1979 Johnson 100 HP carb question & magneto

[ceddon46]

Motor is a J100TLR79S

Having fuel issues carbs flooding , after pulling the plastic breather cover off exposing the carbs , I noticed while turning over the motor there was fuel coming out of a tiny port in the bottom right corner of the metal plate that is attached to both carbs if your facing the motor, and after inspection there is a fuel line attached to this port it is not even on the carbs so why would there be a line attached to it and fuel coming out of it.. So I am asking what is this for ? the gasket on the fuel pump was faulty allowing in air would this allow fuel to come out of this port ?... Also While putting a new ignition switch in I got my wires crossed and put 12v to the magneto kill wire would this hurt the magneto ?

 

[Joe Reeves]

Re: 1979 Johnson 100 HP carb question & magneto

If you threw 12v to the black/yellow wire, you probably blew the powerpack. Hopefully you were one of the lucky ones.

Your statement of... "there was fuel coming out of a tiny port in the bottom right corner of the metal plate that is attached to both carbs if your facing the motor, and after inspection there is a fuel line attached to this port it is not even on the carbs so why would there be a line attached to it and fuel coming out of it."

That statement (above) is confusing to me. I'd need a better explanation of that problem.

 

[ceddon46]

Re: 1979 Johnson 100 HP carb question & magneto

I was pumping the bulb up and it would not get hard , after inspection there was fuel coming out around cap on fuel pump when I was squeezing bulb so I replaced the gasket and pumped it up , tried starting motor and it would not crank figured I flooded it so pulled black plastic cover off to expose carbs , lots of fuel was in the breather area , so this made me believe it was flooded so tried spinning engine over with out any throttle and when I did this I noticed fuel coming out that port to the botom right of the breather plate , looks like the rubber line attached to it goes under the bottom carb maybe connected to the manifold cant tell with out tearig it down further... also when I tilted motor all way up lots of fuel ran out of both carbs ... and on the power pack issue , to check power pack I just check to see If I have spark correct ?

 

[Joe Reeves]

Re: 1979 Johnson 100 HP carb question & magneto

Okay, you're speaking of the hose that leads from the carburetor face plate to the bottom main bearing area of the powerhead. That allows the excess fuel/oil mixture that may collect in the face plate assembly to drain back and lubricate the bearing(s).

You say the engine would not crank... if the starter was turning the engine over, it was cranking, it just wasn't starting. Best to use the proper term to avoid confusion.

Lot of gas in the breather area? Leave the face plate off and pump the fuel primer bulb while observing the carburetor throats. If fuel flows from any carburetor, remove, clean, and rebuild both of them.

What is the compression readings of each individual cylinder?

With the s/plugs removed, rig a tester so that you can set a gap of 7/16" for the spark to jump... the gap is important! The spark should be a strong blue lightning like flame... a real SNAP! Is it?

Spark plugs should be Champion QL77JC4 plugs gaped at .040 .

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

You can use a medium size philips screwdriver 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

 

[ceddon46]

Re: 1979 Johnson 100 HP carb question & magneto

Just purchased this boat and going to do all the test this weekend and will advise on compression and so on already purchased carb kits and 4 coils for it and plugs ( did get the champion QL77JC4 ,s ) but gaped them at .030 like I have read on web but you are saying .040 ? what started all this was after I purchased the boat the motor started and ran fine on a hose but when put in lake it would not idle very good and die as soon as put in gear so was going to run all the test on it when got it home but lost key on way home and had to replace ignition switch previous owner replaced the ignition wire's and had color wrong at the switch making me put 12v to kill circuit , after replacing switch correctly engine would not start and the leak at fuel pump and flooded carb issue started..

PS sorry about my southern lingo

 

[Joe Reeves]

Re: 1979 Johnson 100 HP carb question & magneto

QL77JC4 ,s ) but gaped them at .030 like I have read on web but you are saying .040 ?

The original recommended gap back in 1973 when that ignition system first came into being was .040. It was later changed and recommended in the late 1990's to be .030.

One or the other may provide improved performance either at idle or at full throttle... it varies from engine to engine. However, .030 is good and when you get the engine running good, then you can experiment.

 

[emdsapmgr]

Re: 1979 Johnson 100 HP carb question & magneto

As usual, some great tips from Joe. Any engine will seen to run just fine when sitting on the trailer, running on the garden hose. There is no exhaust backpressure. Dunk the boat in the lake, and the exhaust is 20" underwater. Now you need the carbs and ignition to be running perfectly or it won't make hp and may die-just as you indicated. A low idle speed can also cause poor idling.

 

[ceddon46]

Re: 1979 Johnson 100 HP carb question & magneto

Ok found out problem why it would not start last night the black/yellow wire on controls got pinched and shorted out while I was putting in the new ignition switch fixed that problem and put new coils on it and new plugs in it cleaned out the fuel filters had some trash behind the screen in fuel pump cap, set plugs at .030 has an awesome blue spark that jumps the 7/16 of an inch so didnt knock out power packs last night did a compression check all were 120 psi , so I started it up ran great while fast idle was up started lowering fast idle lever after about 10 min , when it got to about 1/4 of the way from being all way down the engine started spurting and spit out exhaust and died got to real low rpm's , started right up again and sounded great no problem as long as fast idle is above 1/4 of the way full , so going to rebuild carbs in the morning and read up on how to set idle rpms

 

[emdsapmgr]

Re: 1979 Johnson 100 HP carb question & magneto

When that engine idles, the carb butterflys are closed and it will draw fuel through the very small idle passages. If these get restricted due to dried fuel gel, it won't idle correctly. Once you crack the throttle even a little, the engine will start to draw fuel from the mains and will probably run fine right up to WOT. Cleaning the carbs is a good idea. You'll need a fuel cleaner product like Gumout in order to clean any dried fuel.

 

[ceddon46]

Re: 1979 Johnson 100 HP carb question & magneto

ok both carbs are rebuilt starts right up but still want idle runs fine with warm up lever up ? is there a good link as to how to adjust the idle speed on this motor ? J100TLR79S .. carbs was really clean by the way still cleaned and blowed them out a rebuilt

 

[emdsapmgr]

Re: 1979 Johnson 100 HP carb question & magneto

The idle rpm's are set by adjusting the large screw on the spark advance lever. By screwing it in/out, the actual idle timing of the engine is adjusted. That's what sets the idle on that engine. Set the idle when the boat is floating normally in the water and it's shifted into forward gear. Set the idle rpm's at 650 to 700 rpm's. You can't set the idle on the trailer.