Starting Power - 1973 Johnson 85 HP

[RDJuhl]

Hi,
We can sense the end of winter coming to the Mississippi River in Wisconsin...so it is time to begin thinking about boating.

I purchased an older boat with a 1973 Johnson 85 HP motor last year. The motor has been difficult to start, but once started, runs fine. I reviewed many threads last year, and intend to do a couple things:
1 - replace the ignition switch
2 - rebuild carburetors

I have been concerned that the prior owner did not have a strong enough battery...it is a Autocraft 24 class Marine starting battery (Marine Cranking = 575, Cold Cranking = 460, Reserver = 70). From reading the forums, I know we need a certain # of rpms just to get spark while starting...and that is something that has been inconsistent (based on spark tests). Here are some options...which do you like best and why?
1 - simply replace the batter with a larger battery
2 - buy a new battery and connect in series with my current battery
3 - add a switch which would allow me to draw from my deep cycle battery for starting...basically, would put the deep cycle in series with the starting battery only while attempting to start the motor.

Interested in your thoughts.
Many thanks

 

[Wishiniwuzfishin]

Re: Starting Power - 1973 Johnson 85 HP

I would start by checking all battery connections, battery cables, starter/solenoid wiring and starter/solenoid connections for tightness, corrosion, rust etc.

If that battery is good and fully charged it should crank and start your engine with no problem assuming no ignition problems.

If all the batt. cables and wiring are original, corrosion under the wiring insulation could also be a problem.

 

[Wishiniwuzfishin]

Re: Starting Power - 1973 Johnson 85 HP

Also,you do not want to connect your batteries in series. That would give you 24 volts. You would want to connect them in parallel.....pos to pos/neg to neg....that would keep them at 12 volts but give you more amps (more power)

 

[RDJuhl]

Re: Starting Power - 1973 Johnson 85 HP

Ahh...thanks for the clarification on using the term "parallel".
I have cleaned all connections...but will plan to replace the battery cable when I get started on my boat.