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1989 3.0 rough idle

C

cnort8

New member
"1989 sea ray 160br 3.0 mercruiser. Problem: after running under heavy load (2/3 throttle or more) for 10 min. or so when I throttle down to idle the motor runs rough. It sometimes wont get back up on plane unless i puttz around for about 5 or 10 min.. It will rev up and smooth out at 1000 rpm but lacks something to get on plane. About 2200 rpm sort of bogs. I have corrected numerous other problems in the 1 year that I have owned this boat but this one has me stumped. timing is @6deg btdc. comp is 125 to 135. New fuel pump and filters(filters twice just to be sure). New points, plugs, wires, cap, rotor and coil. All mercruiser parts. Temp guage stays around 155 though I know enough not to trust it completely. When this condition occurs I can put my hand on the u shaped part of the exhaust snd it doest feel any different than at any other time. Could carb be heating up and if so any cures. Ask questions and I will answer what I know. Its still cold here in Illinois but I will be working on it soon. thank you."
 
"Just a few thoughts that pop

"Just a few thoughts that pop in my head:

check the choke for proper operation

clean n rebuild carb

is the timing advancing properly

vacum leak when it heats up, something expands"
 
"You cleaned the filter in the

"You cleaned the filter in the fitting that enters the carb?

You have a fuel water separeter, dump it in a clear jar and let sit, is here water on the bottom?

You pull the anti-syphin valve and fuel pickup tube, the screen clean on the tube, the valve clear working good?

There a filter in the fuel pump?

The vent is clear?

All above good, timing good? Spray some carb cleaner at the base of the carb while running on the water, it run different then the carb may be loose on the mani. Maybe the carb does need a rebuild.

What do the plugs look like?

Run the boat in pitch black, at night or in a garage, look at the motor what do you see?

Ok run it on a external tank of gas let us know the result."
 
"I have tested most of these a

"I have tested most of these already except carb rebuild. These are all good suggestions and all three responses refer to carb, so rebuild it is! I appreciate the info. I will let you know the outcome. thank you!"
 
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