70hp Boat at 17 Volts!

Matthew K

Matthew K

Line Up and Wait
Joined
Sep 14, 2016
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Location
Georgia
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Broke Engineer
Hello all!

I'm staying at a relatives cabin. With their permission, I took out their 70hp outboard boat(I've taken it out many times before.) This time though, I brought my handy dandy cigarette outlet volt meter with me.

After getting to about 4500rpm, I noticed the voltage was in the 15s, then, it got up to 17v and stayed their unless I went to idle at which it stayed about 15.5 volts. The built in volt meter stayed at the same spot no matter rpm. I know this can't be good at all for the battery, but I don't remember the volt meter being any lower than it was this time, so I imagine it's done it for a long time.

I imagine the rectifier is shot. I'll have to tell my relative about it when I get back I guess. Anyone know how hard it is to replace?IMG_20161124_140648910_HDR.jpg IMG_20161124_141721645.jpg
 
Check the battery first.

What is the gauge under the volt meter?
 
I've run into a couple 80's vintage outboards that would overcharge like that when hooked to an AGM battery, but be fine with a regular flooded cell battery. Both times it was inline Yamaha outboards.

Depending on what motor you have the regulator/rectifier may be water cooled. If not it's a super easy change on most.
 
Are we sure it actually has a regulator of any kind and doesn't just have lighting coils with a rectifier and relies on the battery to keep the voltage in check?
 
Capt. Geoffrey Thorpe said:
Are we sure it actually has a regulator of any kind and doesn't just have lighting coils with a rectifier and relies on the battery to keep the voltage in check?
Click to expand...

No we aren't. But it sure doesn't appear to be a faulty rectifier. It may be doing exactly what it was designed to do.
 
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