PUMP vs. PROP
 

Justin Van Dyken wrote:

OK, big question, all takers.

All of my experiance is in jet boats, I have only stepped aboard a
prop boat a couple of times. So naturally I tend to gravity toward
what I know, and I admit that I am probably a little biased and will
defend my little jet boats with vigor. However, in my continual quest
for more power and more speed I have come across many an individual
that will swear up and down that a jet pump is "limited" and a prop
boat is "limitless".

The main arguments are these:

1. You can only force so much water through a jet pump no matter how
much you build the engine.

2. HP for HP a prop boat will have more responsiveness and overall
speed.

3. Lastly there are no cavetation problems that you have with a pump

Now, I would like to find this all out for myself, BUT, you cant
really go down to your local boat dealer, show you drivers license and
take a couple boats for a spin. At least not at the dealers that I
know of.

Does anyone have some light to shine on this subject? Any
experiances? They would be much appreciated.

Thanks,

Justin Van Dyken

PUMP vs. PROP
 

On Wed, 04 Jul 2007 15:58:54 -0700, Justin Van Dyken
wrote:

Does anyone have some light to shine on this subject? Any
experiances? They would be much appreciated.

I've never owned a jet, but those that I have seen have been damned
impressive in terms of weight to power ratio. In terms of fishing,
there are jet boats what will go places that a prop boat won't go even
on trolling motor. And they will perform the same in 6 inches of
water as they will in 120 feet.

We have several jet boat owners here - they will chime in eventually.

For my money, jets are marginally more capable than prop boats in
certian conditions. Consider this - there are several jet boat
ferries operating in commercial service here and in Europe.

That's got to say something for them.

PUMP vs. PROP
 

On Jul 4, 7:25 pm, Short Wave Sportfishing wrote:
On Wed, 04 Jul 2007 15:58:54 -0700,Justin Van Dyken

wrote:
Does anyone have some light to shine on this subject? Any
experiances? They would be much appreciated.

I've never owned a jet, but those that I have seen have been damned
impressive in terms of weight to power ratio. In terms of fishing,
there are jet boats what will go places that a prop boat won't go even
on trolling motor. And they will perform the same in 6 inches of
water as they will in 120 feet.

We have several jet boat owners here - they will chime in eventually.

For my money, jets are marginally more capable than prop boats in
certian conditions. Consider this - there are several jet boat
ferries operating in commercial service here and in Europe.

That's got to say something for them

Justin Van Dyken wrote:

Short Wave,

I agree completely with what you said. But here is where I have
become conflicted. I have a sea doo sportser with a Rotax 720 that
makes 85hp. It makes good speed and power in a small 14.4 foot
boat. But I have to admit, it feels like it is about 20-30 percent
underpowered, which is why I am trying to beef it up now.

I have a friend with a outboard 75hp and he can kill me in speed and
acceleration(his boat is max on the HP anymore and he would sink from
the stern;). However, I have another friend who has a sea doo
speedster. EXACT same boat "hull" as mine, BUT with twin 720cc
putting out 170hp in a 14.5 foot boat, and it is insane on power and
speed. I am inclined to believe that you can put more overall HP
into a jet boat for reasons that I admit I havent figured out. Just
my hypothesis.

Justin

PUMP vs. PROP
 

On Wed, 04 Jul 2007 17:52:27 -0700, Justin Van Dyken
wrote:

On Jul 4, 7:25 pm, Short Wave Sportfishing wrote:
On Wed, 04 Jul 2007 15:58:54 -0700,Justin Van Dyken

wrote:
Does anyone have some light to shine on this subject? Any
experiances? They would be much appreciated.

I've never owned a jet, but those that I have seen have been damned
impressive in terms of weight to power ratio. In terms of fishing,
there are jet boats what will go places that a prop boat won't go even
on trolling motor. And they will perform the same in 6 inches of
water as they will in 120 feet.

We have several jet boat owners here - they will chime in eventually.

For my money, jets are marginally more capable than prop boats in
certian conditions. Consider this - there are several jet boat
ferries operating in commercial service here and in Europe.

That's got to say something for them

Justin Van Dyken wrote:

Short Wave,

I agree completely with what you said. But here is where I have
become conflicted. I have a sea doo sportser with a Rotax 720 that
makes 85hp. It makes good speed and power in a small 14.4 foot
boat. But I have to admit, it feels like it is about 20-30 percent
underpowered, which is why I am trying to beef it up now.

I have a friend with a outboard 75hp and he can kill me in speed and
acceleration(his boat is max on the HP anymore and he would sink from
the stern;). However, I have another friend who has a sea doo
speedster. EXACT same boat "hull" as mine, BUT with twin 720cc
putting out 170hp in a 14.5 foot boat, and it is insane on power and
speed. I am inclined to believe that you can put more overall HP
into a jet boat for reasons that I admit I havent figured out. Just
my hypothesis.

I'm not familiar with jets, but just guessing, I would imagine that
it's not so much the engine - 85 hp is a lot for 14 1/2 feet.

I suspect that there is something going on in the jet system - perhaps
a bad impeller or a clogged intake screen - something along those
lines. You might not be able to out hole shot a prop, but
accelleration when rolling and top end should eat your friend's boat
alive.

I'd take a look at upgrading the jet or seeing if there is something
screwy with the jet before I went tearing into the engine or bolting
on something.

PUMP vs. PROP
 

"Short Wave Sportfishing" wrote in message
...

For my money, jets are marginally more capable than prop boats in
certian conditions. Consider this - there are several jet boat
ferries operating in commercial service here and in Europe.


I took one of these (can't recall which one, specifically) from Seattle to
Victoria round trip. I had a hand-held GPS with me and it was reading 40
statute mph at cruise. Four jets, each powered by a big-assed turbo diesel.
I asked one of the crew about fuel consumption at that speed. He reported a
number that I no longer remember, but it was astronomical.

http://www.clippervacations.com/ferry/

PUMP vs. PROP
 

"RG" wrote in message
. ..

"Short Wave Sportfishing" wrote in message
...

For my money, jets are marginally more capable than prop boats in
certian conditions. Consider this - there are several jet boat
ferries operating in commercial service here and in Europe.


I took one of these (can't recall which one, specifically) from Seattle to
Victoria round trip. I had a hand-held GPS with me and it was reading 40
statute mph at cruise. Four jets, each powered by a big-assed turbo
diesel. I asked one of the crew about fuel consumption at that speed. He
reported a number that I no longer remember, but it was astronomical.

http://www.clippervacations.com/ferry/


Crap, the link didn't navigate to the vessel info page. Click the vessel
information button.

PUMP vs. PROP
 

Justin Van Dyken wrote:
On Jul 4, 7:25 pm, Short Wave Sportfishing wrote:
On Wed, 04 Jul 2007 15:58:54 -0700,Justin Van Dyken

wrote:
Does anyone have some light to shine on this subject? Any
experiances? They would be much appreciated.
I've never owned a jet, but those that I have seen have been damned
impressive in terms of weight to power ratio. In terms of fishing,
there are jet boats what will go places that a prop boat won't go even
on trolling motor. And they will perform the same in 6 inches of
water as they will in 120 feet.

We have several jet boat owners here - they will chime in eventually.

For my money, jets are marginally more capable than prop boats in
certian conditions. Consider this - there are several jet boat
ferries operating in commercial service here and in Europe.

That's got to say something for them

Justin Van Dyken wrote:

Short Wave,

I agree completely with what you said. But here is where I have
become conflicted. I have a sea doo sportser with a Rotax 720 that
makes 85hp. It makes good speed and power in a small 14.4 foot
boat. But I have to admit, it feels like it is about 20-30 percent
underpowered, which is why I am trying to beef it up now.

I have a friend with a outboard 75hp and he can kill me in speed and
acceleration(his boat is max on the HP anymore and he would sink from
the stern;). However, I have another friend who has a sea doo
speedster. EXACT same boat "hull" as mine, BUT with twin 720cc
putting out 170hp in a 14.5 foot boat, and it is insane on power and
speed. I am inclined to believe that you can put more overall HP
into a jet boat for reasons that I admit I havent figured out. Just
my hypothesis.

Justin


The 10'10" 215 hp supercharged SeaDoo is an amazing piece of equipment.
I've ridden two recently, the 3-up model, and 0-60 mph is almost
instantaneous. The 2007(RXT) is still in break-in, but showed 68 mph on
a quick full-throttle blast.

SS impeller, 12 vane stator, single stage. Weighs ~900 lbs. dry, 16
gallon gas tank.

I did a couple of Hamilton Turns and nearly sunk the machine even at
lower speeds. The bow digs right down when you slam on the brakes.

Acceleration & top speed far above my 1800 lb. 220hp 16' inboard, but
only 1/2 the seating capacity.

Rob

PUMP vs. PROP
 

Short Wave Sportfishing wrote in
:

On Wed, 04 Jul 2007 15:58:54 -0700, Justin Van Dyken
wrote:

Does anyone have some light to shine on this subject? Any
experiances? They would be much appreciated.

I've never owned a jet, but those that I have seen have been damned
impressive in terms of weight to power ratio. In terms of fishing,
there are jet boats what will go places that a prop boat won't go even
on trolling motor. And they will perform the same in 6 inches of
water as they will in 120 feet.

We have several jet boat owners here - they will chime in eventually.

For my money, jets are marginally more capable than prop boats in
certian conditions. Consider this - there are several jet boat
ferries operating in commercial service here and in Europe.

That's got to say something for them.

"Several" is an understatement......there are many, most of which are using
computer controls to increase maneuverability

PUMP vs. PROP
 

Now, I would like to find this all out for myself, BUT, you cant
really go down to your local boat dealer, show you drivers license and
take a couple boats for a spin. At least not at the dealers that I
know of.

Does anyone have some light to shine on this subject? Any
experiances? They would be much appreciated.

Thanks,

Justin Van Dyken



The rule of thumb for the small-river-jet-boaters in my neck of the woods is
that switching from prop to jet setup equals a 50% reduction in real HP at
the business end. This is probably why you see (used to see?) lots of
2-stroke jet boats- higher power-to-weight ratio. This is probably also why
jet boats suck twice as much gas as prop boats.

PUMP vs. PROP
 

All depends what you want to do. My 21 footer with 300hp runs 95mph. Try
that with a jet boat drive.