9.9 charging voltage and Battery.

driver0606

Seaman
Joined
Sep 9, 2015
Messages
56
I hope everybody had a good Christmas.
I have a 1988/9 Evinrude 9.9 electric start recently fitted with a new rectifier, fitted to a 9ft. speedboat. When running fast it used to show about 14v - 15v on the voltmeter. It has now started showing about 16v. It has been suggested that there may be a bad cell in the 3 year old battery, although it starts the engine well enough. My questions are-
1) If I continue to use it as is, will running with this high voltage damage the electrics in the engine?
2) The battery is 24 amp hour, if I change it, would a smaller battery, say to about 12 amp hour to save weight, is that big enough for the motor?
Many thanks for any advice.
John.
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
16V is not uncommon with a fully charged battery. There are a jillion rigs running around out there with no problems, but some electronic accessories may not like it.

Yes, your battery choice probably is causing most of the situation.
 

hemi rt

Petty Officer 1st Class
Joined
Jul 1, 2010
Messages
321
While running you should be charging at over 14 volts but under 16 volts, charging over 16 volt; it means either your rectifier/ regulator is bad or you have a bad battery. Usually it is a bad battery.
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
36,031
There was no voltage regulator offered as an option / or needed for that motor.----Just used a rectifier.
 

driver0606

Seaman
Joined
Sep 9, 2015
Messages
56
Thanks Guys. That puts my mind at rest regarding damaging the motor's electrics. No problem with the boat's electrics, GPS speedo 9v - 32v. Any comments regarding battery capacity, please?

Happy New Year!

John.
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
7,985
16 volts is ok for that system. It is an unregulated system and uses the battery as the regulator. That is why you need to use batteries that can be refilled instead of maintenance free batteries . If you want to correct that get a regulator rectifier combo if on is available for it.
 
Last edited:

oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,598
Service manual minimum battery requirements are 350 cold cranking amps (cca), and 100 minute reserve.

Sounds offhand like you might need to top off your battery with distilled water, and give it a full shore charge — probably wouldn’t hurt to take it into a car parts store, and have it tested for capacity and load. With a fully charged battery, you should expect to see around 14 volts on your volt meter. (Rectifier for your motor, btw, is the four lead model — one red and three yellow.)
 

driver0606

Seaman
Joined
Sep 9, 2015
Messages
56
Many thanks, everybody. I can see where to go now, starting with checking and charging the existing battery.
 

Vic.S

Rear Admiral
Joined
May 4, 2004
Messages
4,690
Many thanks, everybody. I can see where to go now, starting with checking and charging the existing battery.

Charge the battery with a good automatic charger ( A 4 amp one will be more than big enough for a 24Ah battery ) until the charger goes into float or maintenance mode.

Let it stand with no further charging or load for 12 hours then measure the volts with a digital voltmeter. If the battery is good it should read 12.7 ish to 12.8 ish

Allow the battery to stand with no further charging or load for several days, preferably several weeks. The volts will slowly fall but it should take several weeks to fall below 12 .5.

If all seems good based on the above as a final test get it load and capacity tested by a battery supplier or auto parts store.


If you want to save on space and weight you may be able to find a compact AGM stater battery. but I dont know what brands you will have in Canada ( Red Flash by DMS Technologies in the UK)

BUT if you run any other electrical equipment on your boat be sure that the battery has a large enough Ah capacity to ensure that you never run below 50% state of charge before recharging.
 
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