RPM loss on heavy load.

[Danhercules]

When a prop trims out and speeds up, there is a RPM gain.
If a jetboat is loaded down with fuel, lots of people, will there be a RPM gain if the load is taken off the boat?
Any thoughts on this? :idea:

[squirt'nmyload]

maybe.....i've never payed attention when i was running light

[Jetaholic]

Actually...as a prop boat gains speed, the prop unloads, therefore allowing the RPM gain.
A jet boat can give all thrust at once...from a dead stop you can achieve max RPM from a dead stop. The amount of people in the boat will have no effect on actual RPM, but will have an effect on max speed. This is because a jet boat can achieve max available thrust right out of the gate, but the weight of the boat, people, cargo, etc etc...will determine max available MPH.
To summarize, on a jet boat, weight has no effect on max RPM, but has everything to do with max MPH.
Make sense?

[SmokinLowriderSS]

Like Jetaholic said, "no, there won't be".
No change.

[McIntyrelocal]

if you want a little more rpm you will probably need to put a little more blocker in your intake loader and take a little bit of water away from the pump that might help the motor rpm.

[Danhercules]

Its not that I want RPM at all. It was just a question. I had 9 people in my boat this weekend and it just got my mind going.

[McIntyrelocal]

gotcha .

[Ken F]

You can tie your jetboat to a pier and it will still turn the same rpm.

[Danhercules]

Will the ski tow hold? Will the pier?

[centerhill condor]

Will the ski tow hold? Will the pier?
give it a try...and take a camera and cell phone.
CC

[Squirtin Thunder]

You can tie your jetboat to a pier and it will still turn the same rpm.
I honestly don't think it will if you have a tight pump.
Mine on the other hand should with no problem right now.:D

[widowmaker]

if you want a little more rpm you will probably need to put a little more blocker in your intake loader and take a little bit of water away from the pump that might help the motor rpm.
Blockers can affect lots of things, or they can add lift for the rear of the boat. Each boat is affected very differently. For instance at bakersfield, I tried a slight blocker on one pass and it cavitated out of the hole unlike the loader before with no blocker and actually pushed the nose down slightly and I lost 4 mph on the top end, and it had zero affect on rpm.
I personally wouldnt run a blocker to increase rpm, I would cut the impeller down. If you do see a gain in rpm with a blocker, I would think that the pump is running ineffeciently thus creating cavitation which it not a good thing. just my two cents.

[McIntyrelocal]

Blockers can affect lots of things, or they can add lift for the rear of the boat. Each boat is affected very differently. For instance at bakersfield, I tried a slight blocker on one pass and it cavitated out of the hole unlike the loader before with no blocker and actually pushed the nose down slightly and I lost 4 mph on the top end, and it had zero affect on rpm.
I personally wouldnt run a blocker to increase rpm, I would cut the impeller down. If you do see a gain in rpm with a blocker, I would think that the pump is running ineffeciently thus creating cavitation which it not a good thing. just my two cents.
i agree but if you were trying to gain rpm that is probably the cheapest least invasive way, just a suggestion. I run 6 in of blocker in mine advised by tommy my boat is still way to wet but i dont have alot of horse power to lift the boat yet.

[widowmaker]

i agree but if you were trying to gain rpm that is probably the cheapest least invasive way, just a suggestion. I run 6 in of blocker in mine advised by tommy my boat is still way to wet but i dont have alot of horse power to lift the boat yet.
Cool, have you tried a wedge to gain more lift? I flipped my wedge and picked up speed, i.e. lower thrust angle.

[McIntyrelocal]

Cool, have you tried a wedge to gain more lift? I flipped my wedge and picked up speed, i.e. lower thrust angle.
not yet i got it done so late this year i just wanted to use it but im gonna put a keel on this winter then ill start trying to nail the setup.it will have a different motor to this one just a stocker.

[Jetaholic]

You can tie your jetboat to a pier and it will still turn the same rpm.
FINALLY!!! Someone who actually understands that no matter what you're just turning a water pump. It's still gonna pump water...the engine and pump have no idea and could care less what the fock they're attached to! Still the same RPM all the time no matter what. The actual weight load will only determine max MPH...RPM is all in the impeller and how much horsepower/torque the motor can make at given RPMs...the impeller size is just like the rear end gear ratio in a car. Except you're in water...a liquid...not on pavement. The pump will always pump water no matter what...the engine will always spin it the same RPM no matter what...the only thing the weight of the vessel will ever determine is the max MPH.
Will the ski tow hold? Will the pier?
I'll answer this one with another question...
Is the boat on a treadmill? :D