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Author	Topic:   1984 Johnson 70 Carburetor Leak
cbgann	posted 07-04-2011 10:57 AM ET (US)         At idle, fuel blows out and leaks out all three carburetors [on a 1984 Johnson 70-HP outboard engine]. No fuel leakage with engine off and pumping ball very hard. I know a chipped reed valve can cause, this but I think that would be isolated to one carburetor. Could bad crankshaft seal or leaking crankcase seal cause this? Any experience or ideas? Thanks, Bill
Tohsgib	posted 07-04-2011 12:16 PM ET (US)             All three is a weird one and would isolate reeds as not being the culprit, as I doubt all three sets would fail at once. Gotta talk this one over with some peeps.
captbone	posted 07-04-2011 01:33 PM ET (US)             Carb vent clogged.
cbgann	posted 07-04-2011 06:45 PM ET (US)             Rebuilt and soaked all 3 carbs pvernight, Blew gumout threu all passages and vents, still same problem?
captbone	posted 07-04-2011 08:00 PM ET (US)             Did you check the hoses for vent? Is the fuel spiting out or overflowing? Any chance your float height is off? It should be level when the carb is upside down and the bottom bowl off.
Tohsgib	posted 07-05-2011 12:08 AM ET (US)             Float level on all 3 carbs is extreme but maybe possible. I am thinking lower seal, etc that is allowing pressure to build at slow speed but not at higher....still researching.
cbgann	posted 07-06-2011 01:29 AM ET (US)             Thanks guys, float levels looked good. Parallel with AND approx 1/8" gap. Could not cause leakage by over pumping the bulb, usually the telling sign of float set too high. Not sure what hose vent you are referring. Each carb has main fuel in and primer line iN. jUDGE, ARE YOU THINKING THE LOWER SEAL WOULD AFFECT ALL 3 CYLINDERS? tHANKS, bILL sorry about the cap lock. [Why didn't you just retype that sentence?--jimh] Also, engine will stall out at idle trimmed down, trimmed up it will run but fuel spits and runs out the throat.
Tohsgib	posted 07-06-2011 11:58 AM ET (US)             How does it run on the muffs? If t runs fine and does not spit at idle on the muffs my $$ is on the lower crank seal. When in the water the water level raises almost to the exhaust holes because of the way the boat sits. This makes exhaust much harder to exit because it has to pass through all that water in its way to the prop. The increased pressure if the seal is bad will sometimes make exhaust go out the carbs instead of down or suck in water. If it runs fine on muffs and on plane is because the water level is not there to produce the backpressure. Unfortunately you need to remove the powerhead to replace at $15 part.
cbgann	posted 07-06-2011 08:03 PM ET (US)             Owner decided not to wait for us and went the high $ route. Took back to the marina where he bought the 15 and 70hp and told them to fix it. Will find out if he ever ran on the hose.
Tohsgib	posted 07-06-2011 08:57 PM ET (US)             Huh? Please explain! Was this your engine...prospect/friend? Please in the future let us know. Might be as simple as "walk away" instead of me asking 4 different mechanics what they think for somebody we don't know, etc.
pcrussell50	posted 07-06-2011 10:21 PM ET (US)             When you rebuilt the carbs, did you remove and clean under the core plugs? IMS, if those are blocked, it can cause the issue you are describing... although again, it seems odd that it would happen to all three at the same time. Then again, if something like ethanol melted of a sizable amount of the inner wall of the fuel line, it could have quickly sent blockages to every one of those tiny little holes under the core plugs. -Peter
cbgann	posted 07-07-2011 08:56 AM ET (US)             Sorry Judge, Boat owned by a good friend in Ct who bought a 15' classic whaler based on my recommendation for the only classic boat that appreciates in value and is in my opinion, the best hull that Whaler ever produced along with the Mercury CE designed 3 cyl OMC. As far as the core plugs; no did not remove but was able to blow gumout thru all the core pasages and verify that the 3 ports in top of carb bore were open. also, used dental pick on the bore holes. He returned the boat to the selling dealer with the question of reed valves, crankcase seal leak and possible crankshaft end seal issue. Dealer promised they would rectify and return within 2 wks. He is now aware of the Continuous Wave community, plans to get involved and appreciated the help. Bill

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