Cas42:
A vacuum leak is never good, but I don't know how to express it in terms of fuel consumption. The jetting, however, sounds lean to me. I'm not a carb expert, but there are some good carb guys here. By comparison, my Marine Power 454 came stock with a 750 vac sendonary Holley, and 86 jets, front and rear. You may be able to get more rpm's simply by changing jets to some larger units.
Steve.
Cas , when you have a vacuum leak the idle gets rough.The tube on the carb you mentioned should be the vacuum gauge hook up, and the big tube for PCV hookup.Consumption will be high at high RPM regardless of your jetting.Rule of thumb,if you can keep your jetboat on plane between 2800-3000RPM that's where your best economy will be.6-7 GPH at 3000, 20-24GPH at wide open!The 780 Holleys work best with 72 primary, 86 secondary.And yes, go for 6.5 or 4.5 power valves.As I mentioned in previous posts, the best result I got from a Holley 830 vacuum secondary marine carb for a big block.
[This message has been edited by spectras only (edited April 17, 2001).]
Posting Permissions
Reply With Quote