1980 johnson javalin 100 hp help

[1976 sleekcraft]

I have a 1980 johnson 100 hp.It is bogging down under load.Comp is good.110 on all cylinders.Has spark.Rebuilt carbs.Bottom port cylinder seems to be dead when I pull wire, but it has spark.Any help would be much appreciated.Thank you!

 

[Bosunsmate]

Have you checked the timing on that cylinder?
Also remove the sparkplug, clean it and then put it back in and ground the wire, dont hook it back up. Run the motor for 10 seconds. Remove the spark plug, check that it is wet with fuel. If its wet light it to make sure its fuel. If water gets in from a broken gasket etc the plug will be wet from water so you need to light it to check its combustible fuel.
You should also check all your other sparkplugs for their combustion colour, check evenish between all cylinders

 

[1976 sleekcraft]

Thanks for the reply.I looked at the plugs no water seems to be getting in.Plugs are wet with fuel and oil, but the dead cylinder is dry.I dont seem to notice any odd discoloration in any of the plugs..not sure. How to check timing.I come from automotive background.know how to check timing on inboard but not outboard.not sure if is the same procedure.Outboard kicking my butt!

 

[Bosunsmate]

ok dont worry about the timing yet, thats just a rare chance of being the problem.
Sounds like the dryness is the issue
Have you held a dollar note in front of the carbs too check they are all sucking evenly?
Bottom port- would that be the very bottom cylinder below the bottom starboard? ( if so a worn lower seal can cause that cylinder to run lean)

 

[1976 sleekcraft]

Yes.I believe we are talking about the same cylinder.if looking at the motor it will be the very bottom cylinder port side.The carbs seems to be sucking good, when I put my hand over it, it spills fuel.A friend mentioned a seal on the crank on the bottom of the powerhead, but I wasnt sure if that could really be the problem.Didnt want to remove powerhead unless it was a last resort.I wanted to be sure rather than to guess, because he was not positive that was the problem.

 

[Bosunsmate]

You could swap the carbs over to rule them out.
Also check for any leaks in hoses or bypass cover gaskets.
Also id lube up that cylinder before you do anymore testing
I decide whether its a lower seal by elimination.
Hard to tell if its the other cylinder making that carb spill fuel

 

[Bosunsmate]

By the way you dont need to split the crankcases to change the seal, you just need a good pulley to lift the motor off with everything still attached. Thats if it is the seal, ive never heard of a way to be 100% sure unfortunately

 

[1976 sleekcraft]

I will try the carb swap, and check bypass cover gasket for leaks.Its good to know at least I don't have to split the case to change seal.I will lube the cylinder like you recommend too.I will keep updating incase someone else has this problem in the future.Thanks for all the advise.I really do appreciate it.