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motor cuts out at high speed when accessories are used

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francofroggy

New member
I have twin 454 mercruisers which my starboard engine looses power when I am at WOT and using my accessories.My radio also cuts out.I have changed my battery and alternator on that side and my handheld voltmeter reads 14.2 Volts at the batteries at 1500 RPM.However my dash voltmeter does not read more than 8-10 Volts.Port motor and voltmeter are working normaly. Not sure if its the voltage regulator or corroded wires?
Does anyone have any ideas of how to diagnose
 
Are the batteries individually connected to ground or are they "daisy chained"...? A corroded connection anywhere in the DC voltage feed ( + or -) can cause this, including a defective battery switch. If non marine battery cables were used, check for corrosion at the terminals.... i.e. what BONDO said. Replace any "wing nut" battery nuts with solid stainless nuts (NO NYLOKS!!) and lock washers.
 
sandkicker said:
Are the batteries individually connected to ground or are they "daisy chained"...? A corroded connection anywhere in the DC voltage feed ( + or -) can cause this, including a defective battery switch. If non marine battery cables were used, check for corrosion at the terminals.... i.e. what BONDO said. Replace any "wing nut" battery nuts with solid stainless nuts (NO NYLOKS!!) and lock washers.
Click to expand...

Het sand kicker both batteries are singly wired up to each motor accessories to the starboard engine,port battery to the port engine.Battery switches seem to work but how would I trace a bad ground.In addition radio cuts out if I start the motors or use any power i.e. trims,hatch etc
Thanks for your reply
 
you can test for any bad connection(s) by making a series of voltage drop measurements....assuming you have access to a decent DC Voltmeter. Issues on the return side ('ground') are common, usually due to neglect/bad installations. for most low current connections, you don't want more than 0.1 to 0.2 volts across any connection....
 
Further makomark's post...
1) Get an extension wire ( long enough to reach your dashboard) from the - lead of the volt meter and securely fasten it to the engine block.
2) Measure the voltage at the + terminal of the battery.
3) Then "trace" or follow that lead from there to each place that the +12 V goes in sequence. Per Mako's suggestion, you don't want to see much drop across any connection.

Try this first with the ignition on but engine not running. If you can't find problem, try next with engine @ idle. Candidates for problems include: ignition switch and any crimp terminal, especially it they aren't marine grade.
 
sandkicker said:
Further makomark's post...
1) Get an extension wire ( long enough to reach your dashboard) from the - lead of the volt meter and securely fasten it to the engine block.
2) Measure the voltage at the + terminal of the battery.
3) Then "trace" or follow that lead from there to each place that the +12 V goes in sequence. Per Mako's suggestion, you don't want to see much drop across any connection.

Try this first with the ignition on but engine not running. If you can't find problem, try next with engine @ idle. Candidates for problems include: ignition switch and any crimp terminal, especially it they aren't marine grade.
Click to expand...

Many thanks to all,it was a loose main wire harness on the motor that jiggled loose but was still taped up snugly ,re clamped and power restored !:),unfortunately port motor cut out at high speed soon after at WOT and stopped all power to the coil:mad:
 
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