85HP Johnson 1971 - Weak spark

[Davek55]

Hi There,
I am new here and have already learned a lot by browsing the forum.

My 1971 85HP has very weak spark. I have difficulty starting. Once it is running it runs great. I tried Joe Reeves method of checking spark with a 1x4 with nails bent to create a 1/4" gap. The spark will not jump the gap. He suggests that it should jump 7/16" with a snap... With a sparkplug I have a dim but obvious spark at all four cylinders.

Could it be the points gap? What should the gap be?
A faulty stator? Low voltage somewhere on the primary side? I have experience with automotive ignition systems, but I don't even know what a stator is! Any guidance greatly appreciated!

 

[R.Johnson]

Re: 85HP Johnson 1971 - Weak spark

That is a battery CD system. Where you do have spark, but weak. I would fist clean the points, and set them at .010

 

[Davek55]

Re: 85HP Johnson 1971 - Weak spark

OK I have cleaned and increased the points gaps one notch = .010"
I have checked the voltage at the engine terminals and have 12 volts.
Maybe the spark is normal... still looks weak to me.
I started the engine in the driveway with garden hose on. It started OK. I think starting is more difficult in the lake.
The electric choke fully closes butterfly. I have fuel for sure. Maybe I needed to choke longer at the lake.
The starter seems to kick out the instant the engine fires. Maybe I need to get the starter adjusted so that it remains engaged longer.
This boat used to start so easy every time...I wonder what has changed... I will go to the lake tomorrow and see how it does.

Any suggestions of what may cause hard starting?