90HP Johnson has one dead cylinder

[BoatBuddy420]

I have a '86 90Hp Johnson VRO and the #2 cylinder won't fire. I have spark, (I took the plug out and layed it against the block). I have compression, all cylinders at 125 PSI. When I take the #2 Plug out it has gas/oil mixture on it but it has no signs of any combustion, all the other look good\little rich. The Oil injector is disconnected and the oil inlet pluged. I took the heads off and the #2 cylinder had little to no carbon deposits but the other 3 had a normal amount. I Changed the head gasket and the water jacket gasket. I rebuilt the Carbs, installed all new fuel line (from tank to carb). Changed the plugs 3 times with new ones. <br />Someone PLEASE help me!

 

[JB]

Re: 90HP Johnson has one dead cylinder

Howdy, BoatBuddy.<br /><br />There is a pretty good chance that you have a bad reed on the #2 inlet to the crankcase. That's where I would look first. Also possible is some other failure that prevents crankcase pressure scavenging.. .a gasket or seal.<br /><br />If the reeds and sealing are good, I would overhaul that carb. You have to take it off to inspect the reeds anyway. It is possible for only one barrel of those two-barrel carbs to gum up and feed too lean a mix to one cylinder.<br /><br />Good luck and let us know what you find.

 

[BoatBuddy420]

Re: 90HP Johnson has one dead cylinder

Thanks for the reply JB. <br />I just fininshed rebuilding the carbs today and putting them back on. I looked at the reed valves but i'm not to familiar with them. there were 3 grey flaps and i slightly pushed on them and they all went in a little bit. Does the fuel from the top Carb go to the #1 and #2 cylinders straight or in a cross pattern?

 

[mrm]

Re: 90HP Johnson has one dead cylinder

Double check the ignition. May have spark at idle or no load, but lose it when you load it up.<br /> Get a manual and study it.<br /> Good luck and have fun.<br /> MRM

 

[kenthrussell]

Re: 90HP Johnson has one dead cylinder

Well had sort of a similar problem with my merc intermittent firing on one cyl. found the problem was where the plug wire goes into the coil was all corroded or should i say oxidized or the proper term is a corona from the high voltage, from the moisture ,,,,you know how copper goes when exposed to the elements or brass . cleaned it up and then siliconed the wire then plugged back into the coil and now works great. checked the other 5 cyl. and did the same,

 

[DJ]

Re: 90HP Johnson has one dead cylinder

Boat Buddy,<br /><br />Are you SURE you have the spark plug wires going to the right plugs. Each cylinder has its own coil. The wires aere long enough to go to the adjacent cylinder.<br /><br />Why do I ask this? Because I crossed them once and kicked myself for an hour after figuring out why it wouldn't fire on one cyl. at the right time.

 

[clanton]

Re: 90HP Johnson has one dead cylinder

Check the isolation diode in the power packs.

 

[BoatBuddy420]

Re: 90HP Johnson has one dead cylinder

I just took off my intake manifold. My reed valves arn't chipped but how do i check the valve stop and the valve clearance?