Go-No Go Mercury 3.5 Help please

[sparrowhawk1]

Originally Posted by Nicholson58

As I noted, the fuel line delamination was on an antique merc. No fuel pump and the tank was around the flywheel above the carb. A bad fuel hose will do this.

If you read my earlier post I told the O P if changing fuel didn't solve the problem to unscrew the drain on the carb and see if fuel flows freely.
From the symptoms and the fact that he's changed the carburetor I'm going with the reed valve. Or as stated above a vacuum leak in the crankcase and I hope he is told what the problem was and he lets us know

[MBWhite]

As A64 mentions, at this point we do not know if it is even a 4 stroke or a 2 stroke motor, so any guesses are completely that.


When we know a model number and an age then we can begin the stabbing in the dark in earnest!

About the only universal troubleshooting I can suggest for both motor types is to use an ignition timing light on the spark plug lead while running and just look at the flashing it does. It will be rhythmic but if a sputtering under power is caused by ignition the change in the pattern of the timing light is quite obvious.

You can narrow down fuel issues by giving the engine a couple whiffs of starting fluid when it is struggling. If it blazes to life then you can start inspecting the fuel delivery system. If it is a 2 stroke you can also give short puffs to isolate vacuum leaks, especially crankcase seal issues.

In the meanwhile, all we can really do is wait patiently for some engine information.

[shantycrew]

This engine is a 4 stroke Mercury 3.5 HP which was bought new less than 2 years ago. I don't have the serial number to hand whilst writing this. Yesterday I had one last go at cleaning the carb. When I tried starting it it fired up but I suddenly noticed I'd forgotten to replace a rubber pipe that connects to the top of the air intake filter. What seemed strange to me was that there was some kind of liquid, discoloured, coming out of this tube. Not sure if it was water or fuel, or a mixture as I shut down the engine immediately and didn't taste it or get a sample.
What is this tube for and should it have gas or water coming out of it, looked like it was under pressure as it squirted out which alerted me to the fact that I had forgotten to re-attach it.
By then the twilight was descending fast so I left it until today and will try to find out what this pipe should be doing.