Johnson 135 still misfiring (1976)

[derek4325]

You guys are probably getting tired of me posting about this engine, but to be fair so am I lol. Anyways I had the boat out the other day and it ran beautiful all day except toward the end. All of a sudden it started to misfire and getting progressively worse almost as if a spark plug was beginning to foul. But how or why? I can't believe it's the timing because it ran fine for the most of the day. And it has all new coils, plugs, wires, boots with dielectric grease, new power pack. They are surface gap plugs so I couldn't possibly mess up the gap. The gas and oil mixture is perfect. I have not done a spark test because it ran perfect beforehand, and I really don't know what's involved in a cylinder drop test. Could water be getting in one of the cylinders? Do I just check for water on the plug? If water is getting in what gaskets should I replace to correct this issue? Thanks, derek

 

[racerone]

Testing 101----Do a compression test first.-----If ok then hook up a timing light to # 1 and take boat for a spin.----Observe the light when motor misses.-----Repeat the test with # 2, 3 , 4.-----Also use a STRONG flashlight to look into carburetor bores and note fuel coming up the main nozzles when motor acts up.

 

[ahicks]

I haven't had very good luck with surface gap plugs. Are those recommend for this engine? If not, that's where I would start. A fresh set of resistor type plugs.

 

[derek4325]

I haven't had very good luck with surface gap plugs. Are those recommend for this engine? If not, that's where I would start. A fresh set of resistor type plugs.

Yep. The manual calls for champion ul77v so that's what I put in

 

[mrcj001]

I had this exact same engine and mine thru a piston ring.... check compression.

 

[derek4325]

Update. All my fault. While we were anchored yesterday I decided it would be a good idea to adjust the idle screw since it was stalling every so often at idle. Well after I examined it today I actually adjusted the timing... oops! It was shortly after that where the engine was running funny. I took a compression test to make sure I didn't harm anything and luckily I am around 125psi on all 4. I timed it using the Joe reeves method and timed it to 16degrees (service manual calls for 20). Going to take it out tomorrow morning and test it once again. Wish me luck and ill post with an update. Dumb mistake i know.

 

[derek4325]

Update. I tried it out today and it ran TERRIBLE. I soon came to find out that the coil on cylinder #2 is arcing to ground. Brand new coil (Sierra marine) go figure. It was arcing right where the wire goes into the coil (already had dielectric grease around that area) tried all the liquid electric tape in the world and still no luck. It would just keep arcing in a different spot. So I broke down and ordered a new OEM one and I'll try that. I have never had something as simple as plugs/ wires/ coils give me so much trouble before. But it is what it is I guess lol.