I have a 1958 Hiawatha 7.5 outboard. The model is OM3-7989B. This one is a bit different than the 7987 model in that the carb adjustments are on the inside. There is a big knob that is the high speed and a small one on the bottom that is idle. I turned the high speed out 1.4 turns and then back into 3/4. Now it will run as long as the choke is engaged. This shouldn't be. I have an airline that runs from the bottom intake under and over to a tube on the bottom of the carb. If I take this off the engine runs. Put it back on and try to slow the speed and it dies off. It's not smoking due to cutting back on the oil a bit. I have run a can of Seafoam down the carb slowly. This is the first time the engine has run in 28 years. That line I am talking about spits out air, so I know it's not plugged up. The needles are clean and silver. There is no bowl or glass bowl on this model and getting the bottom of the carb requires some magic! It is so tight in there. Any ideas would be welcomed. I thought perhaps there was suppose to be a baffle or diaphragm on the intake, but the book I have or the sister to this one doesn't indicate one, however it does talk about a gasket. New plugs, a couple of lines replaced. Condensor and points all cleaned up. I do believe the manual said the fast or high speed is factory set. I have it opened right now a little over 3/4. The small one is opened 1/2 from a closed position. A side note, I have a lot of gunk come out the exhaust and I am running non-ethanol gas in it.
