Optimum WOT?

[Raisin Wake]

Anybody know the optimum WOT rpm's for a 7.4 liter Mercruiser V-8?
Thanks

[RiverOtter]

Anybody know the optimum WOT rpm's for a 7.4 liter Mercruiser V-8?
Thanks
Back when I had one seems like it was 4,700 or so.

[TCHB]

If it is the small horsepower engine it is 4800 max.

[Raisin Wake]

I think the horsepower is around 330????

[phebus]

Here you go, 4200-4600.
MerCruiser 7.4L MPI Specifications
Propshaft Horsepower: 310 (232 kW)
Displacement (Liter/CID): 7.4L/454
Cylinders: V-8
Bore & Stroke (inches/mm): 4.25 x 4.00/108 x 101
Compression Ratio: 8.9:1
Fuel System: MPI
Full Throttle RPM Range: 4200-4600
Ignition Type: MEFI/EST Digital
Alternator: 65/917
Length (inches/cm): 39/99
Width (inches/cm): 32/82
Height (inches/cm): 24/61
Weight (lbs./kg) - Alpha: N/A
Weight (lbs./kg) - Bravo One: 1158/525
Weight (lbs./kg) - Bravo Two: 1170/531
Weight (lbs./kg) - Bravo Three: 1179/535
Weight (lbs./kg) - Blackhawk: N/A
Gear Ratio - Alpha Drive (primary/optional/high altitude): N/A
Gear Ratio - Bravo One (primary/optional/high altitude): 1.5/1.36/1.65
Gear Ratio - Bravo Two (primary/optional/high altitude): 2.0/1.81/2.2
Gear Ratio - Bravo Three (primary/optional/high altitude): 2.0/1.81/2.2
Gear Ratio - Blackhawk (primary/optional/high altitude): N/A

[MOBrien]

I've got the 7.4MPI (310hp) in my 24' open bow Cheetah turning a stainless 21P 4-blade "Revolution" and get 4650 trimmed up at about 61mph.
What kind of boat is it???
Hope that helps.
-MOB

[Raisin Wake]

22' Eliminator Extreme. Right now I am trying to prop it correctly. I'm running a 21 pitch 3 blade SS mirage. My WOT rpm was right around 4700. Although it was a little rough when I tested it. I want to move to a 4 or 5 blade prop, because I'm having cavitation issues at throttle up. I was looking at the 5 blade 23' prop. Will my rpm's be too low?

[Raisin Wake]

I've got the 7.4MPI (310hp) in my 24' open bow Cheetah turning a stainless 21P 4-blade "Revolution" and get 4650 trimmed up at about 61mph.
What kind of boat is it???
Hope that helps.
-MOB
Does a 4 or 5 blade prop of the same pitch, produce the same rpms as a 3 blade prop of the same picth?

[phebus]

Lots of variables (i.e. diameter, cup, design, etc.), but the general rule of thumb is to drop 1" in pitch when going from a three blade prop to a four blade prop.

[Raisin Wake]

I just got an email from a prop shop. They said I might want to consider a 4 blade prop. What are the downfalls of a 5 blade prop? I'm not as concerned about my top-end as I am about my pulling power and ability to plane quickly. I still ski and my kids just learned how to ski.