15 volts charging from a 1979 70 HP Johnson. Abnormal?

[marcusknight]

I have this engine and when I first start it, it puts out about 13 volts but it gradually creeps its way up to 15 or more volts after a few minutes. Is this abnormal? I am using the same 24 series deep cycle battery I have been using since 2007 and I recently noticed some faint hissing from the battery when I turn the engine off. That prompted me to check the voltage for the first time.

Some people say that it is normal for voltage to be this high on older engines. Is that correct? Should I be using a different battery, perhaps one that is not maintenance free where you can add water? What are these called and where do you find them? I only ever see maintenance free deep cycle batteries at retail places.

 

[emdsapmgr]

These early engines use a rectifier in the charging system, instead of the later combination rectifier/regulator. So, your charging voltage is unregulated: what you are seeing is normal. Since the engine's charging rate goes this high, it tends to "cook" the battery somewhat- the longer you run it. So, I'd check the water level in the battery more frequently to be sure you keep the plates covered with water. A marine "starting" type battery (not a deep cycle) is best for your application, though some (expensive) high-end deep cycles are advertised as being able to perform well in starting type applications.

 

[Barnacle_Bill]

I would have the battery load tested. 7 years is pretty old for a marine battery.

 

[marcusknight]

can someone give me a link to a battery that they would recommend for this higher voltage?

 

[boobie]

Try Interstate Batteries.com.