is too much voltage bad for engine?

I have a 1996 mako 17 with a 1996 Evinrude 112 SPL and know very little about electrical issues. My volt meter is reading low (~10) when boat is off but battery switch is on. When i run engine, volt meter is pinnned high (>15). Battery just recharged and it starts fine. Worst symptom is twice engine power has precipitously dropped when at full throttle and there have been some strange beeps from the console. Have also had some crazy beeps from other electronics (VHF, fishfinder,) Repair guy said he can't look at it for over 2 weeks. I don't worry about damaging the electronics - they have fuses, are old, and i don't use much. I worry about damaging the engine. Is that something to be concerned with? Another post in this forum said the battery can act as a regulator but if its fully charged, it can't absorb the extra output. What about running my battery down a bit until i get this figured out. any help would be appreciated.

Re: is too much voltage bad for engine?

I would suggest you re-post this question in the Electrical, Electronics, Audio and Trolling Motors forum. I doubt you have anything to worry about but I would not want you to take my word on that. Best of luck. Rick.

Re: is too much voltage bad for engine?

flashlight said:

I have a 1996 mako 17 with a 1996 Evinrude 112 SPL and know very little about electrical issues. My volt meter is reading low (~10) when boat is off but battery switch is on. When i run engine, volt meter is pinnned high (>15). Battery just recharged and it starts fine. Worst symptom is twice engine power has precipitously dropped when at full throttle and there have been some strange beeps from the console. Have also had some crazy beeps from other electronics (VHF, fishfinder,) Repair guy said he can't look at it for over 2 weeks. I don't worry about damaging the electronics - they have fuses, are old, and i don't use much. I worry about damaging the engine. Is that something to be concerned with? Another post in this forum said the battery can act as a regulator but if its fully charged, it can't absorb the extra output. What about running my battery down a bit until i get this figured out. any help would be appreciated.

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Yes, excessively high voltage can damage electronics. Battery charge state will not stop this from happening.

Fuses are meant to protect electronics,wiring, etc from too much amperage draw. They do not protect all that stuff from excessive voltage.

Are your volt meter readings from the gauge on the dash, or an actual DVOM (hand held volt meter)? If you are relying on the gauge on the dash, I would confirm the reading with a DVOM. BTW 10 volts from the battery with the engine off sounds like the battery has a bad cell (should be 12.5V minimum). Again, if this is a dash gauge reading, I would confirm it with a DVOM. If the DVOM says 10 volts with the engine off, you need to replace the battery.

If the battery is bad, and you replace it, but the charging voltage still goes high, you need to get your hands on an OEM service manual, and familiarize your self with testing your engines charging system.

Re: is too much voltage bad for engine?

What you have is an unregulated charging system on that mtr and it's normal to see high voltage. What you may do is get a large capacity battery or get a 173640 regulator kit from a BRP dealer. You can also try running with your running lites on

Re: is too much voltage bad for engine?

boobie said:

What you have is an unregulated charging system on that mtr and it's normal to see high voltage. What you may do is get a large capacity battery or get a 173640 regulator kit from a BRP dealer. You can also try running with your running lites on

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Thanks for all the advice. Does any think this could explain the two sudden loss of power experiences I had?

Re: is too much voltage bad for engine?

No, the high battery voltage likely had no effect on your sudden loss of power. Loss of power at high speed can be due to fuel restriction, bad fuel pump or electrical issue. Do you have a lanyard kill switch? Have you cleaned the fuel filters? Antisiphon valve? have you inspected the wiring for bare spots?

Re: is too much voltage bad for engine?

i do have a lanyard kill switch. it fails off easily but oddly, the engine usually keeps running.
have not checked the filters or valve. Working on checking the wiring now. Does a boat like this have a fuel pump or does it just flow in by suction?

Re: is too much voltage bad for engine?

All outboard motors have fuel pumps, except for the ones with built-in fuel tanks on the cowling. These are only small HP motors, however.

Since the lanyard doesn't work, I suspect your wiring has been monkeyed with, or is otherwise suspect.