3.0 mercruiser ignition problem

[bill k miami]

my 1999 bayliner/3 liter mercruiser ignition fuse blew under load in biscayne bay. the motor runs fine at idle with out load in my driveway but under load traveling about 35 mph the motor kept on shutting off. everytime i would replace the fuse it would blow in the next few minutes. the fuse that blows goes from the fuse panel to the battery terminal on the key switch. the motor has new spark plugs, wires, dist cap and rotor, and a new alternator. at home the fuse did pop a few more times while trying to start. the motor just did not have enough fuel in the carb to start so it would sputter and the fuse would blow.after the motor seemed to have enough fuel in the carb it started right up and ran fine. i reinstalled the old alternator and it seemed to run fine as well. the guage reads 14 volts while the motor is running. the new alternator and the old alternator seem to have the same voltage reading while the motor is running. all the wireing seems fine and there are no kinks in the wiring. help!

 

[Don S]

Re: 3.0 mercruiser ignition problem

Where is this fuse located? Is it the main circuit breaker on the engine, or a fuse under the helm. If under the helm, what color and size wire is it in, and what size is the fuse?
Just an FYI, the fuses on the engine and at the helm have nothing to do with spark plugs, caps, rotors, alternators etc. but they do provide power to the ignition system so it can work. They also control the amp draw in the system, not the voltage.

 

[bill k miami]

Re: 3.0 mercruiser ignition problem

Where is this fuse located? Is it the main circuit breaker on the engine, or a fuse under the helm. If under the helm, what color and size wire is it in, and what size is the fuse?
Just an FYI, the fuses on the engine and at the helm have nothing to do with spark plugs, caps, rotors, alternators etc. but they do provide power to the ignition system so it can work. They also control the amp draw in the system, not the voltage.

the fuse is under the dash. a hot wire goes into the fuse panel. from there wires go to the lights, horn, etc. the one fuse that was popping is an 15 amp fuse supplying the battery power to the key switch. it only blew under load at sea going about 35 mph. i would replace the fuse and it would pop a few minutes later. in my driveway the fuse will not pop while starting or running at any rpm. the tach and eng temp guage also are eratic. i replace all gauges except the mph and tach. all are tied into the ignition system via a purple wire. the color of the wire from the fuse panel to the battery switch terminal of the key switch is red/purple. thanks

 

[tommays]

Re: 3.0 mercruiser ignition problem

With the strange guages i would unplug the wireing harness plug at the engine spray some contact cleaner on the connections and plug it in again

i had a voltage drop at the dash and a bunch of jumping guages that traced out to the plug


Tommays

 

[Don S]

Re: 3.0 mercruiser ignition problem

In the Mercriser manual for your 99 model, they don't even show a fuse in the red/purple wire, but in the older models they did have a fuse, and it was a 20A.
Does your engine have a circuit breaker mounted on it? It will have a red push button.