alcor

Now that ther running right, what should the top rpm be. There totally rebuild 1984 454's with solid lift cam's and lifters, crane roller rockers, .030's over on cylinders and supposedly right at 500 hp with 750 dual pump Holly's, 425 TRS outdrives and c71 counter rotating BW transmissions. Props are currently 15.5", 4 bladed SS 22 degree Intimidator. The engines are currently maxing out at 4300 rpm and appears to be running about 65 mph (gps). Boat's a 36' 1984 early Sonic (coyote) believed to be in the 8,500 to 9,000 lb range.

Of course I want to go faster.

1. What RPM can I safely shoot for?
2. What speed range can I expect?
3. What prop should I be running or can these be re-pitched to the right angle?

All input will be appreciated as I haven't a clue where to start.

Al

Griff

You need to run at least 5000 rpms, especially with solid lifters. Solids are made to run at higher rpms and that is the only reason to have them. You are probably not even into the power band of the engine at 4300.
Maybe try some 21" Mirage+'s or even 19"s.

PatriYacht

Check your tach and speedo. According to Bam's prop slip calculator (www.go-fast.com) at 0 slip, your speed at 4300 rpm is 59.7mph. With normal slip in a heavy deep v, you're really running low to mid 50's. If that is gps speed, your tachs are wrong or those props aren't 22 pitch. TRS gears are 1.5 to 1.

blue thunder

If the gps is correct, and the prop is a 22", your rpm would be 5400 with 13% slip. 13% slip is generous, so you may be spinning the engine even a little higher. I'd say if you have forged rotating assemblies and rectangle port heads, that engine is tuned well. You may try going to say a 25 mirage which would bring you down to say 5000rpm, but may give you more bow lift and therefore top speed. This is all based on the tach being off, not the speed. If the tach is reading correctly at 4300rpm, well then never mind

BT

HOUSTONPROP

AT 4,300 IT'S too low,If the tach is correct which I assume it is ,we then could pitch the props to a 20 pitch which will increase the rpm 300 lab the props for 200 rpm and reduce the dia 1/4" which will pickup another 200 rpm,this will put the rpm at 5.000 rpm just at the top of the rpm band.Darin
Just a thought?