75 mercury carburetor jet sizes

[proutym]

I have a 1984 75 HP 4 cyl mercury outboard that I would like to confirm the jet sizes on. The Seloc book says the main is .090 and the vent is .072. On the actual carbs the bigger jet is on the vent and the smaller on the main. Could someone check either the mercury service manual or the clymer and see what it says.

Thank You

 

[Texasmark]

Re: 75 mercury carburetor jet sizes

What would it hurt if you swapped them and ran a test?

I am a total advocate of the fact that the lower engine(s) of a series are built identical to the hot dog excpept for the size of the jets. Makes manufacturing sense. Cheapest way to downsize an engine. $30 worth of jets and $50 worth of decals and you can go from the lowest (in a series) to the highest.

Mark

 

[Laddies]

Re: 75 mercury carburetor jet sizes

Well mark he could burn a pistion with a lean condition for starters! The Mercury Manual calls for .082 mains and .092 fot the 75 HP at sea level and .090 mains and .072 vents for the 80-85 HP

 

[Texasmark]

Re: 75 mercury carburetor jet sizes

Hear you laddies, but the rpm range is limited on the smaller hp because it can't get the fuel thru the small jets to run the higher rpm's.

I could be wrong. Don't have a manual on the old 4 cyl, but for the 3 cyls, the 75 and 90 not only have different jet sizes, but the carbs have different part numbers.

Ok maybe they change out the whole carb. This makes sense as it keeps the fuel air ratio constant then you wouldn't have the problem you mentioned.....too lean a mixture. But still, since everything is smaller, the WOT rpm's have to be lower which they are.

I yield to the power. :%

Mark

Mark

 

[jimmbo]

Re: 75 mercury carburetor jet sizes

My Factory manual shows 0.090 for the main jet and 0.072 for the vent