need higher rpm range on chrysler 318

[LEASEGUY]

anyone have any after market solutions to increase max by 2000

[stonebreaker]

Where would that put your redline?

[Jango]

First of All,reliability would suffer, unless 6000 - 6500 was only an occasional Burst.

If you're willing to go to a smaller prop, very little need be changed. Perhaps, nothing.

If you're looking at a 2000 RPM increase with a 40% to 50% increase in speed, HP will need to be More than DOUBLED.

Required HP increases expodentially with speed. This would require a TOTAL rebuild of motor - Higher compression, stronger crank, Rods, Higher flowing Heads, complete valve train change, cam , carburation etc. Not exactly an Inexpensive operation.
Less expensive to go to a larger motor.

[LEASEGUY]

Any thoughts on rebuiding small bloch to 350-375hp so I have more tourque and losing the 2:1 reduction?. I'm thinking this would double my prop turns without the need for 5-6000 rpms. I would be happy if I could spin this four blade @ 3000 rpm, which means docking at idle im still turning 750 prop revolutins. hmmm

[LEASEGUY]

Originally Posted by stonebreaker

Where would that put your redline?

between 5-5500 rpm

[LEASEGUY]

Originally Posted by Jango

First of All,reliability would suffer, unless 6000 - 6500 was only an occasional Burst.

If you're willing to go to a smaller prop, very little need be changed. Perhaps, nothing.

If you're looking at a 2000 RPM increase with a 40% to 50% increase in speed, HP will need to be More than DOUBLED.

Required HP increases expodentially with speed. This would require a TOTAL rebuild of motor - Higher compression, stronger crank, Rods, Higher flowing Heads, complete valve train change, cam , carburation etc. Not exactly an Inexpensive operation.
Less expensive to go to a larger motor.

yeah smaller prop =higher rpm =same boat speed right?

[stonebreaker]

Originally Posted by LEASEGUY

yeah smaller prop =higher rpm =same boat speed right?

Depends on how much power your engine produces at 3000 vs 5000 rpm. I'd say you're over-propped.

[Jango]

You will not be able to spin the same prop at twice the speed by changing to a 1:1 gearbox. If you motor is in Good operating condition,tune etc. and you are currently wide open at 3000 -3500 RPM, you are Overproped. Operating speed should be 4000 RPM plus. Yes, you can get 350-375 HP, but, at a cost.

[LEASEGUY]

Originally Posted by stonebreaker

Depends on how much power your engine produces at 3000 vs 5000 rpm. I'd say you're over-propped.

Am I over proped if I can red line the engine?

with the engine @ 4000 rpms ( max recommended is 4200) shaft turning 2000
the boat moves nice, not fast but nice. anything less than that is too slow

[Frosty]

5000 RPM is way too high for American iron. The RPM needs to be right on the max HP. Why take it higher, your running out of steam up there.

[stonebreaker]

Originally Posted by LEASEGUY

Am I over proped if I can red line the engine?

with the engine @ 4000 rpms ( max recommended is 4200) shaft turning 2000
the boat moves nice, not fast but nice. anything less than that is too slow

Wait, I thought you said you could only turn 3000-3500?

Anyway, the only way you're going to get that engine to 350-400 hp is with a supercharger. If you do a lot of part-throttle cruising, the supercharger might be more fuel-efficient, but for mostly wide open throttle it would be cheaper to just buy a bigger engine.