1989 90hp idle and starting problem

- I replaced old gas with new gas.
It try to start but didtn't idle.

- I cleaned carbs, fuel pump, fuel filter.
It starts and idles and doesn't stall on muff. I put it in forward and prop rotates fine.

- when in water
It idles for about 20~30sec then stalls but it runs okay if I move the lever to forward just before it stalls. I need to try several time to get it moving.
voltage reads 12.8v when it idle.

Another thing I found was if I move the lever to WOT(forward all the way) then bring it back to neutral before start the key. It starts stronger and creates lots of white smoke and idles a lot better. It will let me put in forward gear easier. Is it a bad thing to do?

carb sync problem? throttle cable adjustment?
what effect do I get from adjusting idle mixture screw on each carb?
I don't have tachometer so I can't figure exact rpm.
clockwise - rpm up?
counterclockwise - rpm down?

Re: 1989 90hp idle and starting problem

The idle needs to be around 800rpm on w/ muffs. I have a 1984 115hp i-6 and had that problem, I increased the idle just a bit and it helped. I've been told by others that these engines are not the easiest to get going. I don't have an idle lever (boat is newer than engine) so I press the button that disengages the shift linkage an advance the throttle arm about 1 inch. This give is just a bit more juice to get the ?tower of power? cranking. Seems to work great for me.