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Merc 90 ELPTO Charging Problems

F

fishrman

New member
I have a Mercury 90HP ELPTO S# OT816037 on my bass boat which was acting strange at the end of last year. The dash voltmeter would drop to ~12V at higher speeds, say >4000rpm. When I slowed to <4k, it jumped up to14-15V. This got worse until the end when it would only charge at <1200rpm. Also, when not charging, the dash gauge would pulse at a ~1/sec frequency!!!!

This year I looked at it more closely and measured ~35V at the stator input wires of the voltage regulator, using a digital voltmeter. The regulator output measured a constant 12V. Believing the regulator was the problem, I replaced it (Part #883072T) BUT the readings did not change!! For what its worth, I also measured the voltage at the dash with the DVM and it varied from 12 to 13V at variable rpm.

Does this make sense to anyone? Has anyone heard of a pulsating dash voltmeter? What would you suggest I do next, find a repair shop?
 
After getting no response here, I contacted JustAnswer's expert. He said the 42ohm reading I got on both the new and old diode was outside the range 100-400. The diode does not have enough bias in 1 direction. What would happen is it would leak AC to the battery. The battery would be getting DC and AC to it at the same time. That explains your pulsing at the dash as well.
Also my reading of 35V with DVM, not a DVA, indicates too high a peak voltage which could break down the diode. Broken magnets could be producing more +/- poles which could produce the higher voltage....
So I guess the 'fix' is waiting in line at the local repair shop.......
 
I kind of thought there was a diode problem w/a puslating DC voltmeter. If the diodes(s) are not a one piece bridge rectifier have the shop replace all of them; you don't want to be back for a similar problem when another diode fails.
 
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