Join Date: Mar 2007
Location: New England
Thanked 7 Times in 7 Posts
Rep Power: 10
Sounds like two different problems
Black exhaust could be soot as SD mentions. If you want to to determine if this is the culprit for the black water exhaust, disconnect the exhaust hose from the muffler and put your finger in it and see if the water in the muffler is black and see if the exhuast hose has any build up in it. If the exhaust water is black, disconnect the exhaust hose from the motor to the muffler to see if that is full of exhaust soot. If so, replace.
The sluggishness on idle/throttle could be related to the black water, but if you have good flow of water out the back, it probably isn't because a significant build up of of soot in the hoses, would result in reduced water flow and water backing up into the motor.
If you haven't changed the fuel filters since you have owned the boat, this could be the cause. A fuel tank that is 1/2 full or less isn't the cause. Do you have a water separator? If so, does it have a clear bulb on the bottom? What color is the fuel in it? If it isn't clear/pale yellow, that could be an indicator of dirty fuel. Changing both the primary and seconday fuel filters could make the difficult starting and the sluggish starting a thing of the past.