Do I have the right battery for a 75hp efi merc 4 stroke???

[bfensom]

Hey, Just want to say I am new to the boating world and the forum so please take it easy on me haha...

I just bought an 07 Legend Xterminator with a 75 merc 4 stroke on it and the main problem the guy had was the battery wouldn't hold a charge. He bought it new in June, but for some reason won't hold a charge. Its a Motomaster Nautilus 80a starting battery.

So what I am wondering is could it possibly be the battery is faulty or maybe is it just not the right battery for the motor?

He said the trolling motor battery was dead as well so I just bought a 70a starting/deep cycle for it which I hope was the right size lol. The trolling motor is a motorguide 55lb wireless which I believe is standard with this model of boat... Any help would be great thanks!!!

 

[undone]

Take the battery to an auto parts store and they will check it for free.

You didn't get the correct battery for the trolling motor, you need a deep cycle battery, not a dual purpose one.

Use the new trolling motor battery for the main motor and buy a deep cycle for the trolling motor.

Also check to see if the charging system on the main motor is working correctly, the battery may be good,

 

[bfensom]

ok thanks! So the new battery will have enough cranking power for the size of motor? its 625 marine cranking amps, 70 amp hours, 120 minute reserve capacity

 

[Texasmark]

Deep cycle batteries will start engines. I had one on a John Deere 70 hp diesel tractor that I bought with it in it, which had been in there for half a dozen years. I used it for another couple before I replaced it. I guarantee you a 70 hp diesel tractor in the winter is like trying to start 3 or so 2 stroker OBs.

Suppliers advertise combination batteries that are supposed to have enough current to start an engine and also tolerate high discharge cycles. As I said, this DC battery would start this JD tractor and did for years and I guarantee you that required more current than any outboard out there x 2 or 3.

Not familiar with what you bought. Any quality size 24 battery will start that engine. I have started a 70 hp Chrysler years ago with a crank rope so it doesn't take a lot of whoopee.

Don't know where you got your info but to me you went to the wrong place.

Mark

 

[bfensom]

Ok so should I keep that 625 mca 70a starting/ deep cycle for the motor?

 

[roscoe]

yes

 

[bfensom]

Awesome thanks guys!