. Put the old PP on and it would definitely fire better but still wouldn't start. Didn't want to risk ruining a new PP if there's a short somewhere so I took it to a repair shop. This ign.system is a little too complicated for me. The mechanic was a little puzzled when I told him about the burned place in the PP and said he would test the system. Will post the results when I get them in case anyone else has this problem

Closely inspect the stator under the flywheel to see if possibly a sticky looking substance has been dripping from it down on the powerhead area. If this dripping exists, that would cause a AC voltage drop to the powerpack's capacitor which in turn would result in weak, erratic, and eventually no ignition/spark., In which case, replace the stator.

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If the stator, on the other hand, checks out okay... no cracks/dripping...... Remove the black/yellow wire from the the "M" terminal of the ignition switch.

Now, have a volt meter set so that it would read even the smallest voltage reading and attach the RED lead to that "M" terminal of the ignition switch... the BLACK lead to ground. Observe the meter while turning the key to the ON position (engine NOT running).

If any voltage, even a microvolt appears, that indicates that the ignition switch has an internal short and DC voltage is being fed to the powerpack which will destroy the pack. If this is the case... replace the ignition switch.
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Thanks for the reply. I'll tell the repair shop to check this.

Got the boat back. The repair shop checked the ign. system and found that the power pack and optical sensor were bad. It runs good now but I got to thinking about that black/yellow wire at the PP that joereeves said to check. I disconnected it from the PP and hooked up my digital volt meter between the end of the wire and ground. On the 20v scale I got .oo with ign on and off. On the 2volt scale I got .000 with ign. off but .001 volt with ign. ON so there may be a problem with the switch. Before I go any further, is .001 volt enough to damage the new PP or is it one of the things you have to live with in a humid coastal environment ?

The motor ran good all weekend and the new power pack and optical sensor cured the original Quick Start problem. Life is good again. Mr. Reeves, I was wondering if you could answer my question about the .001 volt on the black/yellow wire at the power pack. The reason I'm hesitant to test it further is because the ign. switch is pretty hard to get to and it's the type where the the lanyard attaches directly to the switch so it's pretty expensive. Just don't want to do all that work if it's not necessary. Thank you

" I was wondering if you could answer my question about the .001 volt on the black/yellow wire at the power pack."

When you say "between the wire at the powerpack"..... If you mean the black/yellow wire that's attached to the powerpack and ground, that won't tell you anything.

f you mean between the black/yellow wire that's part of the engine wiring harness and ground... there's no reason for DC voltage to be present there.

For that test, I use an analog needle meter as I've found a digital meter gives me weird readings.

Voltage To Powerpack Failures
(Magneto Capacitance Discharge Systems)
(J. Reeves)

The usual cause of having those type powerpacks fail repeatedly is having a very small of voltage applied to the Black/Yellow wire (Kill Circuit) at the pack. Test as follows.
Disconnect the Black/Yellow wire at the powerpack.

Insert either a ampere meter or a volt meter set to its lowest DC voltage reading between that Black Yellow wire on the wiring harness side, NOT the powerpack side and ground.

With the ignition key in the OFF position, observe the meter reading. Now turn the ignition key to the ON position and again observe the meter reading.

Any reading, movement of the meter needle, even a microvolt, would indicate that battery voltage is being applied to that Black/Yellow wire. If a reading is present, remove the other end of that Black/Yellow from the raised terminal of the ignition switch.

If the reading ceases to exist when the Black/Yellow wire is removed from the ignition switch, replace the switch. If the reading continues to exist, there would be a short of some kind in either the engine or instrument wiring harness.... to determine which, simply unplug the large RED electrical plug at the engine which would eliminate the instrument cable.

Note that the black/yellow wire must not have any other wire attached to it for the following reason!

Keep in mind that any accessory that has 12 volts running to it, especially when turned on, will have voltage flowing thru it and trailering out thru its black ground wire to complete the circuit. If that accessory has it's black ground wire attached to the "M" terminal that the black/yellow wire is attached to.... you will have voltage flowing directly to the powerpack.

Mr. Reeves is correct. When something like a power pack fails, or any electrical component for that matter, you should determine why. Especially you are on the motor's 3rd pack now.

Thank you for the replies. I'm looking for an analog needle meter and may even invest in a dva meter. Ignition system testing isn't quite as intimidating once you get into it a little. Thanks again.