1970 Johnson 85 hp CDI questions - first ever boat

Hi, I just joined the forum so I could ask a question regarding my first ever boat and outboard.

I took a 1967 17' V-hull fish-and-ski with a 1970 Johnson 85 hp V4 (85ESL70D) on a trade for a gun that was only worth about $300, if that. I figured that the fairly new and sturdy trailer was worth more than $300, and I knew that the Johnson was worth a few hundred in parts if nothing else.

Being close to Lake Guntersville and the Tennessee River, I was sorta hoping that I would be able to get everything up and working on the cheap and have some fun fishing, as I do enjoy fishing. At the same time, I new if it was going to require too much time and money that I could just sell it and make a profit.

Anyway, now that I've cracked into the boat and motor I am fairly optimistic that I can get the boat and motor up to snuff without too much time and money. The floor was starting to rot, so I ripped it out fearing the worst, but the stringers were unscathed and the transom is solid as a rock.

The motor has great compression (all 4 cylinders within 5 psi of 115 psi), cranks over super fast with my brand new battery, and is almost uncannily clean. When you take the cover off you would swear the thing was just manufactured.

The only issue is...wait for it...the infamous ignition that I've been reading about on this and other forums for the past few days. The motor clearly already has a recently replaced CDI box, but it's bad again (power to the correct terminals when ignition is on, but it fails the lightbulb test).

So, I could buy the CDI box with coil for $230 plus shipping and call it a small price to pay for fun on the lake, but I know this will happen again and again (just google 1970 Johnson 85 hp no spark).

My question is: Has anyone found a way to get these early (1968 to 1972) 85 hp Johnsons to run reliably for more than one season per CDI? I really don't want to/can't afford a new CDI every season. I know about the MSD ignition mod, but I haven't found too many people who actually end up successfully getting that to work long term, and it doesn't really save you any money any more because the cost of the MSD has gone up over these last few years. I've also read one thread about using a 12 volt diode, but my electrical engineer friend says that sounds like hocus pocus (correct me if I'm wrong) and an improper use of a diode.

Also, I know some people have tried switching to condensor type ignition systems, but that doesn't last long and tends to destroy the distributer points as I understand it.

Here are my thoughts on the matter. These motors obviously ran for many years without problems when they were new. Only now that they are getting old do they chew through the CDIs. There must be something else that goes bad on these motors that causes this behavior. One thing I did notice is that with my ignition in the run position, I only have 11.8 volts to the amp, but 12.6 at the battery. During cranking, the volts at the amp drop to 9.7.

Could it be that the wiring harnesses have gotten old and need to be replaced/rebuilt? All the wiring is there and has continuity, but that level of voltage drop clearly indicates an issue.

Anyway, what's the current news on these motors' ignition systems?? Is it worth it to spend money on this motor? Any ideas?

Thank you and I would very much appreciate a response, and I will try to answer all questions thoroughly.

Re: 1970 Johnson 85 hp CDI questions - first ever boat

Wait, CDI? Doesn't this motor have a Distributor? Are you calling the Amplifier a CDI?

Re: 1970 Johnson 85 hp CDI questions - first ever boat

It IS a CD ignition system. Battery CD, as opposed to Mag CD found on newer motors. And yes it is an amplifier.

I think you need to address the low cranking voltage first. There may be nothing wrong with the amplifier. You are correct, there is no excuse for blowing amps every year. Most of that is caused by ignorance and carelessness, as well as self-invented "tests".

If there is a weak point it is the distributor cap & rotor. There always has been a lot of spark loss going through it. But they SHOULD be runable. Another problem is the idea that "It always is the black box" mentality.

Get the voltage problem fixed, service & clean the distributor & points & reverse cut-out ring. Then see if you have spark off the coil's spark wire before going through the distributor.

Forget the stupid light bulb test. Disconnect and unbolt the coil, then unscrew the wire from the distributor cap. Then remount and connect the coil. Rig up a spark gap off the end of the spark wire. Now see if you have a healthy spark. If you do, there is nothing wrong with the amp or coil. If no spark, disconnect the wire between the amp and timer base, and with key turned on, brush the wire lightly across an unpainted, grounded part. There should be sparks across your spark gap. If there is, you have a problem with the points.

Countless peopld have tried converting those things to auto coil & condenser. I have yet to hear of anybody having long term success. Besides, check the price of those points. Are you sure you want to burn up two sets of those every season or sooner?

Re: 1970 Johnson 85 hp CDI questions - first ever boat

Thanks F_R,

I was a little skeptical of that light bulb test myself. I will try to diagnose the low voltage issue, then check for spark after the coil and before the distributor. Hopefully I'll get to it tonight after work, but it might wait until Saturday.

Until then, does anyone have any ideas of where/how to check for low voltage problems? Maybe test resistance across the ignition switch and all other cables from battery to amp?

Thanks!

Re: 1970 Johnson 85 hp CDI questions - first ever boat

I now have excellent spark. The old CDI is just fine. Here's where the problems were:

1) The ignition was sketchy at best. I removed that out of the loop and gained some voltage (I'll have to get another switch).

2) The 20A fuse connectors were corroded. I cleaned those up and gained some more voltage.

3) By far the worst problem was the wire going from the amp to the distributor base. It was practically dust.

4) There was general corrosion on many other connectors (battery, CDI to distributor, ignition, etc.) I cleaned up all connections.

After fixing those, I tested my old, "bad" CDI, and I had great spark! I would highly recommend to anyone who is "burning through CDIs" on these old Johnson 85 outboards to check the condition of wiring and connectors. It may just solve the problem.

The next frontier is fuel. I have no ideas what the carbs are like. I'm going to hook it up and see if it fires and runs.

Thanks for the help.

Re: 1970 Johnson 85 hp CDI questions - first ever boat

Make sure replace all of you old fuel lines with alcohol resistant ones. The ethanol even at 10% will breakdown the old fuel lines.