engine dies intermittently as well all gauges for port engine

[Jeff D]

HI members, i hope someone can help. I have a 1988 300 weekender w/twin 5.7l mercruisers and Borg Warner velvet
drives. intermittently i am having port engine failure. this happens at idle as well at any speed. when this happens all
dash gauges for port engine stop working as well. when i try to restart engine there is no gauge activity and engine does
nothing. all my batterys are new as well as new ingition switches. when engine does run it runs great w/no problems. i suspect possible electrical failure of some kind, but don't know where to start diagnosing problem. also this problem is not heat sensitive. meaning problem happens w/both cold or hot engine. i don't have any wiring diagrams, and do not know if gauges get there power source from ing.switch or starter motor solenoid etc. any help would be great. thanks Jeff D.:huh:

 

[fwebster]

I can get you started..........

You are losing the 12V supply to the main ignition circuit on the dash. That is about the only thing that will intermittantly affect the gauges and ignition. Don't mess with the solenoids, starting circuit etc. You either have a bad starting/ignition switch or your boat has several different wiring harnesses on it. The engine harness is connected to the bulkhead harness, it is connected to the instrument panel harness. All are connected with plugs. Somewhere in the 3 harnesses, the main 12V wire for the ignition is not making contact. This is usually caused by the pins in the plugs coming unseated and backing away from its counterpart on in the other plug. First, you need to find all the plugs then pull each apart and examine the male and female parts. Find the pin not making contact and push it back into its place.

Good luck with it.............

 

[Late Again]

Just experienced the same problem only with the starboard engine. Drove me nuts for two weeks on a 900+ mile trip. Engine would start and idle fine and work at low speeds with no problem.....once leaving a marina and trying to get on plane the engine would cut out or quit completely. After tinkering with the engine switches or checking wiring around the engine it would start and run fine for up to five hours. Finally one morning none of the gauges on that engine worked and after checking again found a loose connection on the main wiring harness on top of the engine. When checking the wiring, the ignition rocker switch at the helm was on and when I touched the loose connection the alarm that usually sounds when first turning on the ignition went off. Seperated the connector, spred the contacts a little, reattached and tightened the screw and it was boating fun again.......that loose screw and connection that wiggled when moving darn near drove me nuts!!!!!:smt021

Late Again
2000 310 Sundancer
350 Mag Horizon
Velvet Drives