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  Engine Wiring Harness Upgrade for Diesel Engines

Engine Wiring Harness Upgrade for Diesel Engines

08/22/11

Boats built until 1988 used an ammeter on the engine instrument panel. In 1988 Catalina Yachts replaced the ammeter with a volt meter. Use of an ammeter in the instrument panel required the output of the charging circuit to be routed to the instrument panel then back to the batteries for charging. Wiring harness extensions of varying lengths (depending upon the boat the engine package was installed in) were used to connect the engine to the panel. An eight way push together plug at each end of the Extension Harness connected the engine to the instrument panel. 

 

This wiring scheme was originally created by Universal Medalist Motors who supplied the engine to Catalina Yachts as complete package. The design caused multiple problems for Catalina owners over the years.

 

1) The total wire run was often well over 35'. This long run of small #10 wire meant there was a significant voltage drop between the alternator and the batteries. Additional voltage drop occurred at each plug. With two plugs and a run of wire to the panel and one returning, the circuit passed through four high resistance connections. As a result there was typically significantly less than the usual 14.2 volts at the batteries with the engine running. The batteries never fully charged resulting in a more frequent charge cycle when at anchor.

 

2) Due to inadequate charging, batteries were often left at less than a full charge resulting in shortened battery life.

 

3) A season or two in a salt air environment causes corrosion to the plug connections. An evening and overnight at anchor leaves the batteries significantly discharged. The next morning, when charging, the alternator attempts to push its full capacity through the high resistance connections at the plugs. This heats the plugs significantly and is a potential fire danger.

 

4) If additional batteries or a higher output alternator is added all of the above problems become significantly worse. I was aboard a Catalina 34 with a standard alternator and two group 27 batteries for the house. I am sure I prevented a fire the next morning when, after discovering a smoking harness connector, I switched from the house bank to the single battery engine bank and had the helmsman throttle back. By the time the sails were hoisted the reduced energy through the plugs had let them cool enough they quit smoking. Replacing the harness and connectors with our #Z2758 Engine Wiring Harness Upgrade and #Z2950 16' Engine Wiring Extension Harness eliminated the problem.

 

We use tinned copper wire throughout our Extension Harness. In addition, the ends are individually pre-tinned to provide proper clamping action within the terminal strips. Note that, if your boat is equipped with an ammeter (pre 1988), you will have to replace it with our #Z2652 voltmeter. 

 

Determine in advance of ordering if you will need the Engine Wiring Harness Extension. Remove the engine instrument panel from its mounting location in the engine panel tray. If you can move the panel enough that the push connector is outside of the tray (at least 18" of slack), you have enough length to replace the push connectors with the terminal strips. Carefully inspect the Extension Harness for corrosion. If the harness is in good condition and there is enough slack, and you don't mind tinning both ends of each wire yourself, you will not need to replace the Extension Harness.

 

While the panel is out, inspect the condition of the other components. Check the ignition switch, push button switches and any circuit breakers or alarm module for loose connector tabs or corrosion. If the tabs are not solidly connected to the body of the unit, replace the item now before it fails.

 

Owners of early Catalina 30's find this is a perfect time to move the Engine Instrument Panel up and away from the cockpit sole. By moving it higher, near the top of the coaming, visibility and convenience are much improved. Again, be sure to consider the length of your Extension Harness. If our 16' Engine Wiring Extension Harness is not adequate to reach your desired panel location please call our tech support line at 916/843-1971. As of this writing, 7/21/2011, we carry the 16' length in stock, but we can build an 18' Extension Harness if needed. 

 

And one more thing… The instructions for the Engine Wiring Harness Upgrade mention using the existing #10 charge circuit wire for a short run from the alternator to the starter for a more direct connection to the batteries. Although adequate for the standard installation, many owners have installed a larger alternator or additional house batteries. Either addition argues for an upgrade to a larger wire than #10 to minimize voltage drop and optimize charging.

 



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