Ok heres the scoop. I have an 85 Mercruiser 260 with a thunderbolt IV ignition. I have just replace the carb from Guarunteed Carburators(rebuilt). The problem is the old carb surged at idle speeds. The Rpms go from 800 to 600 randomly. I had issues with the old carb idle screws being stripped so I thought a new rebuilt carb would fix a possible vaccuum leak in the carb. I hook a vacuum gauge and get crazy readings at low rpm and great reading at high rpm. High RPM engine runs like a top. The guy I bought the boat from rebuit the carb and put the wrong gasket on the base to intake. So when I got the new rebuilt carb I ordered a base gasket. This gasket covers up alot of the ports on the carb when I hold it up to it. It also covers stuff up on my intake. I still have surging problems. My dad has a twin engine boat with the same year engines and carbs. He says his gaskets are thick. My gasets are thin. I don't know if I am fighting a gasket problem or some other promblem....here is a list of questions I would like some input on:
- Thick and thin gaskets? Do they make a difference at idle?
- Where can I find out 100% which gasket I need, I have seen 4 versions
- Could I be chasing and grounding issue on the ignition?
- Would slight corrotion in the distributer housing effect spark at low rpm. (cap & rotor are new)
- Possible air leak pre fuel pump sucking air causing low pressure?
- How do I install a fuel pressure gauge with prebent solid fuel lines
Please help I troll for salmon and spend 90% of my time at idle speeds and this surging is annoying.
- Thick and thin gaskets? Do they make a difference at idle?
- Where can I find out 100% which gasket I need, I have seen 4 versions
- Could I be chasing and grounding issue on the ignition?
- Would slight corrotion in the distributer housing effect spark at low rpm. (cap & rotor are new)
- Possible air leak pre fuel pump sucking air causing low pressure?
- How do I install a fuel pressure gauge with prebent solid fuel lines
Please help I troll for salmon and spend 90% of my time at idle speeds and this surging is annoying.