2005 F150 4 stroke

[techie89]

I have a 2005 Yamaha F150 outboard that I recently brought in for servicing. The dealer noted a stray voltage that he traced back to the motor. He was reading 386 mV even with the batteries removed. He suspects it is related to the stainless steel prop installed on the motor. The potential was removed by running a ground wire between the engine block and the hull of the boat. It now reads 0 V.

I have a few questions related to this:

1. Should I remove the stainless steel prop and replace it with an aluminum one? Can an aluminum prop be run on these engines as I have heard from different people that you have to run stainless steel?

2. Is this a common thing to have potential created by the outboard? Is it related to the stainless steel prop, and if so what creates it? If it is not the prop, what causes this?

3. The dealer indicated that if left uncorrected, it could cause other electrical problems, shorts, blown fuses, shocks, etc, and possibly corrosion and paint issues. Is this the case or would it require higher potentials than the 386 mV measured?

Thanks

 

[rodbolt]

Re: 2005 F150 4 stroke

need more information, was the test done in the water with a reference electrode, if it was its normal and why you have anodes(zincs) if not done in the water please please find another dealer.
but that is why everything is bonded , to keep electrical potential at 0V or as close as possible, remember 386 millivolts is also written as .386V. a standard LED requires roughly .7 volts and a diode is about .472V just to fwd bias it.
we arnt talking much voltage here and the procedure to test for stray current, using the reference electrode means it has to be in its mooring a minimum of 8 hours and the battery connected.
normal bonding of the engine ground to the hull is done at the battery not the engine block.
so yes, we need more informtion on how and why any tests were done.

 

[techie89]

Re: 2005 F150 4 stroke

testing was performed at the shop, not in water. I have had paint bubbling issues that I have not been able to resolve. While servicing, I asked them to look for any stray current.

 

[rodbolt]

Re: 2005 F150 4 stroke

out of the water(electrolyte) and the battery dissconnected?
I wont believe the stray current thing.
you do as you wish but google about some on stray currents and galvanic corrosion.
that and you cannot measure current with a voltmeter only electrical potention.
need an amp meter to measure current.
where do you keep the boat docked? does it stay in the water?
is it fresh or salt water, remember if you can catch a crab in it its salt.