spark test

[Troyb56]

I have 1971 60hp johnson. Having trouble running. I tested all three sparks with automotive tester that starts at 0 -10-20-30. cyl 1 sparked good and strong at 10 and around 15 it wasn't as strong and a little intermittent. cyl2 strong at 10 and 15 and ever now and then on 20. cyl3 strong at 10 and 15 and some at 20. could someone tell me if this is or is not my problem. Motor will start at fast idle but will not idle down and run.

 

[Daviet]

Re: spark test

Spark should jump a 7/16" gap and be bright blue. Have you checked the compression?

 

[Troyb56]

Re: spark test

Yes all compression between 135 and 140. all 3 plugs where wet after checking spark

 

[Troyb56]

Re: spark test

I also just measured the spark gap and it is at least 7/16 or greater on all plugs. cyl 3 the best cyl2 then cyl1, but all are 7/16.

 

[Daviet]

Re: spark test

If the spark and compression are good the only thing left is fuel delivery. How long has it been since the carbs were overhauled?

 

[Troyb56]

Re: spark test

I just had all 3 carbs rebuilt. I have cleaned out the fuel filter screen, no help. The prime bulb primes good and all 3 carbs have fuel in the bowl. Thanks for the help, please stay with me

 

[Daviet]

Re: spark test

Can you define "trouble running", what is it doing exactly?

 

[Troyb56]

Re: spark test

I bought motor and the guy had it running on muffs, it ran fine, idled, shifted. I put it on the back of the truck and came home, put it on my boat and took it to the lake, motor would not idle when put in water, but would on muffs. Tried to adjust with no luck, since then I could pull the plug boots off of cyl. 1 and motor would not change. I finally got it to idle a little bit, but it would surge up and down with a little back fire. Took it to the lake again, and finally after fighting idle, i got it into gear, but just to run about 10mph it seemed, never would even get up out of the water.

 

[Daviet]

Re: spark test

If the spark and compression are OK, the idle should be set to 700-750 RPM in the water and in gear.
Try squirting some fuel mixture into each carb and see if #1 cylinder picks up.
Are the plugs in good shape and proper heat range?
If pulling #1 plug wire does not affect anything you either have no compression, spark or a fuel delivery problem on that cylinder.

 

[Troyb56]

Re: spark test

Is there a rpm gauge I can buy, my boat does not have one, compression is great and I just checked spark, it is ok. I am getting plenty of gas at carbs, as when motor is running I can choke out with my hand and fuel is plentyful on each carb. I did stop and talk to a mechanic on duty at a boat shop and he said just because a carb has fuel, don't mean the idle circuit is good, I am a little confused on what that means. If all carbs have fuel in bowl, could I eliminate the gas tank, fuel hose, prime bulb and fuel filter.

 

[Daviet]

Re: spark test

The mechanic means that the carbs have different circuits in them. The low speed circuit in the carb could be restricted and not letting fuel into the engine.
If the carb bowls are full of fuel, usually it means the fuel supply is OK.
Who rebuilt the carbs for you?

 

[Troyb56]

Re: spark test

A local boat mechanic, he also set the points. I am pretty handy with doing my own work, I have had the carbs off before. How many jets are in each carb and are they all removable to be cleaned, also if spraying the fuel through the carb while running doesn't pick up the cyl, carb might be ok,

 

[Daviet]

Re: spark test

Do you know what he set the points to?
Yes, if squirting fuel into the carb makes no difference, the carb might be ok.
Your low speed needle should be set at 1 1/4" out from lightly seated and then adjusted with the boat in the water and in gear. The high speed orifice is fixed, not adjustable.

 

[Troyb56]

Re: spark test

Idk what he set the points, but I will try working on the fuel issue with spraying the carbs. Motor will start everytime at fast idle, so I hope it is just a fuel delivery problem and not an electrical one, as I am getting good spark it seems. Thank you Daviet for the help, is there a way I can keep you posted and get some more advice

 

[Daviet]

Re: spark test

Just keep posting on this post with updates or questions.
Make sure the low speed needles are set properly.

 

[Troyb56]

Re: spark test

Ok Daviet, I am going to give you everything I tried. Working on it again today. As of now cyl 3 is the only one running this motor as I can pull off boots 1,2 and makes no difference. I checked compression again today cyl1 140, cyl 2 145, cyl 3 144. I went and got fresh gas. All 3 carbs full of gas in bowl. I sprayed fuel while running in cyl 1 and 2, no difference. all idle screws are set at 1 1/4 out. While running I did take the throttle linkage off cyl 3, the one thats running everything and advanced the throttle linkage and the motor revved, thats weird to me that something is running in these cyl, but when pull boots nothing. I put the plug from cyl3 into cyl1 just to check if it would then fire but no change. Prime bulb is strong when squeezed and when I changed gas, I left the drain screws out and primed and all three carbs getting good fuel. Spark gap was at least 7/16 on all 3 cyl, but was the highest on cyl3. Sorry for bouncing around here, cyl 1 and 2 plugs where wet with gas after pulling them, as cyl3 looked good. Fuel is spraying when throttle advanced. Rebuilt all carbs. well thats about it, whats next Admiral

 

[Troyb56]

Re: spark test

Now I think I am getting somewhere, I pulled the plugs and they never was gapped, as soon as I gapped to .30 cyl 1 and 2 fired right up, but then cyl 3 wouldn't, why would this be, cyl3 had the strongest spark gap of all. I pulled plug back out of 3 and gapped to .20 , it picked up, but still not as strong as 1 and 2 when pull off boot, but motor is now running much better, but still can't adjust carbs to get a smooth idle. Should I gap that plug even lower.

 

[Daviet]

Re: spark test

The plugs should be gapped to .035. What plugs are you using?

 

[Troyb56]

Re: spark test

I am using the champion plugs that was recommended I think L77. I can see gapping the plugs fixed the cyl1 and 2, but why is cyl 3, the one that was running by itself now not, It was gapped at .40 out of the box and running, when I gapped to .30 it stopped running, then I went to .20 and it is running again.

 

[Daviet]

Re: spark test

Maybe a defective plug? I would gap all the plugs to .035 and see how it runs. If #3 is still a problem, switch it to another cylinder and see if the problem moves.