F4 YF Backfiring through carb

Sounds like something I bought at local boat dealer called Powertune I think by Mercury

 

I don't really understand and I have a F4 Hurricane which works well. At least.
I cannot give an advice too, sorry but I know that you are a good specialist so you'll find the solution.The explosion comes back from the engine, so the valve is open at a wrong moment.

I had a good result with my engine when I turned the "delco" to the right, it is the timing if I understand well.
I cleaned the filters of the carburetor before, the one for the accelerator pump was quite obstructed.

Maybe just changing the timing is enough. It takes time to check but easy to do.

It happend when an engine was very hot, on old cars. Maybe changing the quality of spark plugs, there was "hot spark plugs and others, I don't know all models but maybe it is good to check the spark plugs.

By the way I had one broken a little bit so it was wrong and with the new one engine is perfect.

I cannot help you and sorry for this, this engine is quite perfect, just change what is wrong, you are a specialist, maybe you have an electricity leak somewhere in high voltage, check also the wires... Soon it will be good!

 

It is leaning out in the accelerator circuit. Once up to speed it stops backfiring so just under rpm transition. Try choking it a bit to fatten it up and see it that helps. If it does then it definitely a lean accelerator circuit condition in the carb.

 

I agree that it is most likely leaning out in transition ----------- BUT, that alone will not ignite the fuel/air mixture in the manifold.

 

"It is leaning out in the accelerator circuit. Once up to speed it stops backfiring so just under rpm transition."
I would tend to think the same... but also I've had that condition with ignition troubles, such as dirty points or bad timing.

I would suggest doing the easy stuff first, like the vacuum check... or retarding the timing a couple of degrees, just to see if that helps.

 

But Howard, I did tell you that about 15 posts ago..........just a slightly different terminology.

 

New at this, Howard?

R)

 

Well now I feel a little better about misreading the spark plug gap and setting my plugs to the point gap specs.

 

I would not have thought it would run that well firing 1-2-4-3 vise 1-3-4-2! Info shows some V-W's did rotate clockwise with 1-2-4-3 but that's not an F-head. Glad you didn't tear down your new engine though.