1977 Johnson 115 recharge a deep cycle?

[takirb]

I recently purchased a used fish and ski, with a rebuilt 1977 115hp Johnson. The battery I was left with is an old Interstate deep cycle/RV with 550 mca that wasn't charged enough to turn the motor when I purchased the boat. After a full charge, it sat on my tackle box for 3 hours unplugged and dropped down to 3/4 charge. I believe its bad. I have an Everstart Marine deep cycle battery that holds a full charge fine, rated at 720 mca, and tested good at 670 cca today. Since the mca rating is higher, I figured id save some $ for right now and use the everstart as a starting battery and to run stereo (stock radio, old tape player model and 5" speakers) while im on the water. Will the 77 johnson recharge this Everstart sufficiently under normal motoring? I have 2 seperate batteries for the trolling motor that charge just fine, so thats not a concern.

 

[Silvertip]

Re: 1977 Johnson 115 recharge a deep cycle?

The capacity of a battery has nothing to do with whether the charging system can actually charge that battery. What does matter is the amount of TIME it takes to charge it. An engine with a 15 amp alternator for example puts 15amps back into the battery each hour it runs at WOT. If you consumed 30 amps from the battery over any period of time, it would take two hours of wide open running to replace that power. The 15 amps by the way is total output so you need to subtract the current draw of accessories that are running while the engine is running. The long and short of this is that you can have two or three batteries in parallel and the engine will provide a charge to them. It is simply a matter of how long it takes to fully top them off.

 

[reefrunner7]

Re: 1977 Johnson 115 recharge a deep cycle?

I've learned so much from these great guys on here! I learned the hard way this past season even with 2 battery's on board I installed a meter so I can monitor each battery in relation to it's charge. Also every other time I take her out fishing I pull one of the battery's out and take home and trickle charge it because the motor just doesn't do the full job. Or if you take your boat home with you hook a charger up to the batt to keep them fully charged they will last longer.

 

[takirb]

Re: 1977 Johnson 115 recharge a deep cycle?

I ended up having to compromise. I took the Interstate battery to AutoZone and it tested fine, they told me it was only 78% charge just 'cause it was cold (although deep cycle battery held 100% charge just fine?). So i tried to install them both but i don't have the room in the back due to the boat's wiring getting in the way. So i left the Interstate battery on the trickle charger overnight in garage, wired up the deep cycle to the boat and plugged in the onboard charger overnight, then placed the Interstate onboard that day as a backup but had 0 problems at all yesterday (never even needed it). We only ran the stereo while the motor was running, but fish finder stayed on all day. Granted, we ran almost wide open throttle for 20 min spurts going from spot to spot, and when i got the boat home the deep cycle still showed 100% charge Although the MCA rating is higher on the deep cycle, it didn't have as strong of a start as the group 24 but had plenty to do the job. Prolly due to the thickness of the plates i guess regardless of MCA rating...