Voltage irregular

[Lunker Larry]

Hi all. I have a 2005 75hp Yammy with the digital gauges.
Noticed the voltage fluctuating between 13 when *****ing to as high as 16.5 at speed. Battery sits at a perfect 12.4 with the ignition turned off. The charge indicator would also flash. When *****ing it would register about 15 to 15.5 regularly. either way, it was all over the map.
I have a brand new battery.
Any idea what the issue is?
What should I check first?
If repair is needed, can I do it?

Appreciate your time with this.
Regards
Larry

[amahaork]

clean cables ends and apply dielectric compound, check voltage after that. New battery has to be full charged per ampsHours, check voltage after that.

[Lunker Larry]

thanks for the response. Have checked all that. Going to drop it off at the mechanic. need to check the output from the stator as well as the resistance of it that will determine the input to the regulator/rectifier and eliminate that as the problem as well as the gauge in the dash as the culprit. Overcharging is usually an indication of the regulator/rectifier being the issue. I'm pretty good mechanically but just don't have it for electrical.

I'll post a follow up when repaired as there doesn't seem to be too may positive conclusions on all the posts I read on the internet.

Regards,
Larry

[flabob123]

This might help:
I have a 2004 HPDI 150 hp engine. The voltage when crushing back to port was 17 volts. I had a bad voltage rectifier/regular changed it and it fixed the problem.
But don't do what I did .After changing it I started the engine and was reading 12.5 volts . Assumed it was working and went fishing only to have the battery go dead. Opp's I did not hook up one of the ground wires and there was no out put. I was reading the voltage of the battery and not the output of the rectifier.
So good luck and don't forget to hook up all the wires .
Bob

[amahaork]

Larry. Where are you boating? I cannot find US catalogue Yamaha 2005 for 75 HP. Do you wish someone help you, please provide correct engine model, number.

[cpostis]

Larry. Where are you boating? I cannot find US catalogue Yamaha 2005 for 75 HP. Do you wish someone help you, please provide correct engine model, number.

I believe Lunker has a 2005 F75TLRD, US

Give us a shout Larry!

[boscoe99]

75 HP Yam is two stroke motor.

F75 HP Yam is a four stroke motor.

Big difference.

[amahaork]

I only know 2 stroke my Yamaha.
Cannot and will not to say abt F series.

[cpostis]

75 HP Yam is two stroke motor.

F75 HP Yam is a four stroke motor.

Big difference.

Yamaha did not make a US 2005 75hp two stroke. If Lunker's model is a US 2005 75HP, it must be a four stroke model F75TLRD (the only 2005 US 75HP Yamaha made). In fact, 2000 model year was the last 75HP two stroke motor was made by US Yamaha.

Lunker Larry, where are you???

[Lunker Larry]

Sorry all. I was fishing for a week (in my buddies boat) and just got back today.
The motor is a carbed four stroke F75TLRC. That's what is listed on the motor anyway. Heading to the mechanic tomorrow morning.
I'll let you know the diagnosis

[cpostis]

Hope you filled up the fish boxes.
Anyway, an F75TRLC is a 2004 model year.
Please post what the mechanic finds and what he did to correct.
Thanks!

[Lunker Larry]

UPDATE from my mechanic. The first note is his diagnosis and then he went to Yamaha for an answer:

- We looked at the boat on Wednesday and Thursday morning, We could not get the voltage to increase at the dash much over 13.6 volts. We did check AC voltage from the stator and output from the rectifier both with no load and a large load. I got some interesting values very high or what I would consider high coming from the stator and when I confirm those values in the Yamaha manuals they confirm that high values (at the stator) are normal. I have a call into them currently just waiting for some feedback on the actual measurements so I can diagnose which part is the culprit.

-I talked with Yamaha this morning and the manual was incorrect. As it looks right now there has to be a shorting issue happening in the stator that is producing such a high output that would change the voltage erratically coming out of the rectifier which you would see on the gauge as the stator gets hot and cold. I am getting 60 Volts AC coming out of the stator which is nearly double what it should be. So I will price out a stator and let you know, I did also ask them if this could have damaged the rectifier as well and they only would say possibly

I think stators are pricey but what are you going to do. I'll keep you posted.

Larry

[boscoe99]

Why would a mechanic have to go to Yamaha for an answer? I would be wary of a mechanic if so.

The minimum output from the F75 stator is listed as being 98.3 volts. More is better, less is not.

Shorting of a stator typically results in less output voltage, not more.

The F75 rectifier/regulator is known to be problematic. The stator is not.

I suspect that someone is going to have a spare F75 stator on their hands.

[Lunker Larry]

According to Yamaha the voltage stated in the manual is incorrect. The Stator is supposed to put out 30 volts. Mine was putting out double.
Still waiting on the part.

[cpostis]

According to Yamaha the voltage stated in the manual is incorrect. The Stator is supposed to put out 30 volts. Mine was putting out double.
Still waiting on the part.

Here's what LIT-18616-02-70, the manual for your motor F75TLRC says. Seems wrong to me?