Cruising RPMs on a 76' 85 Johnson

[ezeke]

Re: Cruising RPMs on a 76' 85 Johnson

If the ignition coils are cracked, discolored, melted, potting deformed or anything else that looks irregular, they should be replaced. The new ignition coils are better anyway. Bad ignition coils can damage the powerpack in addition to giving bad performance and damaging the engine.

You might want to decarb the bottom cylinders again.

 

[iwombat]

Re: Cruising RPMs on a 76' 85 Johnson

I'm right withe ezeke on replacing those coils. If one is cracked and weak the others are probably not far behind. The newer coils are MUCH better.

 

[speedcat2000]

Re: Cruising RPMs on a 76' 85 Johnson

I looked here on iboats, and there are three different replacement units, the CDI Ignition Coil, Sierra Ignition Coil, and Mallory Ignition Coil. Prices are fairly similar. Any preferences or guidance out there?

Ouch, another $120 bucks. Unless i can get away with replacing just the #4. But I know you'll recommend against that.

 

[speedcat2000]

Re: Cruising RPMs on a 76' 85 Johnson

I replaced the coils with Sierra coils. Still won't start without choke, but I take it this is standard with the old Johnsons. When the choke is fully closed, it starts (but it's very hot here in Seattle... perhaps in cooler weather I'll have more trouble starting).

I tested the spark, and got nada, nothing zilch on any cylinders. I figured this was a false negative so I went out on the lake, and it started right up. I ran around for a bit to warm it up, then sprayed the rest of my can (1/3 can?) of Deep Creep into the lower carb unit. It nearly stopped the motor, but never quite did. So this is an improvement! Then after a 10 or 15 minute wait, fired it up and it smoked like hell for a while. Ran it around a while until the smoke was done. I think there might be a little improvement in the shudder at low rpms.

So WTF is with the spark test? I grounded 3 plug wires while testing spark on the 4th, and so on through all the cylinders. The battery is plenty strong. I grounded by sticking a bolt in the boot, setting the other end of the bolt up against the block, sticking it in a cranny or something so it would stay against the motor while turning over. I tried using spare wires to ground them, but could not figure how to get the ground wire to attach decently inside the spark plug wire boot.

It was really sunny today, so I covered up the spark tester with my hand while the wife turned over the motor, I can tell you there was no spark at all. I'd really like to know if I'm missing on a cylinder or not... how to do this if the spark test is coming up false negative? Or what might be going on here?

Thanks

 

[ezeke]

Re: Cruising RPMs on a 76' 85 Johnson

Air temperature has little to do with the need to enrich the fuel/air mix when cold starting, although warmer water temperature helps.

If your motor started, you have spark.

You test for spark with the spark plugs all removed, or with an inductive timing light with the engine running.

Since the engine has to be turning at 300RPM to get spark from the ignition system, removing the plugs gives a no-load condition so that you get the best possible chance to reach that RPM. It is not about grounding the spark plug wires but grounding the spark plugs or the tester is necessary.

 

[speedcat2000]

Re: Cruising RPMs on a 76' 85 Johnson

Thanks ezeke. I looked and did not find such instructions for testing spark. Perhaps a short spark lesson could be added to the "Top Secret File" thread. Just for clueless types like me.