SeaDoo 657 Pipe Question

[Larry B]

Hi Bill,

I have been reading all these recent posts about pipes on 587s and 657s. My question is similar. I have a '94 SPX with the 657. I have heard that you can put the 657 pipe on a 587 and get some performance gains. Can the 717 pipe bolt onto a 657? If so, would there be any noticeable performance gains?

On a side note: I am considering swapping the 657 out for a 717 using the stock 657 electronics. My friend said that the 717 motors require more advancing than the 657 electronics offer. Is this true and if so, what might be the consequences of using the 657 electronics with a 717? Can the 657 pipes be used with the 717 in a swap or do the stock 717 pipes offer more performance. Guess I am asking because if I can put a 717 on my 657, I may do that as a first step in the conversion.

Thanks in advance,

Larry

[Bill O'Neal]

Larry,
You can use the 657 electronics on the 718 motor and it will work.

The high performance oem 657 pipe will work better on the 657 motor than will the 718 pipe.

[Larry B]

Thanks for the reply. From your answer, I will assume that the stock 717 pipe would work better then my stock 657 pipe on a 717 motor.

Is there any other parts, besides the motor/carbs and pipe that I would need for this swap? Will the stock waterbox from my 657 fit?

I know someone that took the stock carbs off his 97XP and may try to talk him out of them for the 717. These are slightly larger than what came on the 717 and I would hope they make a bit extra power.


Larry

[Bill O'Neal]

Larry,
Check out the bolt pattern of the 97XP carbs. They may be wider than the 720 pattern.I'm pretty sure (99%) they are wider.

Yes the 720 pipe will work better on the 720 than the 657 pipe will. Your waterbox will work though.

[cameron da river rat]

if you go to www.hlsm.com and take a look at the different year model sea doos you will notice the exhaust changes with other engines. as far as i know, there is little differance in the 657 and the 717 pipe. i currently have a 720 pipe on a 657 and found no increase in power. the pipe is off of a 96spx and looks identical to the 657 pipe except for the location of one coolant fitting. [img]tongue.gif[/img]

there was a different style exhaust on the 94xp, 95spx, 95gtx, 95xp w/720, and all hx models witch i think gives a seat of the pants differance in throttle response. they don't have a removable cone at the end like the others do. they have a fat chamber with a small head pipe with a metal coupling and brass seal ring in between the two. the guy at the local sea doo shop said it gives a little more bottom end but no more top end. thats the pipe i would run on a 657 or a 720 but would match a larger set of carbs on the 657 like the 657x engines had when they ran that pipe. :D

[ November 17, 2001: Message edited by: cameron ]</p>

[Larry B]

I checked out http://www.hlsm.com/ and it turns out that according to the part number they list, that the '95 XP 720 had the same pipe as the 94 XP 650. The 95 SPX pipe is not the same part numbers as the 94 XP as usually the SPX is the previous years XP.

Basically, it looks like if I can get a hold of a 95 XP 720 pipe, it should run as good or better than my stock 94 SPX pipe AND the pipe will work if I decide to do the swap and put in the 720.

Unless I can get my hands on a good, complete 650/720 Factory Pipe setup that will work on both motors too :D

[ December 10, 2001: Message edited by: Larry B ]</p>

[Bill O'Neal]

Larry,
I have both pipes, used and for sale right now.
I want $75.00 for the oem pipe and $400 for the FPP exhaust system with ecwi.

[Lenchmob]

Hey Bill, I have a factory pipe for my 95 xp. I have the water solenoid but I dont have the brain that controls it. Do you have one of those that you would sell separately? I was looking at the msd one to purchase. [img]graemlins/spit.gif[/img] [img]graemlins/buck.gif[/img]

[cameron da river rat]

lenchmob,
you have a 94spx, i have one too. the pipe will fit but i didn't see any performance gains. you have to remember the 657 you have is a regular 657. the 94xp had the 657x engine. which had a 720 exhaust like the 95xp720, and larger carbs too along with a double coil in the electrical box that my sea doo racing manual said "gives a better timing curve" or somthin like that. all in all it was matched with larger carbs and a different electrical system to make the larger exhaust come alive!

the factory pipe is your best performance gain for the 657. the 720 pipe isn't "in my tests" gonna give any noticable gain in speed/hp. even though i use a 720 pipe on my 657, it ran just the same. you have to remember all 720's don't run the same pipe either!!!! my 96spx has a pipe like the regular 657 you and i own.

just tryin ta help. :D

[Bill O'Neal]

Lenchmob,
Yes I believe I do. If not, I could get you a Micro Touch unit or an MSD unit, and sell it to you at our normal discount. To order call my shop at 626 914 9509 and ask for me.

[Larry B]

Cameron & Bill,

I was aware of the different carbs and the fact that the 657 is different than the 657x. I didn't know about the double-coil setup though in the 94xp. I realized that the carbs are different last year when I tried to install a R&D flame arrestor meant for a 94XP/95SPX on my 94SPX. Two-holes vs. three-holes.

My ski is actually not stock. It has a Westcoast head and revlimiter, solas SC-J impeller, top-laoder intake and a ride-plate. It peaks out at about 7100rpm, but on gps is just under 47mph. I think the intake may have scrubbed off a few mphs and I'm considering switching it to either the stock one or a something else. When my ski was new, it was as fast as our friends with 94XPs

I also have a friend that may part with a pair of stock carbs from his 97XP. Do you happen to know if these will bolt on to my intake? If not, would they bolt to a 720 intake that would fit on my 657?

Bill...I may be interested in that FPP, but can't make any commitments until after Christmas. Is it a complete setup ready to bolt on? There was a guy trying to sell one on ebay, but it was only the pipe.

[Bill O'Neal]

Larry,
I do not remember ever seeing two coils in any 1994 model Sea Doo's. News to me.
They did use a different coil though. It has a built in amplifier, and costs about twice as much as a coil without the amplifier.
If my memory is correct, the X motor had 38-40's, the carbs that were the predessor to the "I" series. They mounted differently than the 38's that are on your ski, and had a different bolt pattern for the arresstor box.
The 97XP carbs will not bolt up to your manifold, completely different setup. They are "I" series and much larger bore carbs with a wider bolt pattern. No, they will not fit the 720 manifold either. You really don't need that much carb anyway. Find a set of 657X carbs, complete with manifold and RV cover if you can. Surely someone has a setup like that lying around their garage collecting dust.
94 XP's go about 49 mph stock. Try that other grate, or the oem grate if speed is what you want. It is NORMAL to lose peak speed when using an aftermarket grate. Afterall, it's job is to "hookup" better, causing more drag through the water. With those model hulls, it's either hooked up and not porposing, or unhooked and porposing badly. I always found a ride plate extension to work well with those hulls.

[cameron da river rat]

i could be wrong about the extra coil but the 657x does have more wires going to the stator (what for i don't know, i don't own one), and the sea doo repair manual and racing manual refer to the higher output (whether it's double coil or not) ingnition system used w/the 657x engines and that is the ingnition system they refer to swaping out for the stock ingnition on the regular 587, 657, and 720 for a better timing curve or somthing. the repair manual electrical box breakdown shows two coils in the electrical box on the 657x engines.

like i said, i could be wrong but just from the way it shows in the books, there is some type of (hotter/better) ingnition in the 657x engines. but then again, the books aren't always right!! [img]/graemlins/cwm3.gif[/img]

sorry for the confusion.

[Bill O'Neal]

Cameron,
There are two exciter coils on the stator of the 657X motor, like on the 587 yellow motors. This is where you are getting confused. In fact, the magneto itself is the same on those two motors.
But there is only one coil in the grey box. No SD manual that I own has ever shown two coils in the grey box.

[SuperMAC]

More Carb Madness:

Hi all, I have a 94XP 657x.. I was given the ski seven months ago. The motor came in pieces in a box and was corroded beyond help. I bought a SBT motor and sent in my "core".

Anyway.. The carbs *looked* good on the outside(paint was intact and looked good), but when I tried to rebuild them, they were completely full of that white powerdy stuff. I sheared every screw inside. Nothing inside was salvagable. I had my new motor and needed carbs! yuck!

I bought some 96XP stock carbs and made them work.

YES, they will work, but you will have to do some surgery.

What is the same?
-The carb bodies have the same mounting holes.
That is the important thing.

What is different?
-the 94xp used 38-40, the 96 used 40-42
(the intake manifold mates perfectly to the 40mm throttle body, better so than the 38)

-The butterfly valve shafts. They are totally different. I removed them from the 38's carbs and inserted them into the 40's. I reused the butterfly from the the 40's I had to dremel the butterfly slot larger to accomidate the 2mm larger butterfly. (very simple)

-inner venturi is a larger size.. There is a number stamped on it. I can't remember what it said, but it is one integer larger. You will need to change jetting. I ended up with 75 low and 140 high. I have a 36cc westcoast head. You may want to go with a 142.5. I have a R&D scoop grate and a DG ride plate on my ski. I kept my stock airbox, stock prop. My top speed is GPS'd at 46mph at 6650-6600 RPM, but I don't porpoise even with the trim all the way up!

-mounting orientation is 90deg off. Don't worry with the new shafts, it will work. The carb bodies are the same.

Use all of the mounting brackets on the old 657x carbs and you are good to go!!!

Good luck!

Q: has anyone used 42-40's on a 720 motor, are the carb bodies different?