94 DT30 Idle Problem

[Wahoo69]

I have a 94 DT 30. The engine starts, idles and runs good with the exception of a spot just at partial throttle where it runs but is rough. After the engine runs for several hours it will not idle and is hard to start. The primer bulb never seems to get hard but it is the same way when it starts and idles when cold. The carbs have been cleaned, new plugs, and non ethanol gas. Where should I start?

Thanks Dave

[g_craft]

first pull you plugs and see what they look like. if you don't notice any waterI would take it for a good run drive it wide open for a good jaunt then troll back to shore if you can. pull the plugs and see if they are milky or you notice water on them. My dt-55 had exact same problems my two bottom cylinders were filled with water due to a bad head gasket

Not saying that is your problem just something to check out

[g_craft]

also have you replaced the fuel filter?

[Wahoo69]

Thanks for the reply g_craft. I pulled the carbs and they did have crud in them. Cleaned them, adjusted the floats and reinstalled. Also cleaned the filter in the motor and replaced the Racor inline filter element. I took the boat out that afternoon and it did fine until we returned to the dock that night. I idled up to the dock and then cut the motor off while I brought the trailer down. When I went to start it again, it started and cut off and would not start again until it sat for about 10 minutes.
Around the time this problem started I had a leak at the temperature sensor on the head. It was cracked and and broke when I tried to remove it. I made a block off plate to cover the hole until I could order the sensor. I wonder if this could be causing a problem as the CDI uses the signal to change the timing when the engine is started. Pay day is coming and I will be replacing this so I will see.