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1978 Evinrude 85 hp Electrical Issue

C

citori63

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"Put a brand-new battery in th

"Put a brand-new battery in the other day, started the engine fine, ran the boat approx. 1 hour and shut it off to fish. After fishing for about an hour, went to start it, and the starter barely turned over. Finally started, but I was wondering why a fresh battery would do that. I had not used any accessories while fishing.
Then I ran the engine for at least 2 hours without stopping, and when I shut it off, it refused to restart. Checked all my grounds, and they seemed fine. Possibly related: Lately the tach has been pegging to max every time I turn the ignition key on, and stays at max when engine is running (even at idle.) When the engine refused to start the other day, I noticed the tach was going up to about 3000 when I turned the key on, and as the battery got progressivley lower, the tach reading kept dropping (this is with the engine NOT even running.) I'm thinking of replacing the rectifier...am I on the right track? Thanks."
 
"It sounds like maybe a rectif

"It sounds like maybe a rectifier, but might want to check system first. Do you have a manual?"
 
"Did you by any chance acciden

"Did you by any chance accidently install that battery backwards...... or if installed properly, the battery was charged backwards?

The tachometer is pegging backwards of what it should. The battery is discharging instead of charging.

Check the polarity of that battery."
 
"Thanks for the excellent repl

"Thanks for the excellent replies.

It is possible I installed the battery one time with polarity backwards; I can't say with any certainty whether or not I charged it backwards.

I do know the tach has been pegging at idle with several different batteries.

By the way, the engine ran fine every time. But this last time, when it refused to start, we tried jumping the battery with another boat, and all we could get was one turn of the starter, and then nothing."
 
most often its bad commection

most often its bad commection or battery cables that are corroded preventing the flow of electricity from pos to neg.or the starter is drawing to much ampereage.it may be shorted
from commutator.battery needs to be load tested
to prove its integrity.check all grounds for continuity.
 
"I just re-checked: The power

"I just re-checked: The power and ground cables coming from the engine were definitely hooked up correctly to the battery. But even when correctly hooked up, the tach is till pegging to 7000 as soon as I turn the key on. (The tach has worked properly in the past.)

I checked every ground, and they are all tight and clean. Could a bad rectifier cause the tach to peg without the engine running?"
 
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