Mercury intake tunnels???

[tyst67]

57525 what are these tunnels for in the intake and what would happen if I plugged them?

[OUTBOARDER]

help balance intake pulses at low rpms so it trolls around and gets on plane

[tyst67]

help balance intake pulses at low rpms so it trolls around and gets on plane

So this is why my motor bogs at low idle when in gear

[OUTBOARDER]

no , needs to be tuned up

[fs5]

I always thought it was for priming fuel to start it

[sabine river killer]

on some engines is a good mod to make these larger or to add them when their are none but you can ruin a good intake at the same time

[OUTBOARDER]

on some engines is a good mod to make these larger or to add them when their are none but you can ruin a good intake at the same time

In general larger the dia or area higher effective rpms. several
snowmobile triples have them to help low rpms out.

[Fastjeff57]

So do some twins. This is a Yamaha set up.

Jeff

[tyst67]

So do some twins. This is a Yamaha set up.

Jeff

So they help with low end rpms and wide open rpms?

[sabine river killer]

you are actually pulling from all the carbs. on a 2 cyl 1 carb set up it helps to cut a window in the intake to do this. the big briggs twins like it

[Fastjeff57]

Here we go again; speculation: My best guess is that they are to improve idle by reducing standing wave action.

With one carb per cylinder, there's a standing wave of fuel droplets in front of the carb at certain rpms--it's a length/ rpm tuning thing. (That's one of the functions of those "silencer" air boxes attached to the carbs; to contain this.) If you've seen that standing wave of fuel hanging in mid-air it's kinda scary; I mean, one good spark and....ka-boom!

My late and much mussed buddy Clint watched a big block Chevy running on a dyno with Hilborn injectors. There was a MASSIVE cloud of fuel droplets 18 inches high above each of the 8 injector pipes at certain rpms!

Jeff

[OUTBOARDER]

45ss does it getting on plane. will try balancing tubes soon.

[Fastjeff57]

Here's another factory intake set up, this one from a Merc 90 triple. Note how deep those inter-cylinder passages are!

Jeff

[fs5]

I removed the attentuator from my merc triple and every time I pull the cowl to wash it when I get home there a lot of fuel sitting in the lower cowling.
I was thinking about making up some venturi's for it ,do you reckon this would help?
other wise I was going to refit the attenuator back on.

[Fastjeff57]

That's the standing wave of fuel droplets impacting on the cowl and settling.

Jeff