Johnson 115 Charging System

Electrical and electronic topics for small boats
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Joined: Fri Oct 16, 2015 3:45 pm

Johnson 115 Charging System

Postby PeteB88 » Sat Jul 16, 2016 1:28 am

Looks like the charging system [of my Johnson 115-HP outboard engine] is not working. I have had no time to use my Outrage 17 but plan to get to it the rest of the summer. I keep batteries charged, take a spare with me for short cruises, and have had no failure other than after several hours of operation my Raymarine combo kicks off with a low voltage condition, which is my indication of time to switch batteries or go home.

What is troubleshooting procedure? I understand pulling flywheel is necessary and have no hesitation to dive in.

I posted same concern last year.


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Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula

Re: Johnson 115 Charging System

Postby jimh » Sat Jul 16, 2016 6:27 am

What is the Johnson 115-HP outboard engine model number?

The typical alternator on an OMC V4 consists of:

--magnets embedded into pockets in the flywheel assembly

--coils in a stator assembly

--rectifiers and possibly a voltage regulator in a Rectifier-Regulator assembly

--several cables and connectors that connect the electrical components

The simplest test for charging current to the battery from the alternator is to look for an increase in the terminal voltage of the battery when the engine is running at high idle speed.

The component most likely to fail is the Rectifier-Regulator assembly. Typically this assembly is an un-repairable part. Aftermarket replacement parts are available from CDI. A typical Rectifier-Regulator assembly for a Johnson 115-HP engine c.1990 would be: ... 95-878331/

Typically the Rectifier-Regulator assembly bolts onto the engine block and receives cooling water. A gasket is also necessary to maintain the water jacket seal.

The factory service manual gives guidance on how to troubleshoot and diagnose problems with the battery charging output from the engine. If you plan to perform your own repair and service to the outboard engine, having the factory manual is a very good investment.

It is unlikely you would have to pull the flywheel, unless the flywheel must be removed to access the Rectifier-Regulator assembly for replacement. If you do remove the flywheel, it is usually necessary (or at least recommended) to re-check ignition spark timing and to reset the TOP-DEAD-CENTER indicator mark.

Since your time available to use the boat so limited, you ought to consider having the charging system repaired at a competent dealer. This will save your time, and allow you to use your limited time to actually go boating instead of making repairs.