I wanted to revive this thread from 2015 because the ideas have been incredibly helpful, and because I am hoping midskier or someone else can solve my problem. I've done everything suggested in this thread so far, plus a whole lot more. In spite of that, my max speed is 32 mph and max engine rpm is 3400.
Boat: 1990 Volante with Indmar/Ford 351 engine - lake is at 5000' elevation.
Data Collected:
- Idle set to ~750 rpm unloaded; ~650 rmp in gear
- Idle mixture adjusted for max rpm
- Idle timing set to 8 degrees BTDC
- Full throttle speed ~3200-3400 rmp - boat speed ~32-34 mph GPS measured - very light boat with just the driver, ~1/3 tank of fuel, and little to no gear
- Secondaries start to kick in ~2400 rpm - close to fully open by 3200 rpm
- Max timing advance ~30 degrees BTDC at ~3000 rpm
Parts changed so far:
- 80319 Holly Carb rebuilt by National Carbs - rebuilt again by me last month
- Acme 13x11.5 Prop (similar results with the original 13x12 Acme prop)
- Pertronix Flame Thrower II distributor
- Flame Thrower Ignition Coil
- MAGFORCE Marine spark plug wire set
- NGK V-Power Spark Plug (UR4) x8
- Sierra International Fuel Water Separating Filter
- Edelbrock inline FUEL FILTER ELEMENT
- Oil/Filter
- Various secondary diaphragm springs tried - currently using 'purple'
Based on the posts in this thread, it seems I should be able to expect a top speed closer to 42 mph and a top engine RPM of ~4200. Is this a realistic expectation? At 5000'? What else should I be looking at?
Thank you all for your help.
Rick