1991 90HP won't idle

Chun-Mu

Cadet
Joined
Oct 30, 2005
Messages
15
Hey guys;

I have a wierd one (again)
Boat ran strong the whole weekend. When we came home my father crossed the battery connections when flushing the engine. the price we had to pay is that the engine wouldn't start. I swapped the powerpack with a spare I had. It started right up with the high idle. Now it won't idle. This baby used to purr like no other motor :'( well maybe like a 4-stroked:)

I tried it out this week and it runs fine; it's the idle that's gone. I have to throw it in gear while in the high idle (1000RPM; I know this is bad for the LU but just wanted to see if it works in the high RPM's as well)
I'm suspecting a bad powerpack cause this is the only thing I swapped.

Please state your comments,
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,544
Re: 1991 90HP won't idle

Well, beins you were doing fine and all of a sudded have these problems, go looking for what gets mad when you reverse power leads; obviously an electrical problem.

One place is the alternator's rectifiers. Usually an alternator has a pair of diodes for each stator winding which full wave rectify the alternating power into direct current, which the battery requires.

In looking at my service manual, which only goes back to the '97 there is no separate rectifier pack. Looks like the rectifiers are built into the voltage regulator module. It bolts onto the electrical plate with 2 screws and is an epoxy filled plastic container; probably about 1" or so square with 2 mounting ears on it.

The wiring diagram shows 6 wires to the unit (2 yel, 2 red, 1 gray, 1 black). The red leads are the 12v outputs to the battery and the yellow are from the alternator. The black goes to ground and the gray goes to the remote control.

Since it runs ok at higher rpm's you have to suppose that the 3 cylinder firing modules and the trigger which triggers them are working ok.

Otherwise there isn't anything that cares which direction current is going.

Normally one of the pair of alternator rectifiers (per stator winding) has the cathode tied to the 12v output lead and the anode tied directly to ground.

If you reverse voltage this, there is no resistance in the circuit and you will fry the diode; one for each circuit .

HTH.

Mark
 

Chun-Mu

Cadet
Joined
Oct 30, 2005
Messages
15
Re: 1991 90HP won't idle

I will ohm test the rectifier to see if this is my solution;

I will post my findings as soon as I can

thanks,

Chundriss
 
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