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View Full Version : Jets vs propeller for performance



riverrat321
01-04-2005, 06:53 AM
Hey guys i'm just wondering how jet units compare to propeller driven craft for performance in both acceleration and straight line?

crazy horse
01-04-2005, 08:47 AM
No contest, If you have the same HP on the same hull then the prop driven boat will out run the jet all day. Jet pumps keep the hull glued to the water so it takes all kinds a horsepower to get them to move.

KIBBEY
01-04-2005, 12:50 PM
crazy horse hit it right on,jets might look good but there not worth the money...theres only one way to go :D :D

150aintenuff
01-04-2005, 09:52 PM
NO CONTEST PROPS ARE BETTER!!!! 150hp prop will run like 220 in jet form... so of you had a 1000 hp inboard jet a 600 hp prop would run with it pretty easilly if not faster...

jets are only about 60-70% efficient MAX where a prop can be up to 95% efficient
Jets do however have their purpose...THEY RUN EXTREEMLY SHALLOW!!! some less than 4" of water...

riverrat321
01-04-2005, 10:26 PM
Wow, thanks for the info guys. Just thought it might be an alternative but not for me by the looks of it.

150aintenuff
01-05-2005, 12:56 PM
The other advantage to Jets is their SAFETY!!!!! no chance of getting hurt from catching a propellerblade with a leg or worse, so if you have little ones that like to swim around the boat then a jet has a great advantage.

Rampager
01-05-2005, 11:00 PM
Of course everyone happened to forget to mention neck snapping acceleration and handling thats hard to argue with.
Ask more questions and take some rides before you make a decision. Jetboats can be a total blast and the major inefficiency thats was spoken of isn't as bad as it sounds(I don't recall outboards being great on gas either) Upkeep and initial cost is another factor. Try rebuilding a lower unit or replacing a prop and see what hurts more....( the entire jetdrive is like $3000)
Not saying one is better than the other just look at the whole picture

Cheers

p.s. if you ain't hitting bottom...you're not boating! ;)

150aintenuff
01-06-2005, 03:58 AM
Rampager... holeshot and excelleration is a function of power to weight
give me 600 hp in the form of 2 merc 300X's on a 20' boat and I garentee Ill break your neck if not throw you out of the boat... not to mention that she would run WAY over 150mph if you could get her to hook up and stay below rev limiters.....that same 600 hp in jet form might have similar holeshot but It wont even come close in top end or midrange.... also if you want to go apples to apples.... take a 454 BBC 300hp prop and a marinepower 454 BBC 300 hp jet... the prop wins in topend and midrange most if not all the time....

Jets are like the short kid in school.. SOB is fast to get going but the bigger kids tackle him once down feild... we long legged people just take a while to get going....but were faster once the homestreach is in sight.

efficiency isnt a function of MPG or GPH... it is a function of Power in to power out... Jets loose efficency in powerout due to slipage... it takes 200hp in to recieve 140hp out so in total theory the prop is 30% more efficient, although pump design and engeneering are getting that number closer to 20%...

ALSO... I have personally taken my propdrive in places that a jet couldnt ... like 15miles off shore in 8-10 swells with 4-6" windwaves ontop... jets cant pull enough water when they are out of the water 1/2 the time... granted you can go shallower than I but I use my boat for fishing as well what i catch isnt caught in less than 6 feet of water anyway... my .02

Jets do have their aplications as do propellers, so ultimatly the choice is answered by the type of boating you do and where you do it. If $$$ were no object i would have an OB prop on a jackplate with a bay kit so i could go both ways but my hulll is designed for that type of aplication as it is a whitewater sled with a pad V hull...

GP-1
01-06-2005, 12:29 PM
[give me 600 hp in the form of 2 merc 300X's on a 20' boat and I garentee Ill break your neck if not throw you out of the boat... not to mention that she would run WAY over 150mph if you could get her to hook up and stay below rev limiters



OK, this is the stuff that gets to me.... Where is this hypothetical 20' boat that goes "WAY over 150"? I'm certainly not the authority, but how many people on here have twin-outboard, 150 mph boats??? I don't don't know of anybody... not even close.. The fastest boat I know of goes 140ish with probably around 400 horsepower, but it only does that because the guy driving it has very good skills and a questionable self-preservation instinct.. Put me in it, and MAYBE it'll see 120 -- maybe...

Anyway, I wanna see that 20', 2x300X boat.. What's it gonna be, a Grandsport? OK, maybe a Skater...? While it might be possible, I haven't seen it done.. All the big, twin outboard boats I've seen (mostly with 280's) run 120-125 -- that's a long, long way from "way over 150"..

triple dude
01-06-2005, 03:35 PM
I'm probably one of the few jetboat owners on scream & fly, and for the most part, you guys' opinions are correct. For an everyday, take the family out boat, it's just a matter of what you need. I needed a boat that would haul a bunch of people and coolers, have some decent speed and of course, look good. That put me in the bowrider category and there are few low profile outboard bowriders out there. As one of you mentioned, an advantage is safety with no prop. Another is the ability to go in the shallows (unless there's lots of weeds). Probably my favorite is being able to run down to the local auto parts store to buy parts at REASONABLE prices. As far as speed, the stock 454 is good for 60mph with one person and light fuel load. Easy prey for MANY outboards. But even with a bunch of people inside, the engine torque still allows skiing and decent speed.

GP-1
01-06-2005, 03:51 PM
I'm probably one of the few jetboat owners on scream & fly, and for the most part, you guys' opinions are correct. For an everyday, take the family out boat, it's just a matter of what you need. I needed a boat that would haul a bunch of people and coolers, have some decent speed and of course, look good. That put me in the bowrider category and there are few low profile outboard bowriders out there. As one of you mentioned, an advantage is safety with no prop. Another is the ability to go in the shallows (unless there's lots of weeds). Probably my favorite is being able to run down to the local auto parts store to buy parts at REASONABLE prices. As far as speed, the stock 454 is good for 60mph with one person and light fuel load. Easy prey for MANY outboards. But even with a bunch of people inside, the engine torque still allows skiing and decent speed.


I didn't know they made two-stroke 454's :) .....

triple dude
01-06-2005, 03:55 PM
If only I could get the bean oil smell... ;)

Chummy
01-07-2005, 02:06 PM
The only jet i have seen that were in my opinion COOL were 21' sports from here:

http://www.eagleracing.ca/RMedia/

Rampager
01-07-2005, 06:26 PM
I guess I own a cool jet then ;)

I'm not quite with you on the slippage issue as technically jets don't "slip", at least not like a prop does and thats why jets have good holeshot. The jetpump does not need to be moving through the water to run efficiently, it just needs to remain fed with water and that "can" happen when stationary(or launching) You cannot just put as much power as you want to a prop and expect it to hook up. Yes obviously extremely rough water impeeds that ability to keep the jet fed.
I think one needs to look a whole lot more at what the aluminum hull guys are doing to get a better idea of modern technology in jetboats. Eagles and that type of boat are getting amazing performance from the jets some even with smallblocks and NO prop boat is doing what they do to a beaverdam(more than once anyway lol) :D
If i boated on the ocean that would be another thing but even as a lake boat I love my jet

Cheers

jrumon
01-08-2005, 12:12 AM
SWEAT BOAT... Wonder what my wife would say to a boat with a ROLL-BAR!!!

All the jets I've owned or ridden in accellerated very hard...

My 21 Daytona Jet with a supercharged monster would get mid 80's and drink about a billion gallons of fuel a second (OK... it was not quite that bad but close)! From a dead dig or just planed out, this thing would SMASH you in the seats like no other... pulling G's on accelleration is almost as fun at top end speed rush. It's all a compromise... PERFORMANCE BOATING is FUN no matter what the make, model, or power choices!!!!!!!!!!! :D

Rampager
01-08-2005, 01:10 AM
I haven't even got the boat yet! lol

My old jet got looks as it was rare around here but yea that rollcage will add some serious "WTF is THAT?!" factor to my boating days I'm sure
I can't wait to get it rigged, throw about 600 hp in it and get her setup to fly.
The 105 MPH pass video on Eagle's site had me sold.
For the record this is a 21.5 tunnel not a sport. Hull is around 600 lbs and will do over 90 with 575+ hp. I believe top racers are running these boats upwards of 120 mph and still hitting bottom here and there.

THIS is extreme boating ;)

Cheers

jrumon
01-08-2005, 10:42 AM
That thing is kick-a$$!!! Kind of like a jet-sprint on steroids!!! :eek:

I'd love to buy or build one of those JET-SPRINT BOATS!!! Seems like one of those would be a great neucence to those pesty PWC's and a hell of a lot of FUN! ;)

Did you ever see that aluminum cat with twin LS1 V8's and jets that was for sale about a year back???? THAT was the "BADDEST" of all JET BOATS!!! :cool:

Unchained
01-10-2005, 07:19 AM
This subject has been thrashed to death.
Look at this web site and check out the boat pictures from each of the classes.

http://www.kentuckylake.org/links/kdba.htm

There are many jets that run strong in the 8 sec class.
There are a few that run in the mid 7's

I've been to many boat drags where they use TIMING LIGHTS.
There are some fast outboreds out there in the 10 sec class, a few in the 9 sec class, I don't recall ever seeing one in the 8 sec class.
Maybe there are some but they don't run where there are timing lights?

I have nothing against outboreds but the posts are so slanted here that it is a joke.

150aintenuff
01-10-2005, 06:02 PM
unchainde i never said outboards exclusivly... there are I/O and inboard props that run in 7-8 seconds....GP1 what would the 20XD bullet bassboat run with twin 300X on it as it will run 100 with a single.... that was my hypothetical example.... yes it was hypothetical.... but as for comparison of HP to weight it would be about the same as a 600 hp BBC and jet pump assembly.... Rampager you do have a nice boat that is very capible as it was a class winning hull and eagle boats are GREAT products..

BTW those boats jumping the beaver dams were Sportjet boats if i remember correctly

I have the video on my computer so I will rewatch and varify and edit if necessary but cool none the less.. As an owner of an Aluminum Jetboat hull (mine is a fishing hull) I can tell you they have Great potential in eather power and propultion option but it is ALL a mater of preference and usage that dictates a persons power choice more than anything.... Unchained I know you have a Damn hot boat with power to spare im sure but what would that boat of yours do as a V drive???? or with an Arnison???? I bet it would loose some holeshot but topend speed would go up substantially.... Just another THEOIRETICAL proposition.....

RSM
01-10-2005, 08:18 PM
I/O's that run 7 seconds :confused: What kind of boat, motor and outdrive are they running? Not trying to be a smartass but I have never herd of that, not to say it dosn't happen but it just sounds funny :D

Unchained
01-11-2005, 08:01 AM
I don't know of any fast I/O's at the drags. Who brought up I/O's ?

Here's a couple jet boats that run in the 7's with No blower or nitrous.

http://www.dragboats.com/images/gallery/03_10_NJBA_2121_334.jpg

http://www.dragboats.com/images/gallery/04_04_IHBA_0603_699.jpg

As far as my setup I'm sure it would have a faster ultimate top speed as a V drive but I don't care for all the V drive negatives.
Accelleration is what I boat for, ultimate top speed is far less important.
I'm just the opposite of the outboard guys.

150aintenuff
01-11-2005, 04:04 PM
I ment to say inboards and v drives.... my bad....

150aintenuff
01-11-2005, 04:09 PM
As far as my setup I'm sure it would have a faster ultimate top speed as a V drive but I don't care for all the V drive negatives.
Accelleration is what I boat for, ultimate top speed is far less important.
I'm just the opposite of the outboard guys.[/QUOTE]


Like i said before we choose power and propultion for our use.....

jets have good holeshot.... but if speed is key steel to water is the only way to go...


again that is not saying jets are slow... just have less potential per HP tan a prop.

JW
01-16-2005, 09:08 AM
Since I/O got mentioned :p there was an article in one of my boat mags recently where they took a normal family style bow-rider with the 2 bbl. 4.3 V6 Alpha I/O and put it against the same boat with a Merc V6 240 horse jet drive. For most of the tests, the jet drive and the I/O were very very close, with the jet package besting the I/O package occasionally. Jet drive technology is getting very good. The only place where the Merc V6 240 horse jet drive fell down compared to the I/O was in the load carrying capability. The test was full capacity loaded boat AND pulling up a skier. The Jet drive didn't have the oomph compared to the I/O in this scenario for pulling up a skier.
Was a very interesting article.

Unchained
01-16-2005, 11:35 AM
I guess I wasn't supposed to borrow those pictures from Dragboats.com

Now I can't edit the post either.

" I've been bad Ren " ...............

Maybe the moderator can remove the pictures ?

150aintenuff
01-17-2005, 01:06 AM
I guess I wasn't supposed to borrow those pictures from Dragboats.com

Now I can't edit the post either.

" I've been bad Ren " ...............

Maybe the moderator can remove the pictures ? :mad: :mad:


they were used in context and to express your opinion in a legal manor and since the interweb is free domain i cant see why you got dinged for using a pic in your post that was off another website... BEsides who does it hurt anyway... EVERYONE uses items for examples from another websites...at least from time to time... IMHO the post wouldnt be complete without the pics and your argument for them.. I may not agree with that particular opinion but you have backed your opinion with fact and that is all we all can ask for.. IMO the pics should stay.

ALSO their trademark is Still on the pics SO they dont lose any $$$ by them being used elsewhere on the net Because you still have to go to their site to see more... BTW IT INCREASES advertises their "product" by them being out there and I may not agree with greg on this but It doesnt hurt anything if there is a few pics used here and there from other sites.. it is what makes this board so great... So many opinions with so many different facts that backs their opinions up .. I may take a beating here but if i do i deserve it.

jrumon
01-17-2005, 10:10 AM
In that artical, did they post MPH and MPG or GPH??? And was the tow different powertrains compaired in the SAME hull??? Curious... Jim.

P.S. I would love to do a "side by side" comparison with my Larson 176SEi Flyer Jet

>>>MY Larson 176SEi Flyer Jet with a 225HP 4.3L GM-V6 and full size Legond Jet pump (marketed by Volvo-Penta as the DJX series).
>>>VRS<<<
>>> the exact same boat with the Volvo Penta same 225hp 4.3L GM-V6 and their standard stern drive.

I wonder how the ACTUAL numbers would compare SIDE BY SIDE:
>holeshot
>top end
>crusing
>fuel economy at various speeds
>GPH at various rpm's
>pulling up skiers
>etc.

Seems like these are the kinda tests our boating magizines should be doing!!!

drag120
01-19-2005, 06:32 PM
Unchained, there's a good thread on turbos in the general information section. Some talk about 2 strokes and some on 4 strokes. I didn't see any lag when you took me for a ride. Tom

150aintenuff
01-20-2005, 01:29 AM
his is properly set up... drive a later 1990's PSD and then tell me you dont feel any lag.... Also and VVVVVVVVVSSSSSSSSSSSHHHHHHSSSSSHHHHSSSS sound is lag... turbos winding up.

Unchained
01-20-2005, 04:50 PM
Thanks Tom,

I went to great lengths to be sure that the boat motor wasn't hampered by turbo lag. Especially since I'm using such large turbo's.
I mounted the wastegates right on the turbine housing to keep the exhaust pipe volume down to a minimum.
I have the pipes separated right up to the turbine housing flange.
I think that the port injected EFI system helps greatly as well as the turbine housing sizing. I've recorded 17 # boost in 1 sec.

150aintenuff
01-21-2005, 02:16 PM
like i said unchained is PROPERLY set up.

speed master
02-11-2005, 11:03 AM
as a retired marine engineer,what you might want to consider in order to put things into perspective, is that a jet pump is basically a modified propeller stuck in a close tolerance housing. a surface drive prop. uses an augering or screw to push a boat at low speeds while submerged and a reaction or thrust { from throwing the rooster tail] while riding on the surface. A jet pump uses reaction principal all the time. The fact that water traveling at high velocity through a pump must make SEVERAL changes in direction compared to a cavitating props. one change in direction can account for theoretical advantages right there. All the pros and cons discussed so far are very valid, examine your priorities gentlemen. I might add that a jt pump loses steerage with loss of power, loses suction [ power] when bouncing off of waves. BUT, jet skis would be literally unmarketable with props on them. Your basic pro comp is a 600 hp.2 bladed meat cleaver

speed master
02-11-2005, 01:01 PM
I forgot to add that in a jet pump there are also frictional losses in between high velocity water and the , housing, impeller, stator, & nozzle. a prop is free wheeling and out ther by it self. Theoreticaly you could set it up so the shaft is surface riding on a tunnel or hydro.

hallnass
02-18-2005, 10:07 PM
Well guys I have both and I use the effiency of my outboard for my ride around and
the jet to hurt the feelings of all the outboard guys. mine will leave from an idle on the spray. I have raced outboards with nitrous on light hulls and hole shot them. It does take more power to do it but I will chanlenge mr 2 or 3 outboards in the 1/4 mile any day. I can rebuild my motor cheaper too. Outboard parts are too expensive.
If you want bang for your buck buy an old earl smith gull wing and put a 468 with a
little nos and you will have a dependable ride that will push 100 and not cost as much for the whole rig as your 2.5 cost you. more fun per $

david martin
12-05-2005, 09:51 PM
i do not want to argue but i owne 2 outboard boats 1 v-drive boat 2 jet boats and they all are different in thier own way i think the out board is the way to go 2 stroke not a lot to go wrong small block or big block lots to worry about i seem to blow the engines quit often in my v-drive and jet boats i seem to get a little throttle happy i love the speed good luck with that :p not apples to apples by any means

speed master
12-06-2005, 01:59 PM
If you are having trouble holding automotive engines together in a hi-performance boat, just imagine taking a coffee cup and filling it half full of motor oil. Then attach it solidy to your boat and go for a ride;I hope your not wearing your good bathing suit, and please do not polute. Try dry sumping your motor, you'll be pleasantly surprised!

david martin
12-06-2005, 03:55 PM
my v-drive has been running 3 years now with the same motor and not 1 problem since i installed an msd box with a rev limiter no more rod knocks i put a rebuilt 460 ford in my kona mini cruiser that i built my self and no more problems those are the 2 boats i had problems with and they seem to be holding together just fine although my outboards are so quiet if i had a real problem with auto or marine inboards i would not own so many of them

Steven
12-07-2005, 03:54 PM
i just picked up a 68 rodgers flatbottom. thats what the title says, but theres no identification on it anywhere. the boat is in good condition. it had a big block 468 and a shorty powerglide. i rode in it a few years ago and it didnt seem to perform like it should. turns out the motor was junk. anyway, we bought the boat, less motor, and im wondering what a healthy small block would do without the transmission. the cassel box can be disengaged. seems like alot of weight will be lost with this setup. i dont know anything about v-drives. thanks

david martin
12-07-2005, 04:54 PM
a healthy small block would be nice it will perform well in a v-drive boat,what degree casale unit is in the boat and what prop are you running (i have a 2 blade menkins on mine seems to work good for top end)if you remove the tranny you will have to let the motor warm up in neutral shut the motor off and restart it in gear also you wont have reverse strickly go forward:p good looking boat by the way

hallnass
12-07-2005, 09:22 PM
:D I'll throw my 2 cents in on this subject. If you want performance it is much cheaper to get big power from a big block and does not weigh that much more for the power you will get in return. I have a 565 in my jet and you will spend more on a big inch small block than i spent on the 565 and will have nowhere near as much power. you can get 600 plus horsepower from a warmed over 454 and will pay big to get that from a small block. It sucks to have a hot rod boat that does not run like it looks.
If you need any help or suggestions feel free to e-mail me. I can help you with a combo that will fit your budget. and for the record my motors run all year too. and I have spent more on the outboards in the last 5 years than I have on the jet.
Good luck
Keith














good luck
Keith

david martin
12-07-2005, 10:52 PM
Where do you live in east Texas?I am going to lake conroe for christmas to see my brother.I believe in the big block,I have one in both my jet boats and one in my v-drive. I am currently building a small block for my v-drive.I have seen a couple small block v-drives beat big block jet boats,it does take more power for a jet pump, what type of jet boat are you running?That thing has to fly with that kind of power.My brother in texas is looking for a strong big block chevy short block if you know of one for sale in or around conroe area.,let me know thanks.

hallnass
12-09-2005, 06:59 PM
:D Hello David,

I am in marshall tx. I mostly run on lake o pines and caddo, also some on the red river in shreveport and we play at broken bow lake in ok. on holiday weekends.
I run a youngblood picklefork 18.5ft it has a dominator pump with dons inducer and
a triple a impeller. It will run over 100 mph on the motor and it has a fogger and a
plate nitrous system. I have not found anything that requires two stages yet. you can see some pics and videos on youngbloodjetboats.com look under links july05 and labor day. There is a video of my 15 year old son racing a blown tx 19 with no nitrous under labor day, and a video of me racing a blown alky youngblood under
july05 link.
on the motor my neighbor has a drag car that runs in the 7's and his motor is for sale
it is a 598 with big chief heads, sheet metal intake, two foggers and makes 1198hp with no nitrous. I will ask him if he knows of any other engines for sale. How big and how much power do you want and what kind of $ do you want to spend.
e-mail me if you want more info.
keith

david martin
12-09-2005, 08:19 PM
hello keith to start off, I have never seen a slow young blood. I love to see father and son in boats , that is awsome!I am teaching my son how to run my kona jet boat (460 little modified with a berkley je pump,droop snoot and place diverter)nothing like your boat,my son is 13 years old.I checked out your site and your boats are impressive.My brother is looking at an L-88 427 with complete roller set up and a tunnel ram with 2 holley dominator carbs,I think this guy is holding it for him in canyon lake but if this falls through then i will get with you.My brother is running a shovel nose hydro with a v-drive set up and my sleekcraft aristocrat tunnel hull with an 175 merc outboard on lake conroe.I dont think you are very far from that lake. Sounds like you could have fun out there any way take care and thanks for getting back with me.:)

If my brother does not get this motor he is looking to spend $4500.00

thanks again keith;)