1972 18 hp Evinrude keeps flooding an backfires

[eloham1979]

Okay I will start from the beginning I have a 14 foot boat a friend lent me an my son for the summer he said the 18 hp Evinrude had not been run for a few years but he had bought a carb kit an said that should get it going I cleaned the carb in berry man an then in my ultra sonic cleaner an then installed all new kit I had to clean the points up an I noticed the upper seal leaking there was a lot of oil in an around the points so I removed the stater plate cleaned everything well an replaced the plug wires an points an condenser an put coils on it so ignition system is now all new I got it fired up it smoked like a pig for about an hr an then cleared up an ran good I thought I was about ready for a water test the next day I cranked it again just to see how close I had the carb adjusted it started on about the 4th pull but was backfiring but only on low end throttle smooths out good on upper end I noticed fuel in the pan under engine an checked the hoses this fuel is literally leaking out of the intake manifold I was told it was the reeds causing this so I bought 2 new reeds an neww gaskets an put them in an just to rull out the carb I turned it upside down an put my little mighty vac to it an pulled 15 inches of vacum an let it sit it held it just fine an I left it almost a hr an it did drop to 14 but considering I just had a hose stuck on it I figured that's not bad I also did the same to the fuel pump on the block I pulled a vacum on it the diephrams are fine an I checked it at the block it's good I put it all back together an it cranks right up but after about 10 minutes it goes to leaking fuel out the intake an out the exhaust I did a compression check an have 110 pounds on upper an lower cylinders it has great fire white an blue very strong you can here it crack when you spin it not sure what else to check I also checked the key way an have put a new one in any help would be great

 

[HighTrim]

Re: 1972 18 hp Evinrude keeps flooding an backfires

Where exactly is it leaking?

 

[HighTrim]

Re: 1972 18 hp Evinrude keeps flooding an backfires

Did you ever change the upper crank seal?

 

[eloham1979]

Re: 1972 18 hp Evinrude keeps flooding an backfires

it is leaking just below the carb there is a brass port an it is spitting from there an dripping from the the lowest intake bolts yes I did replace the upper crank seal also when it backfires it is a hard backfire I am sure it is do to the fuel the only thing I have not tried is to to run it from a gravity feed to make sure the pump is not over pressurizing this has thrown me for a loop lol I thought I was losing fire after it warmed up that is why I changed the coils I did not think it could be booth coils but figured it would be good to have booth new an the same oem but as I found that's not the trouble after you shut this thing off it drips raw fuel out of the exhaust as well it's like filling the crank as when I pulled the Intake there was raw fuel still blue with the 2 stroke oil lot's of gas lol Also the brass port that it is leaking from goes no where it has a small cut out in the block side but does not seem to go anywhere all I could figure is that enough raw fuel is laying there that it is just seeping threw

 

[eloham1979]

Re: 1972 18 hp Evinrude keeps flooding an backfires

it is leaking just below the carb there is a brass port an it is spitting from there an dripping from the the lowest intake bolts yes I did replace the upper crank seal also when it backfires it is a hard backfire I am sure it is do to the fuel the only thing I have not tried is to to run it from a gravity feed to make sure the pump is not over pressurizing this has thrown me for a loop lol I thought I was losing fire after it warmed up that is why I changed the coils I did not think it could be booth coils but figured it would be good to have booth new an the same oem but as I found that's not the trouble after you shut this thing off it drips raw fuel out of the exhaust as well it's like filling the crank as when I pulled the Intake there was raw fuel still blue with the 2 stroke oil lot's of gas lol Also the brass port that it is leaking from goes no where it has a small cut out in the block side but does not seem to go anywhere all I could figure is that enough raw fuel is laying there that it is just seeping threw

 

[Chinewalker]

Re: 1972 18 hp Evinrude keeps flooding an backfires

That nub should have a hose on it that runs to a similar nub on one of the intake port covers. It feeds unburned fuel from the intake manifold into the cylinder.

 

[eloham1979]

Re: 1972 18 hp Evinrude keeps flooding an backfires

so all this gas is normal as it is poring or spitting out that port an the other port is small as the lead on a pencil chain saw fuel line is to big for the one on the jug the one on the intake manifold is a 5/16 I think I was under the impression these ports where used for a pressurized fuel tank is there nothing that controls the fuel flow

 

[HighTrim]

Re: 1972 18 hp Evinrude keeps flooding an backfires

Pressurized tanks were stopped long before your motor was made.

 

[OptsyEagle]

Re: 1972 18 hp Evinrude keeps flooding an backfires

This would have nothing to do with the leak but might explain the backfire. How does the spark timing advance look? When you turn the throttle grip, is the mark on the throttle cam, in the center of the carbs roller, JUST as the throttle cam hits the carb's roller.

 

[eloham1979]

Re: 1972 18 hp Evinrude keeps flooding an backfires

I'm not sure I looked at the right piece but the roller on the carb that open the throttle is roughly contacting in the mag/stator plate in about the center of the roller maybe just a hair toward the upper side but center for the most part I just had it running on a gravity feed tank it does a lot less backfiring it only stumbles if you try a real low idle under throttle it hums right along still dripping fuel from the lowest intake bolts an I hooked that line back up that runs around a connects on the jug runs the it's gone back to putting a heavy black oil in my test tank which it dd when I first got it running but that had cleared up an it's back to smoking pretty heavy but I am sure with all that fuel in it it is all it can do also when I had the stator /mag plate off I did stake it out it was no real lose

 

[OptsyEagle]

Re: 1972 18 hp Evinrude keeps flooding an backfires

I would say your timing advance is OK. It would need to be pretty far off to cause a backfire. Are you sure you are not seeing a lean sneeze as opposed to a backfire.

Also, is your regular gas tank on the ground or raised up any? Some fuel pumps, as they get older, have a hard time drawing fuel up the 4 ft or so of elevation that can happen when in a test tank with the gas tank on the ground. In a boat the difference in elevation is usually less then a foot. In my tin boat I put mine on the 2nd seat to the left to offset my weight on the right, provided no one else is in that seat.
Anyway, if the gas tank was on the ground, put it on a table and see if it works better.

Don't worry about the crud in the test tank water. What you are describing is normal and all motors smoke a lot more in a test tank then they do on the water under load. They also drip more crud into the water, when idling in neutral then they do under load.

 

[eloham1979]

Re: 1972 18 hp Evinrude keeps flooding an backfires

I have also figured that the backfire has to be a lack of fuel or it sucking air I have adjusted the slow speed needle out an it helped it some but a few minutes later it was back to popping lol I wonder about the packing in that thing it has to be a problem in the carb as it is the delivery system I have new seals in there but it has to be sucking air just not sure where as I know the needle seat is holding it has to be bypassing an drawing threw somewhere is what I am thinking just a guess but I have not been able to pin point it when I pull the bowl it is super clean you could eat you oatmeal from it lol not that you would want to but it's clean I even adjusted the float up past the level area just to make sure it is shutting off an no dice

 

[eloham1979]

Re: 1972 18 hp Evinrude keeps flooding an backfires

the motor is still on boat fuel tank is in it's normal position the pump has new diaphragm in it when I have the motor in a 400 gallon rubbermade trash can lol it works lol I started the motor will it hooked to gravity feed the pump shot fuel out about 1 1/2 feet my other buddy has a 25 hp for a spare for his an said I can come grab the carb an see if that does the trick I will have to clean it but it's worth a shot it has just puzzled me lol

 

[racerone]

Re: 1972 18 hp Evinrude keeps flooding an backfires

Some times the needle for slow speed adjustment is turned but it does not move.----Turn it in and see if it seats.----Then turn it out 1-1/2 turns for initial start up.

 

[eloham1979]

Re: 1972 18 hp Evinrude keeps flooding an backfires

well it seem sto be running fine now not sure why but it has been over here purring along for close to a hr in the tank it is still dripping fuel it is actaually leaking from the brass fitting an hose on the intake an running down the hose just needs a clamp I turned the slow needle out until all the popping quit the oil in the tank has all but stopped now an it seems to be fine still not sure about this thing lol as it is still on gravity I did find some water in the tank on the boat I had put 3 gallons of fresh in it an there was not much left in there but I guess it had some water I should have checked it over better I put some in a mason jar an let it sit an there was plenty in there I think that has been a large part of it it still surges a little but even ran well in gear in the tank seems to be ok but I fixed nothing lol