'79 evinrude 100hp- one fouled plug!

[dumb tom]

I took this old boy out last week and I could not get above 3000 RPM. I decided to check the plugs and review the throttle cable connection. When removing the old plugs, I noticed that the upper starboard (#1//) plug was wet while the others were dry. I installed new plugs (NGK BR7HS gaped to 035) and it started right up on the muffs. After about 5 to 10 mins. I shut it off and then removed the new plugs. The #1 plugs was wet, but all the others looked brand new. To check if I was getting spark, I restated the motor with plug 1 disconnected. It ran but very rough.

Anyway, the questions are as follows.
-Is this a common problem? If not, what fixes would you recommend
-Should I use a different plug on #1? If so, what do you recommend? Would the surface gap be better?
-Should I replace the #1 wire?
-Should I rebuild the carbs, paying special attention to #1 throat?

All ideas are welcome (except getting a new motor)

 

[F_R]

Check the compression. There may be internal damage on #1

 

[emdsapmgr]

You've got the wrong spark plugs in that engine. Should be Champion QL77JC4's. After checking the compression, check the spark on #1. If that plug is wet, it may not be firing. If not, it is probably not contributing to running the engine.

 

[dumb tom]

Thanks! I will check compression, probably on Wed., and let you know. #1 is getting some spark as it runs real rough without it (while idling), but smoother with it.

 

[dumb tom]

Sorry it took so long to reply. Here is the compression results:
cyl 1 115
cyl 2 115-117 #
cyl 3 120
cyl 4 120
# ran multiple tests, one test (after running engine)showed #2 up to 115.

Is it okay to run one surface gap plug and three pronged plugs?

 

[ondarvr]

What makes you think you need to run a surface gap plug in that cylinder?

 

[emdsapmgr]

The spark-gap test will tell you a lot about the quality of spark on this engine. You can probably rent one from a local auto parts store. Compression is close to normal. Should run with those numbers. 125 is normal. Make sure none of the plugwires are grounding out on the block or the lower cowling latches.

 

[racerone]

Remove cover on front of carburetors.-Run the boat in the water , in gear at full throttle.---Shine a strong flashlight into carburetor bores.--Observe / compare amount of fuel coming up the main jets.

 

[dumb tom]

I will do a spark plug test in the next day or two. I assume I can test at both idle speed and full speed, I was wondering about the surface gap plug, because someone referenced it (Should be Champion QL77JC4's) and I know the original plugs were surface gap. I do not want to get into a NKG vs, Champion discussion.

 

[emdsapmgr]

The 79 140 hp engine was the only V4 crossflow which used the center fire plugs that year: UL77V

 

[racerone]

A " cold running " cylinder will show a fouled plug.---It is not a plug problem !

 

[dumb tom]

First of all, it is a 1972 Engine, not a 1979. My fingers do not always do what they are told anymore.

I performed a spark test on all the wires yesterday. The wire for #1 showed consistently a weak spark (and sometimes intermittent) whereas #4 had a consistent strong spark. (2 and 3 were consistent but not as bright as 4). Can one still get spark wires for this engine? Any place helpful? Do I have to remove the flywheel to remove the wires? {remember the fingers and the year of the engine} Can I make replacement wires? What should I look for? Perhaps the above items are addressed in another post /sticky note. Can anyone point me in the right direction?

Thanks for all your help!

 

[racerone]

The wires are screwed onto the cap.--Metal core 7mm wire and it is available at most boat shops.-----Remove flywheel and clean up the rotor, cap, inspect anti reversing spring too.