Reliability of 720 Engine

[dean thompson]

Just how reliable is the Seadoo 718 engine in late model skis (2000 - newer)? Can it come close to rivaling the Yami 700? About to buy and need some advice....

[Technical Support]

The seadoo 720 is pretty much the most reliable seadoo engine. They will easily go 500+ hours if taken care of.

[BORED40OVER]

I AGREE WITH THE YAMAHA 701 RELIABILITY. I HAD 2 GO 300 + HRS. AS FAR AS THE 718 SEADOO I HAVE 1 NOW WITH APPROX 173 HRS GOING STRONG, THE KEY IS GOOD MAINTAINCE. TAKE CARE OF THEM AND THEY WILL TREAT YOU RIGHT. JUST BE WARE OF THE SEADOO 951. NOT NEARLY AS RELIABLE IN THE LONG RUN. [img]smile.gif[/img]

[dean thompson]

Can you guide me to the critical steps on achieving 300+ hrs?

[BORED40OVER]

WELL IM SURE THERE ARE ALOT OF VARIABLES ON THIS ISSUE. I CAN ONLY SPEAK FROM MY PERSONAL EXPERIENCES. THE FIRST THING OBVIOUSLY IS KEEPING EVERYTHING TUNED AND RUNNING SMOOTH. THE OTHER THING THAT I THINK IS CRITICAL IS PRODUCTS USED. SUCH AS OIL AND FUEL. I PERSONALLY USE PENNZOIL 100% SYNTHETIC 2 CYCLE IN ALL MY SKIS. ALOT OF PEOPLE WILL LET THEIR SKIS SIT UP FOR MONTHS AND THE FUEL GOES BAD AND LOSES ALL OF ITS PROPERTIES AND BAD FUEL IS BAD FOR THESE. WILL CAUSE DETIONATION ALONG WITH SEVERAL OTHER PROBLEMS. ALSO PERIODIC ENGINE TESTING SUCH AS COMPRESSION AND CASE PRESSURE TEST WILL TELL YOU IF ANY PROBLEMS EXIST BEFORE THEY TURN INTO MAJOR ENGINE DAMAGE. PERSONALLY I CHECK MY COMPRESSION 1-2- TIMES A MONTH TO BE SURE EVERYTHING IS IN GOOD WORKING ORDER.I RIDE ABOUT 40-50 HRS A MONTH ALSO THE WAY A SKI IS RIDDEN WILL PLAY A LARGE ROLE IN HOW LONG A MOTOR WILL LAST. RIDE IT VERY HARD AND HIT THE REV LIMITER ALL DAY JUMP WAVES AND LOAD AND UNLOAD THE MOTOR ALL DAY AT HI RPM WILL OBVIOUSLY KILL A MOTOR ALOT QUICKER. PERSONALLY I RIDE PRETTY EASY MOST OF THE TIME BUT WHEN I REALLY WANT TO GET CRAZY I KNOW I CAN WITHOUT ANY PROBLEMS. KEEP THEM TUNED, FLUSH REGULARY, USE GOOD FUEL AND OIL AND BASIC MAINTAINCE ON BOTH MOTOR AND PUMP AND THEY SHOULD LAST A GOOD LONG WHILE. MY CURRENT SKIS INCLUDE 1998 YAMAHA GP 1200--- 1995 SEADOO XP 720---- 1984 KAWASAKI 550 STAND UP OLDIE BUT GOODIE AND MY SONS YAMAHA PRO VXR WITH A 701 IN IT. I HAVE OVER 150 HRS ON ALL THESE OVER 207 ON THE GP 1200. MY LAST SKI I SOLD WAS A YAMAHA WAVEVENTURE WITH 232 HRS AND RAN FINE. HOPE THIS HELPS A LITTLE AND GIVES YOU SOME IDEAS.

[Bill O'Neal]

And fog your motor when you have finished using it for the weekend.........

[BORED40OVER]

NOT A BAD IDEA

[cbeastwood]

Hey, Dean,

You didn't get rid of your 951 PWC did you? Were you able to work out the kinks?

- Craig

[dean thompson]

Hey Craig,

YEP - Traded the GSX-L and the 900 STX in on a brand new '03 GTI. Had to rebuild the engine in the GSX again .... after all that work ... too much for me. Good to hear from you Craig. Still learned a lot on the project, but time to cut my losses.

Dealer gave me some cash for my ski's on a double trailer to boot. It is really neat to see some of the design improvements since my GSX. The air intake system on the GTI is much improved over the GSX. Almost impossible (yea right) for water to enter intake.

DWT

[cbeastwood]

Man, sorry to hear about your bad luck with the GSX. I know you put TONS of work into it!

Do you have any leftover modification parts for the 951 engine?

Hope you enjoy your new ski!

- CBE

[dean thompson]

Craig,

Yes, I actually do. Several heads (one milled). Mag cover, starter bendix, asst gaskets, injection manifolds (oil), PTO, and some other stuff. Was going to put it on Ebay at some point. Thompsdw@hotmail.com ...........

[dhud64]

I'm glad I ran across this thread! I've been debating, over the purchase of my first ski. For those that havent read in another post my current choices are:
1)96 Seadoo GTX $3,000 very good shape, 122 hrs.
2)02 Yamaha XL700 $5950 w/ trailer out the door.
3)03 Seadoo GTI $5,500 w/ trailer out the door.

I've pretty much discounted the 96, even though I feel better in that price range. I was leaning towards the Yamaha, but it has no reverse. While the Doo has reverse and 5 more HP.

I keep hearing good things about the 720 motor, that is whats in the '03 GTI correct? What's the deal with the brass gear on metal..that I've read about? I'll have to say I'm leaning towards the Doo. I'm doing some more price checking before I make up my mind..

Oh yeah, somebody somewhere said the GTI is a fairly wet ride. I suppose thats compared to the Yamaha?

Thanks again for this post !!!

[ March 15, 2004, 09:32 PM: Message edited by: dhud64 ]

[cbeastwood]

I knew a guy with a '99 Yamaha XL - now even though that's the prior generation's hull, I thought it was underpowered, boring, and poor-handling compared to my '98 GTXL. Topped out about 44 mph. I think he was bored with it within 30 minutes of getting it.

I'd probably go with the GTI out of those 3 choices. But you can probably find an '01 - '03 GTXL for those prices if you look.

[Technical Support]

All Sea-Doo's except the 4-strokes and 951's use a rotary valve for the intake timing insted of reed valves. There is a 90 deg. shaft from the crank turning the valve. This is about the only really bad point of the 720 design.

There are a number of things that can take out the engine directly related to it: Debris can catch the valve, striping the brass drive gear. Water can groove the cover, and evenutally strip the brass gear. Although rare, you can have an internal failure of the tension spring or seal. And most often, you'll see the inner crank seals begin to leak after time, usually after sitting over storage. That means a new crank.

Not every 720 will have these problems, but they are problems the Yamaha can never have.

And as I answered you in your other thread (please dont' crosspost) I would take the GTi for the price and handling. Forget the '96 all together.