Crazy carburetor issue 1985 Force 125hp

Went out on the river with a friend to adjust the idle on my 125hp Force outboard (1258x5a). The engine runs (what I would consider) very good with the needles out 2.5 turns. When I turn them there doesn't seem to be much difference in sound. 50:1 fuel mixture. At idle (850 rpm or so) when I slip it into forward, idle drops to 550 or so. However, if the cowling is on, engine will stall. With cowling off, engine will never stall. With GPS, 37 mph top speed (18 1/2' Bayliner Capri) with cowling off and 34 with cowling on. Not enough air? I adjusted and sync'd carbs and they are as close to horizontal as I can judge. I can raise idle higher than 850 (each rotation of the linkage arm gives me approximately 150 more rpm but is that a good idea. For whatever reason, I can only pull away from the dock without killing the engine 20% of the time with the cowling on. Kind of dangerous and loud and hillbilly without it.
What am I doing wrong.

Re: Crazy carburetion issue 1985 Force 125hp

Re: Crazy carburetion issue 1985 Force 125hp

A LOT!

First, idle speed is too low. It will stall almost every time at 850 in neutral. It should be 700-750 in forward gear, in the water. This is usually somewhere around 1000 in neutral but varies with the pitch of the prop used, so the Forward gear setting is the one to use.

Idle speed is not set with the carb link or timing link. It is set with the stop screw on the timing tower at the cast arm. Go to the FAQs and reread the sticky on synchronizing timing and carbs. Be certain that the timing is set correctly at 30 degrees before top dead center at wide open throttle.

If the low speed needles are that far out, look for partial clogs in the carbs, damaged low speed needles, improper float level, or damaged inlet needles. A correctly set engine with good compression and carbs should idle quite nicely at about one turn out.

Stalling with the cover on is usually due to exhaust leakage. This will also affect top speed as the engine is not getting a full charge of fresh air. The most likely place is the bellows at the rear shroud. It should be complete and not damaged AND should be properly seated in the rear shroud.

Re: Crazy carburetion issue 1985 Force 125hp

Re: Crazy carburetion issue 1985 Force 125hp

Frank,
Is what you call the "bellows at the rear shroud" . . . on the exploded parts diagram called the "boot idle exhaust"?

Re: Crazy carburetion issue 1985 Force 125hp

Re: Crazy carburetion issue 1985 Force 125hp

Yes. It is spring loaded with an internal plastic ring at the tapered end. Sometimes the plastic ring will melt so check that too.

Re: Crazy carburetion issue 1985 Force 125hp

Re: Crazy carburetion issue 1985 Force 125hp

Thanks!

Re: Crazy carburetion issue 1985 Force 125hp

Re: Crazy carburetion issue 1985 Force 125hp

Took the motor leg apart, boot looks fine, spring fine. Missing the insert. What is the purpose of the insert? Is it necessary, I haven't checked availability yet. I have a portable digital tach, I painted the edge of the flywheel black and attach a reflective sticker on it. At WOT, with cover off last night I was getting 4800 rpm, my understanding is it should be running approximately 5500rpm. Correct? Thanks again!