battery volt to start motor?

[smallboatlover]

seeing i wanna keep the amount of weight low on my boat on stuff like a second battery so i can bring more gas. i was planing on puting one battery back in my boat for my rewiring projcect. but i want to know how many volts does it take to start a 50 hp motor. how far can i run the battery down before the motor wont start any more

 

[JB]

Re: battery volt to start motor?

That is an electrical question, SBL. This belongs in the electrical forum. I will move it for you.

 

[proshadetree]

Re: battery volt to start motor?

I will not get near the water with out a second battery. Personal preference. Actual voltage will vary I have seen 12 volt engines start on 9 volts. Starter resistance an change, wires and cables drop amperage. Exact voltage is hard to pinpoint. If you move to one battery at least include a well charged boost pack with your carry ons

 

[jlinder]

Re: battery volt to start motor?

The question is not one of voltage. Any battery you buy will be a 12 volt battery (12.6 actually). The question is how much current will it provide when you try to start the engine. This is commonly given as a CCA rating (cold cranking amps).

Most any battery will start your engine if everything is working well. The test comes when it doesn't go well.

You crank and no start, so you check your fuel line and try again. No joy. Now check the wiring. Starts to sputter and you think you almost have it. Let's try again, almost there.....

And the starter slows to a slow grind and stops. Bad time to find you have exceeded the battery's limit. The real question is how much reserve capacity will you feel comfortable with?

I don't know how much difference there is in weight, but I guess it is not that much. Is it worth it?

 

[Silvertip]

Re: battery volt to start motor?

The real question is how well does the motor start with a good, fully charged battery? If it does not start easily you best not run the battery down at all. The more it's drawn down, the quicker it will fail to spin the engine. Remember, magneto equipped engines need to spin rather fast to generate the spark required to run. If you are intent on running one battery, it should be the largest capacity you have room for and the budget allows. Otherwise, carry a jump start pack for backup. But make sure it is fully charged before you leave the dock. On the other hand, your engine can probably be rope started. If you don't know how, "learn how" -- Then all of this is moot.

 

[5150abf]

Re: battery volt to start motor?

how much gas do you think you need?

Depending on how far you plan on going you may not nees that much gas, I rarely have more than 4-5 gallons on mine but I don't have to go that far to get on my fishing grounds, maybe 4-5 miles out and back.

If you go with one bat keep a charged jumper packl on board, I have 3 bats on my 16'er, 2 for the boat and one to start.

 

[Limited-Time]

Re: battery volt to start motor?

On a DC motor voltage = RPM and Amperage = turning or spinning force. ex. a 12volt starter motor will turn about half speed if supplied with 6 volts. Its a combination of the voltage (RPM) and the amperage (Spinning Force) the turn the engine fast enough to start.

 

[smallboatlover]

Re: battery volt to start motor?

thanks for all the input. i'm not going to put back two batteries on the boat i would feel safer that way anyways now i know what could happen. and about the gas i like to go as fast as my boat alowes so full throutle is uslley were im at. but im goign to start using the two thirds the way then full but as of right now i used one 6.5 gallon and a 3. but i just boat another 6 gallon to im going to have 15.5 gallons. i was also thinking for longer trips geting another6 gallon. i dont think that i could put a 12g tank in beacuse i dont trailer my boat to past a gas staion to the ramp and the one gas marine dock there is really exspensive.

 

[keninaz]

Re: battery volt to start motor?

Just a note, putting a load on a battery measuring 9 volts may well damage the battery. You should not let them get that low before charging.
Granted a 50 HP motor is not a big block V8 but it's still not good for them.