115HP 1,2,3 Wet, 4,5,6 dry

[Snagged]

Fun...Fun...Fun,

She's a 1984, 115hp, in-line 6 with 3 carbs.
Can't get her to idle below 1200rpm, rpm surges up, runs rough.
The plugs and cylinders for 1, 2, & 3 are wet, but the plugs and cylinders for 4, 5, & 6 are dry. I pulled and cleaned the lower and mid carbs and reinstalled, but it made no difference. Strange that 3 is wet and 4 is dry since they share the same carb, so I'm assuming it's an electric issue but I'm getting spark. Coils, stator, large hammer????? Help.....

Thanks

 

[Snagged]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Ran a compression test today and got #1-130, #2-130, #3-130, #4-125, #5-125, #6-125.
Also hooked up an inductive pickup from my tester and had spark to all six cylinders.
Could the previous owner have mixed up the firing order?????
Do the plugs & cylinders match up with the coils from top to bottom. So if #1 plug is at the top of the motor should it match up to the upper most coil at the top of the motor and then continue that pattern the same way all the way down?

I have spark, I have compression, I have clean the carbs....ideas anyone....

Thanks,
Rick

 

[anzomcik]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

The plugs wire do follow the cylinders down in order, as the top coil goes to the top cylinder... But that is not the case from the switch box to the coil. The top switch box controls the odd cylinder and bottom controls the even cylinders.

I fought with my L6 all summer, until i figured out my problem. I worked on my motor mostly by my self and used an inline spark tester. Well it was reading i had spark, but when i had a helper holding the plug to the motor head i was not getting spark. It took a long time to stumble on that. I could not believe it because i replaced the whole ignition in the spring. Moral of the story unless you check it do not assume because its new it works

The next test i did was one for more of personal satification than anything but i can help. I preformed a leak down test on all the top 5 cylinders (#6 is hard to reach) what the test tells is amount of leaking through the rings. I preformed mine at just above the transfer ports to see if i have a tapered cylinder.

Also when it is running have the hood off and look with a flash light down the carbs bodys and see if there is excess fuel being spit back, you are checking the reeds by doing this. Reeds are important for a good idle.

If i think of more things i did ill post more. Have fun

 

[Snagged]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Well I replace all the plugs and re-check for spark, this time with the plugs out of the cylinders and grounded. I got spark on all six. I then reinstalled the plugs and got her started with the usual hassles. Still ran like crap and would stall below 1000rpm. I kept her running for half an hour or so, sprayed in some carb cleaner....... at this point why not, when I sprayed in the top carb the rpm's went up, mid carb had a minor increase in rpm's, and no diff on the lowest carb, ran it some more. Also tried squeezing the gas bulb, no effect.
I have now pulled all the plugs again to check their condition. So same thing again, 1, 2, & 3 are wet, a little oily and look like they have been firing; 4, 5, & 6 are clean and relatively dry like they haven't been firing. But I saw the plugs spark when testing. It's like the lower coil pack is bad, but why the spark when cranking & testing and not when running?
Could it be two bad switch boxes, with the upper having #5 bad, and the lower having #4, & #6 bad, or does a failed switch box always lose all three cylinders?
Any help....please, I've got lake trout fever.

 

[anzomcik]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

With this ignition the spark is independent from other spark. So say if #4 goes down it only goes down taking no other cylinder with it.

Where are your idle mixtures set? mine are 2.5 out on top, 2.375 mid, and 2.25 on bottom. The gas we are getting now is very bad and makes it hard to tune these motors.

Also whats the sondition on the gas you have, i had a little water in mine and i had to pull the tank and empty the gas and let her dry out. I could see alot of crap in mine, and water droplets. It would be worth checking that out.

How are your floats, another problem i had was my floats had a very small hole in two of them and would let fuel inside of them, then they did not float very good anymore causeing a flood gate to open and poor running. Make sure your carb gaskets are good also.

Long shot here, look at the motoro case gasket it runs vertical on the motor where the motor splits, is there any oily greesy wet look? there should not be but a bad case gasket is not good. Very unlikly but it takes 2 secounds to see. Ill post more when i think of more stuff

 

[hkeiner]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

I got spark on all six.

when I sprayed in the top carb the rpm's went up, mid carb had a minor increase in rpm's, and no diff on the lowest carb, ran it some more.

If you have spark but no response when spraying fuel into the carb throat, my guess is that the reeds for the suspect cylinders are bad causing fuel to be not sucked into these cylinders. Just a guess but worth checking out.

 

[Snagged]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Any idea on how to check the reeds?

I'm staring to think it's the three coils; sparks out of the cylinder, but not under compression, maybe just a tad too weak.

 

[j_martin]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Compression effectively increases the gap. If it sparks a long distance (7/16" or more" out of the cylinder, it will fire the plug under compression.

Use a spark gap tester to determine spark quality, not a spark plug.

With 3 wet, and 3 dry, I would suspect the wet ones are out of order in firing.

hope it helps
John

 

[Snagged]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Decide to gamble a couple of bucks and ordered three new coils. Ran out of time to go and switch them around to check or I would have missed the ship out time.
So either way I'll know tomorrow if it's three bad coils.

Btw, should I be getting an oily watery emulsion out the exhaust when running with muffs?

 

[CharlieB]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Are the lower three plugs really dry OR are they steam cleaned?

Look into the plug holes, what do the piston domes look like?

You could have a leaking gasket in the exhaust side allowing water into the lower three.

Idle poorly but clears, or gets better once rpm comes up considerably?

Pull the exhaust plates off, carefully, aged bolts often get like me, creaky and cranky, may snap on you!

 

[Snagged]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Could I have good compression and still have a leaking gasket in the exhaust side?

Rick

 

[CharlieB]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

YES

The water entering the cyls at idle could explain the miss at idle and your spraying fuel in making no difference.

Does this motor seem to have power at half throttle or more?

Less water, the plugs get a chance to 'dry out' fire and all seems well, until you slow down.

Water is entering thru the exhaust ports, no change in compression.

Did you look in thru the spark plug holes yet?

What do the piston domes look like, steam cleaned, shiny aluminum?

 

[Snagged]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Well...... your probably right and I have a lot to learn.
4, 5, & 6 look real nice.......too nice.
Guess I should have held off on putting in the new coils and plugs, and R&Ring the carbs, and putting in the waterpump because it didn't make any difference anyway. And when she gets up to about 2500rpm there is a definite instant jump in power and the rpm will spike to 4000.
To top things off...................I burnt up my new water pump, total burnt toast with rubber jam on top. Yup, I was just a bundle of joy & bliss for I knew I had found nirvana.
Anyway, thanks Charlie, & the guys for help'n.
Think I'll pickup an owners manual before I tackle this one.
And to the man that knowingly sold me this floating lemon tree.....your turn will come.

Rick

YES

The water entering the cyls at idle could explain the miss at idle and your spraying fuel in making no difference.

Does this motor seem to have power at half throttle or more?

Less water, the plugs get a chance to 'dry out' fire and all seems well, until you slow down.

Water is entering thru the exhaust ports, no change in compression.

Did you look in thru the spark plug holes yet?

What do the piston domes look like, steam cleaned, shiny aluminum?

 

[CharlieB]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Consider this a learning experience.

You are still getting off cheap.

Once you get this motor running you'll understand why so many wouldn't even think of running any other.

Old Merc RULE!

 

[hkeiner]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

Another possible lesson is to avoid replacing expensive parts on a hunch without first troubleshooting to determine if the part is actually bad. The only reasonable exceptions to this rule is performing normal maintentance stuff. This is a lesson that I have learned through experience...

 

[Snagged]

Re: 115HP 1,2,3 Wet, 4,5,6 dry

I was fairly sure it was the coils since everything seemed to point that way at the time. And I have been promising my kids we'd get out this year and go camping and fish like we have in other years....just needed to get the motor going. Well now that it's September, and this motor needs more work, it looks like we're done for another year and I feel bad I didn't come through for my kids, but that's life for a "do it your selfer" on a budget.
At least I think that this is the right boat for my needs and I'll be ready for next season with this motor fixed or replaced.

Rick