K&B 3.5 serious problems running in the water

[aod8858]

I have an old 3.5 outboard and i have been having problems with it running out of water and when its in the water it runs good for about 25 yards and then sputters and dies. I have used the factory settings on the carb and went back and forth with minor adjustments about 2 full turns both ways and nothing changed. I am thinking that the problem is water down the carb becaus I put an air filter on it and it finally made one good run for about 40 seconds and then died. When I got it back to shore, the carb had water in it and the filter was soaked. If you think that this is the problem, could it be trim angle or how far up and down the motor is mounted on the transom? The boat is a Dumas hot shot, so nothing strange about this set up. Is this a problem that is common? I know of lots of people that are running this combo with no problems.
By the way, I race nitro buggies and trucks every weekend and have been around nitro engines for years so all the basic problems that could cause this have been checked out and everything is fine. Any info on this problem would be very helpful to me.

[MECOA]

first read this

http://www.mecoa.com/faq/carb/needle_marine.htm

then tell us what happens

You don't need an airfilter on water and the reason it helped is because it made the misture richer. Please read the above link.