84 115 mid range jet removal???

[neilthewheel]

Saw earlier post about removing this particular jets on carbs. Something about mid rang jet. Author said to remove it and throw over shoulder.

 

[Chris1956]

Re: 84 115 mid range jet removal???

A '84 115 Merc will have sidebowl carbs. There is no midrange jet. You may be thinking of backdraft jet. There is a lot of discussion about disabling backdraft feature. I never had an issue with it.

 

[neilthewheel]

Re: 84 115 mid range jet removal???

Ahhhhh. Getting ready to freshin them up. Didn't like the idea of leaning it out.
Thanks!

 

[neilthewheel]

Re: 84 115 mid range jet removal???

A '84 115 Merc will have sidebowl carbs. There is no midrange jet. You may be thinking of backdraft jet. There is a lot of discussion about disabling backdraft feature. I never had an issue with it.[/QU

Found it. This make any sense?

On the float bowl cover is a small brass air jet. Pull it out, unscrew it, and junk it. It is a midrange air jet that leans the mixture out a midrange to give better fuel millage at cruise. But what it ends up doing is leaning the engine at the same time the timing is most advanced, and detonating the engine. Next check your idle mixture setting. I recommend two turns out from lightly seated for an initial setting. This gives you enough fuel to get on plane easily. While in the water once the engine is running correctly turn this mixture in about 1/8 turn, accelerate to get on plane. If it does easily try turning in another 1/8 turn. Do this to get the best idle and to ensure the boat gets on plane easily. Do all three carbs at the same time.

 

[Chris1956]

Re: 84 115 mid range jet removal???

That is the backdraft jet. There are some who want to junk it. I never had an issue with it. Just so you know, the carb bowl is connected to the venturi, thru that small hose. As speed increases, air flow increases in the venturi, pulling more air thru the carb bowl, due to Bernouli's principle. At some point the draw of air from the bowl will be restricted by the backdraft jet. This causes a slight vacuum in the carb bowl leaning the mixture a bit.

It is not as dramatic as the post you found. Nothing about "detonating your engine".....