high voltage at high rpms??

[cacklerslayer]

I know i have already posted this problem on here before but i forgot wait kit to get. I have a 1978 25hp evinrude electric start. When im at an idle or just trolling my volts will stay between 12.5-13.5, but when i try to get up and run bringing the rpms up my voltage will jump clear up to 16 or so and make my depth finder go nuts and shut off. I think i needed to get a voltage regulator kit to solve but cant remember what one. Also will this problem damage things on the motor like the brainbox?

 

[emdsapmgr]

Re: high voltage at high rpms??

Your voltages you are seeing are normal for a charging system which is unregulated. Once the battery charges up, the voltages will increase to 16 or slightly more. This is also normal for lower hp engines and early V4's and V6's. The high charging voltages are separate from the ignition side of the stator, so will have no effect on the power pack, timing sensor or coils. I looked at a 1992 25 and it uses the same type unregulated rectifier as your 78. You may be able to run your fishfinder off your trolling battery, but it may not like the electrical interference from the trolling motor...

 

[cacklerslayer]

Re: high voltage at high rpms??

Your voltages you are seeing are normal for a charging system which is unregulated. Once the battery charges up, the voltages will increase to 16 or slightly more. This is also normal for lower hp engines and early V4's and V6's. The high charging voltages are separate from the ignition side of the stator, so will have no effect on the power pack, timing sensor or coils. I looked at a 1992 25 and it uses the same type unregulated rectifier as your 78. You may be able to run your fishfinder off your trolling battery, but it may not like the electrical interference from the trolling motor...

Ok so if i run an inline type regulator on my fishfinder then ill be good to go.

 

[boobie]

Re: high voltage at high rpms??

BRP has a voltage regulator kit, part # 173640 which you may want to look into.

 

[jtexas]

Re: high voltage at high rpms??

Ok so if i run an inline type regulator on my fishfinder then ill be good to go.

I've never tried this myself (my FF tolerates up to 18 or 20V), but wouldn't hesitate if I needed to. Couple things to look out for if you go with a cheap regulator (like from radio shack, for example):
1. Upper current limit of the regulator -- most FF draw way less than 1 amp -- GPS/sonar combo's usually a bit higher. Add a heat sink if necessary.
2. Lower voltage limit of the FF -- cheap regulators often drop a couple volts, so when the motor's off, input voltage will be ~ 10.7 with a fully charged battery, but should always be above 10.

In the mean time, turning on the lights or some other accessory while running full throttle, might bring the voltage down within tolerance of your FF.

 

[dew2]

Re: high voltage at high rpms??

Have you tried to ground the battery to the boat? Neg.batt post to boat,That may stop any interference to the sonar.

 

[cacklerslayer]

Re: high voltage at high rpms??

Have you tried to ground the battery to the boat? Neg.batt post to boat,That may stop any interference to the sonar.

I havent tried that. Im not sure what i would ground to, my boat is fiberglass?

 

[cacklerslayer]

Re: high voltage at high rpms??

I've never tried this myself (my FF tolerates up to 18 or 20V), but wouldn't hesitate if I needed to. Couple things to look out for if you go with a cheap regulator (like from radio shack, for example):
1. Upper current limit of the regulator -- most FF draw way less than 1 amp -- GPS/sonar combo's usually a bit higher. Add a heat sink if necessary.
2. Lower voltage limit of the FF -- cheap regulators often drop a couple volts, so when the motor's off, input voltage will be ~ 10.7 with a fully charged battery, but should always be above 10.

In the mean time, turning on the lights or some other accessory while running full throttle, might bring the voltage down within tolerance of your FF.

I will look into these 2 aspects for sure thanks! I would try and run with my lights on but i do not have my lights wired back in yet. They went bad, so i have to use portable lights for know