78 Johnson 115 Overcharging??

[phx5kegsman]

Took the (bass) boat out yesterday and motor was running good. The voltmeter was reading between 13-14.9V for most of the day. I never opened her up to WOT and cruised at about 4500-5000 rpm. Then on my way in the voltmeter was reading a steady 16.7V and even went all the way to 17V for about 30 seconds! I've replaced the rectifier on this motor several times. In fact, EVERY electrical component has been replaced. Before I go through all of the test procedures in the manual, I thought I'd ask for some input here. Has anyone here ever had these high voltage readings? Could this damage my motor. TIA for any input.

 

[jimmbo]

That Engine's charging System is Unregulated, and as Rpms increase so will the Voltage. The Battery is the Regulator, and while the Voltage is a but high, the Current is not that great(If I recall, the Charging System was rated at 6 Amps).
However, what exactly is the the Rpm you get when it is running at WOT? 5500 is the upper Limit that that Engine is specced to run at. If you are exceeding that, then you need a higher Pitch Prop, that could explain the 17 Volts. Also it is Imperative that you only Use a Wet Flooded Cell Battery that is not a Maintenance Free design, as you do need to check the Electrolyte Level on Occasion, topping it as needed

 

[phx5kegsman]

I believe mine is 9 or 10 amps(power trim n tilt).
I don't run my motor at WOT because I stull have throttle left at 5600rpm. How could the prop be causing the high voltage? I believe I am running a stock 19P 3 blade aluminum prop. Any suggestions? And I use a flooded cell starting battery. Thanks

 

[jimmbo]

Yes the Models with Power Trim from the Factory did have a 10 Amp Alt. I would verify that the Dash Voltmeter is Accurate, and same goes for the Tachometer, as you would need to have a very Light and Small Boat to get that engine over 5500 with a 19 in prop, unless you have a lot of Slippage.

How old is the battery, and when was the last time you checked the Electrolyte Level?

 

[phx5kegsman]

The sticker on the battery is 6/22. I checked the water with one of those "turkey baster" style tester last year and all were good. What do yo mean by "slippage"?

 

[Crosbyman]

unless you have indications the battery is being overcharged or " light bulbs burning out) I would not worry about it it can handle itself and has indicated it will regulated the incoming charging current.

what is more problematic is accessories like fish finders which can initiate a shut-down due to voltage being to high.

I had this problem years ago with a Merc Classic 50 .

Solved the problem by adding a voltage regulator circuit to give me a flat 12volts. there are several such unit on Amazon today. In my application I used 3 small Radio Shack 3 pin units and bridged them for a greater amp supply to my fish Humminbird finder .

never had shut downs after.


as a suggestion .... or locate something similar for a best physical fit under the cowl or go OEM/CDI

https://www.amazon.com/Regulator-Rectifier-Evinrude-Outboard-1980-2001/dp/B08V11FT4C/?_encoding=UTF8&pd_rd_w=qHDnU&content-id=amzn1.sym.c92d66bb-843a-4d93-9389-f839616d5d53%3Aamzn1.symc.f3a6ae52-fb92-4bbd-ba18-628777ebc1c0&pf_rd_p=c92d66bb-843a-4d93-9389-f839616d5d53&pf_rd_r=DYWK6DGWEKQ0YEW34WMW&pd_rd_wg=kFN6B&pd_rd_r=5f27089f-78e3-4d0d-82d7-fe048a63fa4f&ref_=pd_hp_d_atf_ci_mcx_mr_ca_hp_atf_d

 

[saltchuckmatt]

Slippage... Spun hub, slipping.

Rpm's are to high. Wrong prop or failed hub are some of the things that caused that.

Try boat loaded up....(Humans, food, beer, fishing equipment, hot woman with not much clothing on.....throttle to the floor, trimmed up.

With this example you should not go over the suggested RPMs unless the "hot woman" needs it!

 

[phx5kegsman]

Crosbyman: is the regulator rectifier shown above different than the stock rectifier? It looks the same.

Saltchuckmatt: I have a spare prop that I will put on. It's the same 3 blade 19P, but at least I'll be able to rule out/ confirm slippage. I'm going to the lake tomorrow. Thanks for the help

 

[Crosbyman]

the same no... physically yes

the description fits so the reg. shouuld fit.
80 commens at 4.5 seems good. few bad ones but they could have been bad installations. most users seemed happy

it is a suggestion ..up to you or if worried go OEM.

 

[Faztbullet]

That part posted is just a standard rectifier and unregulated, OP will still have same problem. Below is the one OP needs..

Amazon.com

 

[Crosbyman]

very odd it does say rect & reg ... although it has no extra 4th black wire is it not possible its metallinc body gets a ground referrence by simply bolting it up ??

if it was not a rect-reg one would expect a lot of adverse comments 4.5 on 80 reveiews isn'T bad although some have complained but not a majority it seems