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It can be very bad for the engine to use starting fluid as it is very volatile and also removes the lubricating oil from the cylinders. If you use a small squirt bottle with mixed gas it will still serve as a testing tool but is better for your engine.
Now, on with your problem. Did this problem start suddenly while in use or did it happen after the engine was in storage for the offseason?
Please let me know that info and anything else you can think of and I will try to direct you to the problem.
Ok, the fact that you have fuel getting to the carburetor and flowing out the drain is good. But quite often, even after cleaning, the jets and passages that actually deliver the fuel to the venturi can remain blocked with what we call "varnish". When untreated fuel evaporates in storage it leaves this gummy residue.
Remember that the high and low speed passages in the carb a very small. The high speed jet is also located right in the bottom of the float bowl where all of the contaminants will eventually end up.
I suggest you locate the high speed jet, remove it, and examine it very closely to make sure it is not restricted. Be careful if you have to use any picks or hard tools to unblock the passage that you don't damage the size or shape of the opening as even small changes can affect engine performance.
Good luck and let me know if this does not solve your problem.
In my terminology, the main nozzle is the pipe which lifts the fuel and delivers it right into the throat of the carb. The main jet is mounted at the bottom of the nozzle, or quite often in the float bowl itself. Access to it is possibly through the bowl drain screw. The passage way on a main jet will be in the .020 - .030" range. Try to visualize the path that fuel will have to take to get from the fuel bowl to the nozzle in the venturi. The jet is the first thing that fuel will have to pass through.
Hope this helps, Matt
Lets try a test.
Make up a small plastic bottle that you can fill with gas. It has to be something with a squirt lid or a small hole that you can meter small amounts of fuel. If you clean out a small pop bottle an then drill a 1/16" hole in the lid that would work good.
If you use this, and experiment a little bit with the amount of fuel you are putting in, you should actually be able to keep the engine running as long as you keep adding fuel.
If this is the case, and the carb float bowl has fuel in it, then there has to be blockages in the carb still.
Please let me know what happens with this test.
If the carburetor is overflowing when you squeeze the primer bulb, then the needle and seat in the carb is not working correctly. All of what you descibe points to fuel that has gone bad in storage - there are products to add to the fuel in the fall that will prevent this from happening again.
As for float level, if you haven't changed it, it won't have changed while in storage. The carb needs to come apart again, thorough cleaning, and have a kit put into it because the needle and seat are either stuck open or not sealing from what you describe. The float level should then be checked anyway when you replace these components.
BC Boat Guy Matt
On parts that are related to the fuel system, I wouldn't recommend making anything to get by. The potential for leaks and fire hazard just isn't worth it.
Hopefully you are on the water soon. Nice talking to you and good luck.
Glad I could be helpful to you.
Happy Boating. Matt
How did you adjust the pilot screw after rebuilding the carb? Is the idle speed just too low? When the engine is in the water, it requires more fuel to idle than when it is in the garage.
I have opted out of your question to allow other experts to perhaps provide you with additional information.
If no one repsonds, then I will continue to try to help you.