New Owner-Carb Troubleshooting

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Hello all,
Recently bought a 1985 Nautique with a 351w.  Previous owner replaced spark plugs, fuel pump, converted to electronic ignition (Pertronix Ignitor I) and added a Holley carb.  

When I bought it, the engine would hesitate to start or require a lot of cranking.  Then, once started, engine would run great at high RPM and bog down, get surges of power, and quit once throttled back.  Boat was winterized and now will turn over, but not idle.  

I verified correct wiring of the ignition system, and correct ignition coil type, changed the oil, checked the spark plugs, and cleaned the carb.  

Just tried to start it up again this morning.  Engine would turn over, run for a second or two, and then fuel would start overflowing from the primary carb vent only.  After it was all said and done, there would be a lot of gas still coming out of the primary side of the carb into the barrels.  Vent tube overflowed on start attempts where the throttle was advanced and on attempts where the throttle was at idle the whole time.

I pulled the needle and seat assemblies, and found that the secondary assembly had pieces of worn o ring in there.  I cleaned it and resealed it. Primary assembly was good to go.

Questions:
Could the secondary fuel bowl cause the primary bowl to overfill and overflow?  
If all needles, seats, floats, etc are cleaned and working with proper fuel press, then what could cause an overflow?
What should my next step be to get this thing to run?

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MSPassDown Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: March-05-2025 Location: MS Status: Offline Points: 2	Post Options Post Reply Quote MSPassDown Report Post Thanks(0) Quote Reply Topic: New Owner-Carb Troubleshooting Posted: Yesterday at 3:01pm
	Hello all, Recently bought a 1985 Nautique with a 351w. Previous owner replaced spark plugs, fuel pump, converted to electronic ignition (Pertronix Ignitor I) and added a Holley carb. When I bought it, the engine would hesitate to start or require a lot of cranking. Then, once started, engine would run great at high RPM and bog down, get surges of power, and quit once throttled back. Boat was winterized and now will turn over, but not idle. I verified correct wiring of the ignition system, and correct ignition coil type, changed the oil, checked the spark plugs, and cleaned the carb. Just tried to start it up again this morning. Engine would turn over, run for a second or two, and then fuel would start overflowing from the primary carb vent only. After it was all said and done, there would be a lot of gas still coming out of the primary side of the carb into the barrels. Vent tube overflowed on start attempts where the throttle was advanced and on attempts where the throttle was at idle the whole time. I pulled the needle and seat assemblies, and found that the secondary assembly had pieces of worn o ring in there. I cleaned it and resealed it. Primary assembly was good to go. Questions: Could the secondary fuel bowl cause the primary bowl to overfill and overflow? If all needles, seats, floats, etc are cleaned and working with proper fuel press, then what could cause an overflow? What should my next step be to get this thing to run?

Jonny Quest Members Profile Send Private Message Find Members Posts Add to Buddy List Grand Poobah Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 3010	Post Options Post Reply Quote Jonny Quest Report Post Thanks(0) Quote Reply Posted: Yesterday at 3:48pm
	Tell us about the fuel pump. Have you checked the pump pressure with a pressure tester / gauge? If the pump is putting out greater than 6 or 6.5 psi, then the pressure can be too strong for the needle / seat / float assembly. The Holley 4160 carb is a good carb, but they can be very picky about fuel level in the float chamber. A good video to review can be found here: LINK. Was the Holley carb new or rebuilt? How long ago was the carb installed? It may be time for a carb rebuild / overhaul. JQ
	Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum

New Owner-Carb Troubleshooting

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