F100 Overcharging

[Bill]

I have a 2000 F100 and the voltmeter has recently started pegging to the full stop beyond 16V when I am at normal operating speeds (>4000 RPM). Prior to this, the voltmeter was normally between 14 and 15 at those speeds. I took the motor to the dealer, and the mechanic said that the F100 has an unregulated charging system and this is normal. He said he got this information from the Yamaha service rep. The mechanic could not explain why it has just started doing this, or why the parts catalog lists a Rectifier-Regulator assembly.

Has anyone seen this before? Is the mechanic correct, and I should ignore this? If I change out the rectifier-regulator assembly, will that correct the problem?

[boats.net]

Yes it will show high voltage on voltmeter, it's not a full regulated system, however if you check the voltage at battery you will see it doesn't get that high.

[Bill]

I consulted with a mechanic from a different Yamaha dealership. He said that while an occasional spike in voltage is not a problem, constant readings of over 16V is an indication of a malfunction. He said that they have replaced several rectifiers in his shop, and some had been so overheated that they were partially melted.

He suggested that I check the voltage output with a handheld meter and confirm the reading that I am getting on the analog meter that came with the boat. If the high reading is correct, then I should replace the unit.

When I checked the Boats.net Yamaha parts catalog, they did not list the F100 on the 2000 model year page. The 1999 and 2001 pages list the same part number (67F-81960-11-00) for the rectifier/regulator assembly on the F100. Can I use this part number for my 2000 model?

[boats.net]

Yes 67F-81960-11-00 is the correct part number for 2000 F100 engine

F100 overcharging

I had the same problem, the volt meter jumped to 18 volts. I replaced the volt meter and it went back to 14 volts for 2 weeks.. Now it is reading 12 volts never goes above that. I beleive it is the rectifier. Mine is a 2000, F100 same as yours.

[boats.net]

Probably is a bad regulator, Test the regulator and wiring connections at regulator. Check that battery cables connections are clean and tight.

Under chargint

I checked the battery connections and they are good, I am not sure where the regulator is? The other comments stated it is an unregulated system? Is it regulated or not? Thanks Frank

[Yokozuna]

I have 2005 F100 TLR and I'm looking for the new rectifier/regulator...Does anyone know correct part number?

[rodbolt17]

the system is a regulated system.
the regulator/rectifier are one unit.
typically bad battery cable connections cause them to fail.

[Searider]

I am not sure where the regulator is? Frank

Look at the front of the engine . It is located below the CDI . You have to remove a plastic cover to get access .
Cheers .

[BQUICK]

Look at the front of the engine . It is located below the CDI . You have to remove a plastic cover to get access .
Cheers .

Also, check your battery. I had a high voltage issue (15+) and the battery was low on water/acid and even with the motor shut off was getting higher than normal readings. 13.2-13.5. Normally a battery, fully charged but not charging will show no more than 12.5.