1974 Johnson 85hp

[Rod Holder]

Hi,
Been a while (mostly due to my super reliable 88SPL) since I have been looking for wisdom.

Recent saga. Picked up a project boat with a 74' 85hp Johnson. Fuel was sour and carbs gunked up. Was able to get it to fire for a moment with a quick shot of starting fluid to insure it had spark before I bought it. This engine is fresh water only with 275 hours! It looks like it as well!

Got it home and went thru the carbs and replaced the entire fuel system from the line connector all the way back to a new tank.
Had it running in the driveway in early August. Sat for 3 months while I was unable to get it on the water. Finally got a chance to get out and it would crank, no start. Was probably 35-40 degrees so gave it a quick shot of starting fluid and it started and ran but seemed weak (like running on 2 or 3 cyl). Putted out of the harbor and gunned it. No power at all. Maybe 1,500-2,000 rpm. Popped the cover and found one coil arcing to ground so called it a day.

Got it home and had no spark at all. Replaced the arcing coil, plus another that was cracked and oozing goo. Replaced the rectifier that had a mostly severed red wire that may have shorted. Replaced the power pack.

It would not start. Hooked up a timing light to check for spark. One bank was good, the other not. Switched the trigger leads from 1 to 2 and 3 to 4 and no change. Switched the coil leads and no change. Damn. Pulled and grounded the plugs and all were firing. Put them back in and it started. Warmed it up and it revved up as it should. Odd.

Backed it into the water but left it on the trailer. Would not start. Hit it with some starting fluid and it started but would not rev up as it did earlier that day in the driveway.

Frustrated I called it a day. I do not have a DVA tester so some of the diagnostics are tough. I did get around 3k ohms resistance between the stator leads.

Any and all help much appreciated!!

 

[F_R]

Re: 1974 Johnson 85hp

I think you have a bad stator. That resistance doesn't sound right, but I don't have the specs for that exact model. Is it leaking goo?

 

[Rod Holder]

Re: 1974 Johnson 85hp

The stator looked like new. Almost like it had been replaced at some point. Looked like an updated/improved design (sealed unit, not like some pics I have seen of the original version with exposed pickups).

There was some goo on the block under the stator but definitely not from this stator. The specs I have for stator resistance between the brown and brown/yellow leads ranges from 400-850.

 

[Rod Holder]

Re: 1974 Johnson 85hp

Just thought of another possible related issue. At fast idle, I am only getting around 12.8 volts at the battery. This seemed low as my other engine (1991 88SPL) cranks out at least 14-15 at that speed and upwards of 17 at cruise......

I will double check the stator resistance tomorrow but I am almost positive it was 3k today.....

 

[oldboat1]

Re: 1974 Johnson 85hp

sounds like multiple issues, but thinking carb issues might be primary. It sounds like the carbs really need to be disassembled and cleaned, then reinstalled and synchronized. You said you went through the carbs, so maybe you already disassembled and cleaned them (carb kits?), but intermittant spark or not you should not be seeing improvements from starting fluid unless you have carb problems. If you had stale gas and varnish in there, every tiny opening needs to be cleared. Solvent, soaking, and wire probing. Until the fuel/carb issues are resolved, I don't think you can definitively troubleshoot the electricals.

 

[emdsapmgr]

Re: 1974 Johnson 85hp

Weak ignition components are not unusual on an engine of this age. The components tend to work when the engine is cold, then crap out when it warms to normal operating temps. (usually-but they can fail and not start at all when cold.) It be inclined to verify those ignition compoents first, since you've been thru the fuel system already. Three major components: power pack (just replaced) stator and timer base. The 74 factory manual does not have the latest ignition troubleshooting specs, so I'd go to this website: cdielectronics.com and snoop through their ignition troubleshooting guide for your engine. They list actual cranking voltage outputs for the stator and timer base. You'll need a special DVA voltmeter to read these voltages, but they are more reliable than testing components by ohms. You will find the stator should put out about 150 volts minimum, and the timer base something like either 0.3 or 0.6 volts when you crank the engine. If these both meet minimum voltage output specs, then move on to fuel issues. (One minor issue on these engines-make sure the bottom spark plug wires are not routed close to the two rear lower cowling latches. Weak wires can arc (short out) to them and you won't know it with the upper cowling in place.) Since these engines don't have a computer to interrogate for run hours, how do you know it has 275 hours?

 

[F_R]

Re: 1974 Johnson 85hp

The stator looked like new. Almost like it had been replaced at some point. Looked like an updated/improved design (sealed unit, not like some pics I have seen of the original version with exposed pickups).

There was some goo on the block under the stator but definitely not from this stator. The specs I have for stator resistance between the brown and brown/yellow leads ranges from 400-850.

Yeah, I had it in my mind that it was supposed to be 900 ohms. Of course, that may not apply to an aftermarket unit, which you may have. But still your test result shows way off.

 

[Rod Holder]

Re: 1974 Johnson 85hp

I am 100% certain the carbs are clean. I have been thru this type of carb many times before. Getting a real nice vapor stream from each spark plug hole while cranking. Thinking that I have weak spark and the fact that this engine has a choke flap (not a fuel prime squirt) and that the starting fluid is so much more combustable is the only reason it is starting. I know it has 275 hours as it has the original functioning hour meter.
As I an not going to get a meter with DVA capibility any time soon, I will have to rely on resistance testing to troubleshoot. Will test the stator resistance again, hoping that 3k means that it is toast, causing my under compression firing issue. I will check the one on my 1991 88SPL to see how it compares as well.

Thanks for all your ideas, very much appreciated!!! If anybody has more please jump in!!

 

[Joe Reeves]

Re: 1974 Johnson 85hp

That engine must crank over at least 300 rpm with the electric starter in order to have the spark jump a required 7/16" gap via a spark tester. In order to obtain this cranking speed, the spark test MUST be done with the spark plugs removed. A slow cranking engine will not produce the needed spark.

In cleaning the carburetors.... did you check and manually clean the high speed jets (2 to a carburetor) that are located (threaded) horizontially in the bottom center portion of the float chambers, way in back of the drain plugs? If not, do so with a piece of single strand steel wire.

Fuel must pass freely thru all four of those jets before it can gain access to any other fuel passageway.

 

[emdsapmgr]

Re: 1974 Johnson 85hp

That hourmeter is a good answer! Sounds like a low-hours engine... Again, check out the cdi website, they also have ohms specs.

 

[Rod Holder]

Re: 1974 Johnson 85hp

I have been avoiding the 7/16" spark test, mostly becuase assuming the tester is expensive. I have relied on seeing the plugs spark when removed, an inline cheepo spark tester (it showed spark but was more yellow/orange than blue) and my timing light. Where can I get a legit tester that I can set to 7/16"?

I have a printout of all the tests required, just do not have a DVA type meter. Has anybody ever checked a healthy stator output with a standard meter just to see what it reads? I got 12v DC while cranking (between brown and brown/yellow).

Yes all jets were removed and everything is clean and clear. Plugs are plenty wet with fuel. Cranking speed is A-Ok!!

 

[dazk14]

Re: 1974 Johnson 85hp

I believe you can buy a dva adapter for your multi-meter that is only ~$25

 

[racerone]

Re: 1974 Johnson 85hp

If you have an old piece of plug wire and a piece of plywood you can make a tester of sorts.------You just need to rig up wires with a gap of 7/16" -----And not that expensive to buy either.-----It is the proper way to test the intensity of the spark.

 

[Rod Holder]

Re: 1974 Johnson 85hp

Wow, $25 is not that bad. Will have to look into that.

With that home brew tester, does the plug end need to be grounded or attached to an installed spark plug?

 

[emdsapmgr]

Re: 1974 Johnson 85hp

Here is a pic of the Stevens Instrument spark checker, as an example of a simple tester. About $29 retail.

 

[Joe Reeves]

Re: 1974 Johnson 85hp

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:


..........X1..........X2

.................X..(grd)

..........X3..........X4

 

[Rod Holder]

Re: 1974 Johnson 85hp

I like it!! Thank you.

 

[Rod Holder]

Re: 1974 Johnson 85hp

Update: Tested spark and it had some random 7/16" jumps but I would call it a fail. Tested the stator resistance again, removed from the pack and it is ~100k ohms. Going to consider the stator toast. Going to swap motors with a 88SPL that rebuilt last spring and deal with this one in the spring when I sell the old boat.

Thanks for your ideas, much appreciated!

 

[emdsapmgr]

Re: 1974 Johnson 85hp

Not unusual for a weak stator to provide insufficient voltage to fire all the plugs on every rpm.

 

[JRegier]

Re: 1974 Johnson 85hp

Let me know what you plan on doing. I have a 1976 85 johnson that needs the block bored out but I'm thinking about parting it out. Stator looks pretty good and would fit anything 1973-1977 but I haven't had time to test.