Motor starts good, cylinders 1 and 3 strong spark but no fire at idle until rpm is up to 3300 or more under load or not. At higher rpm under load pulled plug wire and definitely is firing as it made motor slow down. The spark is constant strong all speeds,carbs rebuilt but were clean anyway.compression good, new fuel ,bleeder hoses good, In the water tied to dock I warm up motor put in gear you can tell it is not all 6.I then add throttle motor bogs down ,sneezes once put does go up in rpm even on 4.I pull off the plug wires one at a time and always 1 and 3 are not making a difference. Then as the throttle is pushed down and rpm builds they kick in and the motor sounds good. We untie from the dock do the same and if we can get the rpm s up by fluttering the throttle the cylinders will kick in and the motor will run good as long as you keep the speed up .It will top out at 5,600 rpm. I was given this motor so I do not know if it ever ran good at low speeds.It has been in storage a couple years.I put new switch boxes on it as I had them but no difference.Could it be the the carbs and would spraying a little gas in the carb throats while under load to see if any change help. Also on this engine are the port carbs for the starboard cylinders. I heard the 175 is different from the 200 carb to cylinder set up. Serial # OB 128324. I thank you for any help
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