Wiring Diagrams

[rbezdon]

I am having an issue with blowing the "ignition" fuse in a 2003 Caravelle with the Mercruiser5.0MPI. I have the Merc Service manuals which show the enginer and trim wiring harnesses but I am looking to find the wiring diagrams for the rest of the boat. It seems Caravelle went out of business and is just in the process of restarting operations so getting documentation is tough. Does anyone out there have a set of wiring diagrams??

 

[Silvertip]

Re: Wiring Diagrams

Boats and power plants are two separate entities and as such you will not find boat wiring in the power plant manual. Nor will you find power plant diagrams in the boat manual -- primarily because boat manufacturers don't produce service manuals and if they did they don't make them readily available. If the ignition fuse is blowing, that's an indication that the problem is NOT boat related since these are two separate electrical systems. Finally, only the power plant, tilt-trim, and instruments are fed from the engine electrical system. All other accessories are fed the the smaller pair of wires on the battery that feed the fuse/breaker panel at the helm. To help isolate the problem, disconnect things one circuit at a time until the fuse no longer blows. That circuit is then the one with the problem. Exactly WHEN or under what conditions does the fuse blow. Perhaps we can help, but not without your detailed input.

 

[rbezdon]

Re: Wiring Diagrams

Well, i spent 4 or 5 hours trying to track down the short blowing the ignition fuse and I am ready to sink the thing. I tried everything to isolate the problem but it is still there.. All I know more than before is the Caravelle fuse panel is powered by the red/purple wire and the ignition fuse is inline with a smaller red/purple which feeds the 12V (always hot) connection on the ignition switch. The ignition switch has 5 wires where as the Merc drawing has 3. the red/purple for power in, the purple which is the switched 12V for powering all of the boat and engine, the yel/red for the starter solenoid The other two are purple/ white connected to purple and a red which is 12v switched on just like the purple but when the switch is turned off it drops quickly to like 6V then drifts very slowly down.

Since the purple is the main feed I assume the overload is on that line but there are literally dozens of purple connections. If I turn the ignition to on all of the purple and red are energized and the fuse does not blow. Even leaving the ignition in the on state for 10 minutes or more, everything is fine. Start the engine and in about 2 to 5 minutes the fuse blows, even a 30AMP. Replace the fuse and all OK for another go of about 2 to 5 minutes with engine running. I tried running trim up down and turning the steering while running trim and no fuse blowing. Fuse blows when engine is running in neutral or in gear. I cant figure out what else kicks on when the engine is running that is not powered with the ignition "on". any ideas??

 

[rbezdon]

Re: Wiring Diagrams

Also made some other measurements. Voltage with ignition on and engine not running=12.65 no AC. Makes sense as this is battery voltage. Voltage on purple with engine running 13.86 with no AC. This seems a little low to me as I thought charging float voltage should more like 14.3V. I did also try pulling all of the fuses in the helm mounted panel and the ignition fuse still blew out. since the remaining equipment is not run from the ignition fuse (radio, trim, blower, horn, bilge pump, anchor/nav lights cigarette lighter as I can remeber off of the top of my head) and all of those operate fine after the ignition fuse blows, I am sure the problem is in the engine (power plant). Basically, since most all of the other equipment operates after a blown ignition fuse it can not be my problem. When the ignition fuse blows the oil press, batt volt, fuel, tach etc all go dead and the engine quits. Since it is not possible to disconnect or isolate the charging, Ignition and Fuel circuits and run the engine, i am unable to further isolate the problem.

 

[Silvertip]

Re: Wiring Diagrams

The problem is apparently in the ignition system so the coil, ballast resistor (separate resistor or resistor wire if it has one), electric fuel pump if it has one, electric choke coil if it has one, or even the alternator itself could be the culprit. In other words anything that becomes active when the engine is running is suspect. Remember, if you have an electric fuel pump, that won't be running until the engine builds oil pressure so just because the key is on, the pump will only run for a few seconds, then shut off.

 

[rbezdon]

Re: Wiring Diagrams

Yes, I have switched on the ignition and the fuel pump runs for a few seconds and stops, never blows fuse. It is a 2003 5.0 MPI so there is also the high pressure pump for the injectors but I am not suspecting that becasue the engine runs for several minutes with no issues. Also, it has an electronic ignition and an ECU control computer. I have no way to check and see if the ECU has any fault codes.

All together, I am leaning toward the alternator yet I have a fairly extensive auto experience and I have never seen an alternator take out a dash fuse before. The alternator output ties directly back to the battedry before the dash fuse leaving only the sense wires but one of thoise is purple power so I guess it may be possible. The other thing I noteds above is it seems to me that the charging voltage at 13.85 is a little low. This may also point to an alternator problem. I'd change it in a heartbeat if it were a car but the Marine versions are really out there in price just to change it as a way of elimination possible faults rather than a true diagnosis.

 

[Silvertip]

Re: Wiring Diagrams

In your original post you said it was an "ignition fuse" that was popping. In your response to my post you said you never saw an alternator take out a "dash fuse". Keep in mind that most boats have the helm powered via the engine harness. Gauges would be on that circuit. If you have a red/black pair of #8 or #10 wires runnning from the battery to the helm, then those wires would power the fuse panel and all other accessories.

 

[rbezdon]

Re: Wiring Diagrams

Yes, i agree and that is the case here. I referred to a dash fuse in reference to my automotive experience. The fuse i am blowing in the Caravelle is labeled "ignition" and it connectes sirectly to the ignition key switch. it is powered by the #10 red/purple wire and a smaller size red/purple runs from the fuse to the ignition switch at the continuous 12V contact. Since this appears to be the only connection from the fuse panel fused side of the ignition switch, the over load must be comeing through the ignition switch. The switched side of the ignition sswitch connects to the purple connection back to the engine connector through the lanyard switch. unfortunately, there are two other wires connected to the ignition switch, a purple/white and a red, which I do not know where they go. The purple/white is connected to the same switch terminal as purple and the red is connected to another switched pole on the ignition switch. This is why i was looking for a wiring diagram of the BOAT side of the electrical system. It is easy to get the Merc diagrams but not easy to get the Caravelle diagrams.

 

[rbezdon]

Re: Wiring Diagrams

Good News, problem solved. My son found a pinched wire where the help control clamps to the steering cable under the dash. it was the purple/white which seems to be the boat side of the ignition switched 12V main power (purple with no stripe being the engine/power plant side of the ignition switched 12V main power). Spliced out the pinch and all seems OK now.