View Full Version : looking for more HP

05-10-08, 02:38 PM
i am new to PWC's. i have quite a varied background of motorcycle racing and modifying bikes.so last year a bunch of my buddies went and baught PWC's for a new adventure. well anyway ive been very satisfied with my 07 seadoo gti till i tried pulling a 4 seater viper tube ..it couldnt plane it out.now one freind got the seadoo gti-se and it could pull it (barelly).looking at the specs of course both are the same exact PWC just diferent color and HP. the engine is the same size but mine is like what 130HP and his is 155HP. and plus theres one more model boasting more HP then that with the same engine befor they go into turbo charged and larger engine. so OUR question is what is making the difference in HP on the same size engine and how can we tuen up the HP?

i want to be able to pull the viper 4 tube with 4 large adults without changing my prop and loosing my top end

05-12-08, 05:31 AM
come on now !!!!! isnt there anybody that has any knowledge of performance mods for these things:banghead:

05-12-08, 05:11 PM
I'm just totally amazed at members who come in, looking for answers on what they can do to make their PWC faster, for whatever reason. Whether it's because you came in 2nd place in a race or you can't pull a wake board.
Let me help you out. You want something with more horsepower, buy it!
I'm not being sarcastic, I'm just being a realist. If your looking at the differences between the GTI and the GTI SE, there are none, engine wise anyway. The only real difference is the GTI was made also as a rental (which are always built slower) and the GTI SE wasn't.
They both have the 1503 4-TEC engine in them.
Now, to answer your other question. The 4-TEC engine has been around now for several years. Outside of the supercharger, which makes the most horsepower now, 255 I believe, the differences in making that horsepower are in the bore and stroke. The carb jetting and a few other small changes, maybe the degree in the pitch of the impeller.
You can dump all the money you want, getting into the RIVA mods if you like, but you'll never be satisified.
The 4 stroke, 1503 engine is now so widely used in the Seadoo watercraft, it's all but impossible to keep up with all the small, internal changes that crank up the horsepower. But you have to be satisfied with what you got, because you'll not be able to gain any of what the others have. That's just the way yours was built...............:nopity:

05-12-08, 06:23 PM
i was affraid that ,that was gonna be the answer to my question. basicly what you buy is what you get. im so used to buying a performance toy and modifying it. i am still very satisfied with my GTI

thank you very much:hurray:

05-13-08, 01:21 AM
please completly disregard my above statement. at first i thought skatman's coments were true till we did more research.

im calling you out skatman. if you truely know your stuff. put out! :boxing_smiley: or dont coment in the first place. remember we were all squids at some point.

for those who are looking for mods wether its to pull that skier or maby get into racing. heres a start for you


i drag race a street stock 07 gsxr1000 if i wanted a hyabusa i would of baught one. i run a ltz400 quad if i wanted to ride my ltr450 i would.you see my point you dont have to buy the fastest to be the fastest

so why dont you take of your suite, go don your leather jacket and hop on your harley and pretend that your hard core biker and do somthin usefull like ride for toys for tot's . haha J/K


05-13-08, 02:14 AM
intercoolers are worth 30-35 hp if you wanted to mod a better choice might have been the RXP you can start at 215 hp and easley get to 300 hp with mods to the SC, Intercooler ,exhaust, ECU and injectors and of course the handling mods to go with them.

05-13-08, 10:57 AM
John, I think you took my post the wrong way. I myself have built high performance engines, mostly in street rods. My first was a 283cu.in. and up into the 327, 350 and small block 400's. I use to race my trucks at the local drag track and also had a nitrous boosted, air shifted 750-4 Honda motorcycle. Most of my V-8's were only equipped, after rebuilds (which included my own caustic boil out vat) with a Competition Cam with a 486 total duration so that I didn't have to go with a stall speed torque converter. I used a high volume oil pump, gas cooler, removed the fan for extra horsepower, cooling to the radiator with an electric fan that I rigged to a temperature control switch. I topped it with a 6" Weind or Edlebrock high rise intake, with a 2" spacer with a choice of running my Holly 650cfm with vacuum secondary's or my 850 double pumper (which I only used on the week-ends due to fuel guzzling). I dumped the standard 1.96 heads for the 2.02 for more exhaust flow and a set of headers. So you see, I'm no stranger to building/modifying engines, I've just learned, through experience, that the Rotax engine is already built for high performance, with dual carbs or fuel injection and an exhaust system that allows an increased exhaust gas flow rate, that changes according to the amount of fuel/air mix you send through it. The new engines (4-TEC supercharged, 255 hp) equipped with a computer controlled system, the EMS working with the ECM and MPEM, that moniters system functions and changes them according to sensor input, that trying to "mod" them is a waste of time and money.
Sure, there will always be some company out there to sell you anything you want, claiming to do "miracles" to your output. Thats true in any product you buy. I call it the "sucker" rule. If someome will buy it and theres a market for it, I'll make it and promise it can blow you away! How many times have you heard that line, only to be dis-appointed after you bought it? But truth is, by the time you invest enough money to gain that extra "noticeable" horsepower, you could have bought one with the same power you just paid out the "yang-yang for.
I bought a re-manafactured impeller for $30 bucks from SBT. I got a bud, who has a Honda, who paid over $200 bucks for that pretty Solas!....Guess what, he's really not blowing me away in a race.....
So, my point, yeah, there are mods out there that can give you a few extra ponies, but when you start making changes, you better make sure that ALL your systems are compatible with them, or you'll start getting errors in sensor pick-up or some other fault, if not an overheating problem.
If it's a must for you to do a mod, I'd suggest you visit the Riva performance site and look through there 1,2 and 3 stage kits. But it sure is a lot of money, for an extra pony.......
So if I mis-lead you by my first post, I apologize, that wasn't my intention. I look at cost verses return and I just can't seem to justify that expense without the thought of just buying a new ski with more power already there. :cheers:
Oh, BTW, expect engine life span to be dramatically reduced in "modding" out an engine, you say you race, I'm sure you already know that, but in my defense, in your first post, you made no mention that you wanted to build for "racing"........because that's a completly different set of circumstances. And in communicating in debate, you don't have to take a nasty tone. Just call them out!...ask them why the comment was made in that particular way. There may be a good reason behind it that you may have overlooked.....:leaving:

05-13-08, 12:17 PM
please completly disregard my above statement. at first i thought skatman's coments were true till we did more research.

im calling you out skatman. if you truely know your stuff. put out! :boxing_smiley: or dont coment in the first place. remember we were all squids at some point.

for those who are looking for mods wether its to pull that skier or maby get into racing. heres a start for you



Did you look at the prices! Who in their right mind would want to start out and spend that kind of cash. Yes, speed cost money but that is just rediculious... and like any modified items, no warranty on anything. If you really want real speed start out with something that is almost there already, and improve on that. That's just my opinion. :ack:

05-13-08, 04:26 PM
ya skat just like your first post .as i have learned on myspace you cant read the sarcasm or emotions of what a person is typing and really meaning. i was being a smart ass and do apolagies if it was takin offensivly. i found it funny especially the coment about the harley stuff.

so ya your rite and i do understand your view. my ltz 400 quad im having the same prob i keep moding it out but i have surpassed the point where i could of just baught another LTR450.

and to the other fellow yes i agree after i saw the prices on these mods i sudenly felt that i am extremely pleased with my GTI as it sits.

have a great time have a drink on me:cheers: and thanks for your opinions

05-13-08, 05:06 PM
So cool John.....No apology needed..........I know I come across strong sometime. My wife says I have no sensitivity. Guess I say it as I see it. She no longer asks me how her butt looks in a new dress........:rofl:
I've been the route your talking about and that's why I made the post like I did. Like you, I've wasted a lot of money to mod, when I could have just purchased something faster............but you know what? The fun of tricking out what you have is what its all about!.........Like a hobby......it's just fun to do it..............:cheers:

robin savell lloyd
05-13-08, 07:13 PM
Great post everyone. This is why I like to come here as we can say it as we see it and in the the end we can agree or agree to disagree and everyone can still get along. Not all forums are this way you can see high school like minds in some of them more often than in here. :hurray:

05-14-08, 09:08 AM
The only difference I can see between the 130 HP and the 155 HP is the cam The throtalbody is the same unless it was a GTI rental {smaller} thay make three models of the GTI. rental .GTI .and GTI-SE so how much to buy a replacment cam for a 155 HP gti-SE from the dealer or have it reground to the same spec's it might be a lot cheaper than $1285.00 dollars. Just a thought.:)

05-14-08, 09:40 AM
Ok after looking at the spec's for the GTI family the cams are all the same same lobes and duration and the timming is the same the only difference is the wear ring the GTI-SE has a tighter clearence than the reantal and the 130 HP GTI -1021 the GTI-SE 0009 of a inch. the pumps are the same. So if every thing from timming to cam lobes to duration are the same were are thay getting the 25 extra HP it cant be the wear ring. The EMC must be giving it more fuel but every thing is the same except the rental has a smaller throttal boady. Im on a mission now.:rofl:

05-18-08, 02:15 PM
ya mods are more of a hobby for me. the challenge of buying the lesser model and building it to outrun the faster models for as cheap as possible. basicly boils down to rider abilety's (in motrcycle racing) in the long run.but i love going to the MX or drag strips and outrunning the natuarlly faster models.
ya my GTI so called rental model just trying to get it to pull thet dam viper 4 loaded with 4 heavy adults. have yall seen these viper 4's? theyre are a blast. once you get them to plain out .im gonna try to pull it again but with a difrent strategy .the SE has the standerd pull harnes .i installed a retractible ski pole.wich puts the rope higher causing more of a drag.so thus im gonna try putting the rope at the sam point as the stock harnes and then the next trick as the rider of the SE sugested is after the rope comes tight hammer it and dont let off till it plains out and everything launches. its quit a rush as everything is dragging then the seadoo slowly leans forward and the viper 4 lifts on top of the wake and sudenly everything takes of like coming to the top of a roller coaster. i highly recomend the viper 1,2,3,or4 seater rafts if your into extreme tubing stuff.easy to hold on to ,comfertable,hard to knock you out.and as weve seen at the lake even with 4 full size adults its size is big enough that if it catches a wake just rite it will send 4 peaple flying in the air .quit the site for shore goers.who were gathering at the shore to watch as we did our first time out's with it. serious fun