1984 mercury 50 HP

[Qbanredneck]

Hi, was curious once you get lost in treading forums if this is a plug that shows water in cylinder, etc? Ordered left to right, cylinder 1-4. Compression is even 120 on all and spark test was good on all four. Starts right up and idles. Thanks for any suggestions

 

[Texasmark]

That engine is old enough to have a pin hole caused by corrosion in the cylinder wall......I had it happen on an engine with significant age, being used in salt water. A small hole would surely pass the compression test so I'd disregard that. With all the plugs out, shine a light in the hole and look at the piston crowns. If the one with the clean plug looks noticeably cleaner than the other 3 then you may be onto a water leak. Since Most Mercs have closed castings and no removable head, you can't blame water on a bad head gasket.

 

[The Force power]

Hi, was curious once you get lost in treading forums

I'm not sure what you are saying here??

Do a drop-down test on each Cylinder (while engine running unplug one cylinder at the time, to check for drop in RPMs)
Were the spark-plug all clean before? Clean all plugs & run/test again

Post results

 

[Qbanredneck]

Thanks all, tach is broken for now, I was able to record between all cables on and one off at a time didn’t notice any difference between recording and hearing it happening at the moment, I’m updating a picture after the plugs cleaned and testing done which shows plugs from cylinder 1-4 left to right. afterwards, I also sprayed some seafoam into carbs, smoked a lot and had lots of gunk come out lower unit, I also noticed the top carb had a strong suction while the lower I can cover completely and would not kill the engine. Guess rebuild time. Don’t see any water droplets on plug if that’s a thing, and can’t look into the holes without more work which I can always do...

****i meant getting lost in reading cause of all the info on the web between it could be water, reeds, etc...

first wire plug I see needs to be changed, shocked me, and was the hottest spark plug on there

I really appreciate any help anyone can give

 

[Qbanredneck]

Ok was able to look into the holes and all four have the same color, black, from second look at plugs maybe they look normal? Not sure if I’m looking to much into it

 

[QBhoy]

I’m not sure and maybe I am getting confused, but I can’t think that you even have an issue. If you have 120 across all of them, that’s great going.
Although I think you should notice a difference in the sound of it running if you choke one of the carbs though.
Plugs to me don’t look terrible for a 2 stroke and especially since you’ve run Seafoam through it. I’d get a new set of plugs and go enjoy yourself.

 

[Texasmark]

Now that we know you blasted with Sea Foam, google or archive check "decarb". Do it, get the smoke blown out good and then install new plugs.....ebay has great prices. Run it hard for an hour or so and if you still think you have a problem, come back.

 

[bert smith]

Hey Qbanredneck,

Any updates on this? i have an 84 brown band 50hp, and i have the same issue. it seems to be getting ~70% power, and the low plug is too clean. i'm pretty sure i'm getting water in the lowest cylinder. my compression is good.

i plan to pull the powerhead and replace the bottom exhaust gasket and the exhaust manifold/baffle gaskets