Omc 1979 85hp v4 dry spark plug

**Turtleherder** · 10-05-2021, 12:36 PM

This is about a dry plug on number two cylinder (top left). I bought an old fishing boat last year with a 1979 Johnson 85hp v4. The carbs leaked like crazy and two of the coils showed signs of melting down. I rebuilt the carbs and replaced all the coils, wires and plugs. It ran fine last year. This year it started out running fine but then seemed to lose power. It’s off about 800 rpm’s on wide open throttle. I checked for spark on all cylinders and each was firing. I pulled the carbs and made sure nothing clogged up a jet and found both carbs to be clean. I put new plugs in and ran it again with the same result, down on power. When I pulled the plugs to look at them number two, top left, was completely clean. I thought it might be a water leak but the piston is still black on top. Anybody know what could be causing this?

**James45157** · 10-05-2021, 01:04 PM

run a compression check on all 4

**Turtleherder** · 10-05-2021, 01:14 PM

Originally Posted by James45157

run a compression check on all 4

I should have said I did that. Number two is 120. The rest range from 117 to 114. Number two is actually the best.

**Forkin' Crazy** · 10-05-2021, 04:43 PM

So number one is good? They of course share the same carb. You blew through the passage ways the mains go through the bowl and carb body? I have heard of a main that got loose and backed out restricting fuel.

So you can tell it is missing? Have you pulled the wires off one at a time while running?

**Turtleherder** · 10-05-2021, 05:28 PM

Originally Posted by Forkin' Crazy

So number one is good? They of course share the same carb. You blew through the passage ways the mains go through the bowl and carb body? I have heard of a main that got loose and backed out restricting fuel.

So you can tell it is missing? Have you pulled the wires off one at a time while running?

yes number one is good. That’s what’s got me really stumped. How is number one wet and running but number 2 is not? (No jokes about aging). I took all the jets out and blew out all the passages, nothing there. I have pulled the wires one at a time and like most v4’s it runs good on three but when I pull another to knock it down to two and it stumbles. I checked the spark and all four jump a 7/16 gap. I also checked the reeds when the carbs were off and none have chips or are broken. For me it’s a real wtf?

**H2OPERF** · 10-05-2021, 05:38 PM

A quick check i often do when your not totally sure what going on with a motor at first is Run it on the hose with the air box cover off and give the throttle a quick rap while looking into each carb and you should be able to see somewhat equal amounts of fuel coming out of the emulsion tubes in each one, its just an easy check for a completely clogged carb without pullin much apart...

**Turtleherder** · 10-05-2021, 05:55 PM

Originally Posted by H2OPERF

A quick check i often do when your not totally sure what going on with a motor at first is Run it on the hose with the air box cover off and give the throttle a quick rap while looking into each carb and you should be able to see somewhat equal amounts of fuel coming out of the emulsion tubes in each one, its just an easy check for a completely clogged carb without pullin much apart...

.

Good advice for the future.

**Forkin' Crazy** · 10-05-2021, 07:11 PM

Originally Posted by H2OPERF

A quick check i often do when your not totally sure what going on with a motor at first is Run it on the hose with the air box cover off and give the throttle a quick rap while looking into each carb and you should be able to see somewhat equal amounts of fuel coming out of the emulsion tubes in each one, its just an easy check for a completely clogged carb without pullin much apart...

Great idea! Or even better in the lake and have someone run it for you so you can watch.

That is crazy... Usually when mine were dry, they stuck!

**Turtleherder** · 10-05-2021, 07:43 PM

Originally Posted by Forkin' Crazy

Great idea! Or even better in the lake and have someone run it for you so you can watch.

That is crazy... Usually when mine were dry, they stuck!

I figure something must be getting through, at least a little, to keep the cylinder lubricated. But that damn clean, white plug has me baffled.

**James45157** · 10-05-2021, 08:20 PM

i had one years ago a guy brough in found a gasket had went bad and was holding a reed open would not run on that cyclinder

**Turtleherder** · 10-05-2021, 09:19 PM

Originally Posted by James45157

i had one years ago a guy brough in found a gasket had went bad and was holding a reed open would not run on that cyclinder

I was afraid it might be something like that. Not looking forward to trying to find out for sure.

**Turtleherder** · 10-06-2021, 09:45 AM

Well it looks like James might be right. Thanks. I took the carbs off again and looked at the reeds with a very bright flash light. This Time didn’t just look for failed or chipped reeds I looked for one that might be slightly open. Yep on the very top row I have one that is open about 1/32. So is there a way to suck it back? I am soaking it in de-carbon spray. Any other methods besides tearing the front off?

**FMP** · 10-06-2021, 09:47 AM

CCM reeds

**Turtleherder** · 10-06-2021, 04:05 PM

James was right. I took off the front of the motor and took out the offending reed block. The one reed was actually more like 1/16 of an inch open. I cleaned up the block, flipped the reeds over and across and put it back together. Fired it up on the hose and now I have a wet number two plug and power from all four cylinders. Thanks again James for pointing me the right direction.