1974 Evinrude 25Hp Electrical questions

[FormerParatrooper]

I am looking at the service manual for an 1974 Evinrude 25Hp Model 25452M. The manual states that the "Starter amperage draw when cranking " is 120 amperes. This is a 12v system.

I am not an electrician, so my questions:

There is a 6 ga battery cable installed, and it does not reach where the battery is on my boat. I would need to extend it to a total length of 14 feet to reach the battery and have about 10% slack in the line. Would I change the wire to 4 ga for the length of the run?

What size fuse would I use?

 

[Weldorthemagnificent]

I'm no electrical engineer but I used a set of booster cables for wire in my boat. Trolling motor and batt up front, booster cable wire to a junction block where it ties into the motor, bilge pump, fish finder etc...


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[timsmcm]

What size booster cables? They come in many sizes of wiring.

 

[Weldorthemagnificent]

I'd have to go look to be honest but they aren't 4 ga. Lol. I figured that if they we're engineered to start a car, it would probably run the starter on a 20 hp boat motor. Early spring, booster cables be on sale. I got a good quality pair for half price last April. I went through the same thing man. I looked at heavy wire, welding cable even. Then for a budget boat I came up with the booster cable idea. Worked mint all last year. They never got hot. Motor cranks for what 4-5 seconds? Maybe 3 times when cold and just a bump when it's warmed up.


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[nccatfisher]

I am looking at the service manual for an 1974 Evinrude 25Hp Model 25452M. The manual states that the "Starter amperage draw when cranking " is 120 amperes. This is a 12v system.

I am not an electrician, so my questions:

There is a 6 ga battery cable installed, and it does not reach where the battery is on my boat. I would need to extend it to a total length of 14 feet to reach the battery and have about 10% slack in the line. Would I change the wire to 4 ga for the length of the run?

What size fuse would I use?

I would drop it down to 4 and forget the fuse unless you are looking for a place to cause problems. Just make sure any place it goes through seats etc that you have gromments etc so you don't have chafing issues.

 

[timsmcm]

That is a long run for a starter? 6 would work 4 even better.

 

[FormerParatrooper]

The run is long because I have the battery in the front of the boat. It is a 14 ft boat and after making the turns from motor to floor and running up to the front it is almost 14 ft.

Thanks for the ideas.

 

[Pappy]

Battery cable run encompasses the total length of the run, not just one way. You actually have a 28 foot run.
The good news is that the load is not 120A the entire time the starter runs. Once it has the flywheel up to speed the amperage drops significantly.
Do not listen to guesses. Here is a chart. You are probably looking at 4 ga. At that price I would find something else to put in the bow......

 

[FormerParatrooper]

Battery cable run encompasses the total length of the run, not just one way. You actually have a 28 foot run.
The good news is that the load is not 120A the entire time the starter runs. Once it has the flywheel up to speed the amperage drops significantly.
Do not listen to guesses. Here is a chart. You are probably looking at 4 ga. At that price I would find something else to put in the bow......

Thanks Pappy. I believe I will bring the battery to center of the boat since the current cables will reach and redo my low volt lighting run.

Do you suggest a fuse at the battery?