1968 40HP Evinrude Big Twin electric start carb problem

[andreipou]

Hello,
My engine started to run gasoline from carburator , like it is overflooding, so I dissasembled carb and put new float, needle with seat, gasket.

Now when I try to start I have to open throttle as much as I can on neutral to get it started and it starts , runs for 2-5 secs and stops. Then again starts , runs and stops.
I can see fuel in glass filter coming up.

ANy ideas?

Thanks.

 

[F_R]

Slow speed needle set too rich or lean?? Too much choke?? Hole in choke heat exchanger?? Did you mess with the throttle roller?

 

[andreipou]

Slow speed needle was not touched since it worked last time, but I tried to play with it and it did not help.


I tried choke on or off and when on it does not start at all.


Not sure how to check heat exchanger. It is a 1/4 pipe from carb to head that I have to remove each time I remove carb, right?


When I removed carb I tried not to touch anything else, because everything was rebuilt and tuned up only a few months ago and ran great before flooding.

 

[F_R]

So, won't start with choke on? Even when cold startup? If that is a true statement. that sounds like it is way too rich.

There are two holes in the heat exchanger, one for the pipe and below that, another for air inlet. You should not be able to blow into one with the other blocked. You can also simply remove the pipe for test purposes. Of course if you do that, the automatic choke won't work and you will have to manually choke it.

 

[andreipou]

While replacing spark plugs the thread on tip cyl came off :facepalm::facepalm::facepalm::facepalm::facepalm:.
Now have to put thread insert before I do anything else....

This engine keeps me buisy

 

[racerone]

These engines are very simple and also very reliable.----Bonus is that you can do most of the work yourself.-----Makes for economical boating.---Do not give up on it.----Does spark jump a gap of 1/4" or more, yes or no ?

 

[andreipou]

Spark is J4C.
I think I did inserts on my 25HP 1972 Johnson for the same plug years ago and have the tools and inserts. I need to find it.

 

[racerone]

Does the spark jump a gap of 1/4" or more, yes or no ?--A very important question for you to answer.

 

[andreipou]

Not sure what jump gap is, but insert is M14x1.25 SHORT.
I found the kit and extra inserts and already put it in.
Now have to wait 24 hours for thread sealant.

Why is it important?

 

[F_R]

If you hold the wire 1/4" away from the head, a spark should jump the gap when you crank it over. It is important because it is a diagnostic clue. We need input if we are to guess what's wrong with your motor.

 

[andreipou]

I think I recall now what you mean.
My 25HP Johnsons manual (it uses the same plugs) says that for spark plug checker gap has to be 7/16.''.

I think that is what you refer to.

But original manual for this 40HP Evinrude does not have this info. I remember looking for it when I started to work on this motor.
Therefore, I always use actual plug grounded to motor to see if spark is strong or not.
Maybe you can tell me what it should be.
Model is 40853D.

BTW, I put new coils and whole ignition system on it last fall.

P.S. The engine was completely re-build last fall and already used a few times this year and ran great until the overflooding.
So, ignition problem is not very likely.
I wonder what I messed up when rebuilt the carb...

 

[racerone]

????----1/4" or more has been mentioned several times here.

 

[andreipou]

SO, what you are saying : I need to set spark checker gap to 1/4'' and see if sparks, right?

I can do it tomorrow when sealant dries up.

 

[F_R]

Motors with Mag CD ignition are checked at 7/16". You don't have Mag CD. The gap in a spark plug is only .030", about 1/32", a far cry from 1/4" and nearly useless as a spark check.

You wrote, "P.S. The engine was completely re-build last fall and already used a few times this year and ran great until the overflooding.
So, ignition problem is not very likely." It is that kind of thinking that causes a lot of wasted time and money "fixing" the wrong thing.

 

[andreipou]

so, it is not clear what you are telling me to do....

 

[andreipou]

I set gap on spark tester to 1/4'' and got sparks.
I put new spark plugs.
I dissassemle carb and blew all holes with compressed air.
Adjusted throtle again.
It starts with both choke on or off now, runs a few secs and shuts off.
I tried to play with low speed needle and it did not help.

What can it be?

I made short videos to upload, but looks like MP4 files are not allowed.
Maybe I can send them to you guys and you see and get better idea...
I am stuck.

 

[andreipou]

Anyone?...

 

[Tim Frank]

The ignition test was quick and easy and rules out that as a trouble source.
You need to cycle through spark, compression and fuel.

Check compression; if it's OK, you likely have a fuel issue.
The sticking float needle that caused the gas overflow suggests garbage/debris in the fuel. That means a more rigorous carb cleaning. Be sure tyo remove Welch plug as well and clean behind it.

 

[andreipou]

So far I never removed Welch plugs on all carbs that I cleaned and it worked fine.
I am a little itimidated to do that because of some stories on how it really messes up the carb.

I guess I should do it now for the first time and learn (after retesting compression that was 120/120 last summer BTW).

Is there anything I should be specifically aware when I do that?

 

[Tim Frank]

How have you determined that compression is OK?