Motor help - PLEASE!

[jp]

Well, I should be fishing today, but the boat isn’t cooperating.

I have an older Johnson 150 - 1980. Very dependable until the last month or so. I’ve put the battery on charge for a day and went to start and it’s sluggish. Now, this Johnson is cold natured, but once it starts, it’s good as gold.

I’m trying to start the motor and it does take some cranks. After about 2/3 minutes with a full charged battery, it doesn't seem to have enough to continue a good starting surge. I charged the battery over night. It doesn’t seem to have enough to get it going. I checked the battery and it read 12.60 which seems like this has enough. So I used a jumper cable from my car and the power was there. Shouldn’t 12.6 be enough to start the boat even if it’s cold natured? Once I put the car on it, I could hear the extra power. Does the car provide that much extra amps? Is there something on the boat going out that prevents the battery amps to be minimized? Why wouldn’t the normal battery just start the boat?

Very frustrated.
Any help is appreciated.

[stratos185]

From what you are saying by adding a jumper battery and all is OK, I think that your starting battery may have a weak cell. Take it to your local auto parts store (Advanced Auto or Auto Zone, etc) and have them put a load on the battery to check the strength of the cells. I believe you will find that you have a weak cell and a new battery is the only cure.

[Embrey]

or clean your posts and cables

[R19]

At 12.6 V your battery is weak. I dont know why 12 V is not enough but for some strange reason a fully charged 12v battery will read 13.2-13.4V. I know there is not a lot of differance between 12.6 and 13.2 but it is enough to make the battery weak enough to not start. As mentioned before take the battery to a auto parts store and get a load test.

[R19]

I remember going over DC voltage last semester in class at school. I went and looked in my text book and 12.67 V at 68 dergees F is considered charged. If the dempature drops to 20 degrees F 12.0 V is considered dead. At 68 degrees F a fully charged battery will normally read 13.6 V + or - .2 which = 13.4-13.8V. Just 1 drop in volts can drastically reduce the performance of a 12v battery.


When you add the car battery by jumper cables your are making a parallel connection. Your are not increasing the cranking voltage you are just increasing the reserve capacity buy adding another battery. The extra power you saw was because the car battery was stronger than the boat battery. When cranking the motor you did not increase the volts to 24. The stronger car battery carried the load.

[coombro]

I remember going over DC voltage last semester in class at school. I went and looked in my text book and 12.67 V at 68 dergees F is considered charged. If the dempature drops to 20 degrees F 12.0 V is considered dead. At 68 degrees F a fully charged battery will normally read 13.6 V + or - .2 which = 13.4-13.8V. Just 1 drop in volts can drastically reduce the performance of a 12v battery.

Ah yet you need to figure in the 10% voltage rule. Voltage fluctuation is figured at the 10% rule for operation being ac or dc. 12 volts is 12 volts. His sounds like an amp problem. You can have 12 or 13 volts all day yet if you don't have the amperage to back it up your dead in the water.

[Embrey]

Ah yet you need to figure in the 10% voltage rule. Voltage fluctuation is figured at the 10% rule for operation being ac or dc. 12 volts is 12 volts. His sounds like an amp problem. You can have 12 or 13 volts all day yet if you don't have the amperage to back it up your dead in the water.

yup...mine has read anywhere from 12.3-12.7 for years and still cranks like a champion

[basshuntin]

You can not tell if a battery is bad by reading the voltage when the battery is not under a load. If you can, check the voltage while the motor is cranking. My bet is your battery is bad and your voltage is dropping way down when you put it under a load.

[mkspw]

get someone test it for a bad cell.

[coombro]

You can not tell if a battery is bad by reading the voltage when the battery is not under a load. If you can, check the voltage while the motor is cranking. My bet is your battery is bad and your voltage is dropping way down when you put it under a load.

Agree 100% like some one said take it to Auto Zone they have a special tester there that will pull it down while testing. . Like that someone said a dead cell will still read 12 volts and run some items, but when it takes a load such as turning over a motor it can't hang.

[floatman]

I have a 200 Merc, the starter was going bad, it acted like a dead battery, if the battery is food might be the starter.

Gary

[floatman]

not food, GOOD........LOL