1988 Evinrude 70 HP power loss / dead batt

[richardbrown67@yahoo.com]

On my 1988 70 hp Johnson outboard, I can charge the battery and start the engine, and all is fine.... Good idle, smooth acceleration. Then, after running smoothly for a short while, maybe 5 to 10 minutes, like a switch, the engine cuts to minimal power. Each time this has happened, I have immediately headed back towards the dock, limping along for about 5-10 minutes. Fortunately, I have made it back to the dock, barely. When I slow down to moor the boat, the engine dies. Then there is no battery power to re-start the engine. The battery is new. The battery will hold a charge on its own. The battery only dies if I run the engine as described above.

This reminds me of running a car with a failing alternator - limping along until the battery gives out completely. But the intermittence is puzzling to me. Why will it run really well for a while and then just cut out?

One final thing - just before this problem started I changed the lower unit gear oil using Penzoil 80W-90. The gear oil change was highly overdue. I don't see how this could cause any of the issues about the power, particularly the battery going dead, but, I figured I would mention it.

Suggestions?

Thanks

richardbrown67

 

[mrcj001]

Re: 1988 Evinrude 70 HP power loss / dead batt

The battery may be new and hold a charge but you may want to do a load test on it. Batteries may seem good until you put a load on them.

I would test the rectifier on the engine. The OMC Service Manual instructs on how to do it. The problem sounds like a ignition problem.

Did you install the gear lube from the bottom or the top?

It need to be installed from the bottom......

 

[DJ]

Re: 1988 Evinrude 70 HP power loss / dead batt

1. A simple volt meter will tell you if the engine is charging the battery. Just place the leads across the battery terminals while the engine is running. You should see 13+ volts.

2. If not, more than likely, your rectifier is shot. They are relatively cheap. Look here on iboats for one.

3. OMC's are notorious for corroded negative battery cable engine block grounds. That is due to the relatively high charging voltages they create. REMOVE and clean the negative (ENGINE BLOCK) battery ground and clean it thoroughly.