What is this SeadDoo Mpep and dress key I am seeing some needing?

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cfauvel

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looking at some older PWC and some seadoos are requiring a MPEP...$1500+ new!?!?!?!
What I don't get is if the motors I'm looking at are 2-stroke carbed, where does a computer enter the equation?

What is this 'dress key" I keep seeing being sold with used ones?
 

Scott Danforth

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there are different DESS keys (not dress) that offer different performance levels. so you can have your teenaged kids use the jet ski and they have access to only about 60% of the power. it is also the security for the jetski

the MPEM is about $120
 

cfauvel

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Ahh you're right DESS key, whatever that means.

here is an example of the highly expensive new
https://www.ebay.com/itm/1997-Seado...ash=item2ccc99281d:g:nH0AAOSwdJ9aRBY2&vxp=mtr

and expensive used
https://www.ebay.com/itm/1997-Seado...ash=item441834fab8:g:2woAAOSwnsRaaz0~&vxp=mtr


it looks like there IS an aftermarket supplier of these too.
https://www.ebay.com/itm/SEADOO-NEW...w-JJaVABg:sc:USPSPriority!34243!US!-1&vxp=mtr


if I get a seadoo and I need one of these I'll DEFINITELY reach out to here first
 

Scott Danforth

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Ebay prices are 10-15 X real cost. go to a SeaDoo shop.

aftemarket MPEM's as low as $90 on jetskiparts
 

Scott Danforth

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I buy on craigslist to sell on Ebay. of the few parts I buy on ebay, they are NLA parts, and I usually offer less than 50% of the asking price.

Ebay prices are friggin crazy high
 

JimS123

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Ahh you're right DESS key, whatever that means.

DESS is "Digitally Encoded Security System". SeaDoo has had it on their 'Skis for eons and its clearly described in their Owner's manuals. Or, a 4 second Google will clearly describe it.
 

QBhoy

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Unless you are handy with your tools, I’d be tempted to stay away from older seadoo 2 strokes, with the exception of the older 700 odd cc engines. The 951’s have issues, of which I don’t have time to go into.
Great when working, but defo a constant reliability worry....as with most 2 strokes. The yamaha will be the most reliable of these and easy to work on come time for the enevitable 100hr top end rebuild.
 

JimS123

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The yamaha will be the most reliable of these and easy to work on come time for the enevitable 100hr top end rebuild.

Interesting comment. I have never owned a Yami 2-stroke but know several people that do. They all are late 1990's models and all have many hundreds of hours on the clock. Of course, all have been well maintained by ADULTS, and even though they have been run hard, they were all been put away dry (get my drift......LOL).
 

QBhoy

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Hi there. I have a 2002 yamaha GP800r. It’s a tremendous wee thing. Just that time told experience and preventative maintenance means a top end rebuild every 100hrs. Keeps them in great shape. Any yamaha 2 stroke racer or enthusiast will confirm this.
They are as reliable as these things get. Just need to keep on top of things. Power valve routine adjustment etc is another one to keep on top of too.
All the best.
 

QBhoy

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I’ll wager your friends skis with many hundreds of hours have at one stage had at least one top end rebuild. No doubt.
Worth mentioning about keeping oil injection lines in good order too, if not pre mixing @40/1
 

cfauvel

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Unless you are handy with your tools, I’d be tempted to stay away from older seadoo 2 strokes, with the exception of the older 700 odd cc engines. The 951’s have issues, of which I don’t have time to go into.
Great when working, but defo a constant reliability worry....as with most 2 strokes. The yamaha will be the most reliable of these and easy to work on come time for the enevitable 100hr top end rebuild.

I am very handy with my tools as I maintain a 32 year old evinrude 225, and a 49 year old mach1 Mustang.

a PWC will be new to me for sure. Trying to stay with either the yamaha engine that has 'jugs' or the rotax engine on the seadoos . How can I tell the 700 compared to the 951's?

is a 1996 Seadoo GTI one of the good ones? what about similar year SPX?
 

QBhoy

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Hi there.
Think the GTI might have a 700 series engine (think they 760cc) also the SP models mainly had this from memory. Don’t quote me, but usually a white engine and flat topped heads.
If you can, try and get a wee yamaha.
 

JimS123

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I’ll wager your friends skis with many hundreds of hours have at one stage had at least one top end rebuild. No doubt.
Worth mentioning about keeping oil injection lines in good order too, if not pre mixing @40/1

Actually, not. Of course they were adults that used them recreationally, and not "racers". And also this is fresh water use.

OTOH, I had 2 Seadoos of the same vintage, and they DID need rebuilding. That was always the source of the snide comments on the Lake - that their Yamis were still running with no serious problems and mine were always needing repairs.

Yeah oil injection is another issue. My Doo had problems there as well.
 

Brian 26

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I have some experience here, MPEMs on older two stroke seadoos are very expensive and very fragile, some are year and model specific so that will drive up the price. Yes there are used MPEMs that have a market value of $1,500, those are going to be for the twin engine jet boats. Yes you can buy some for as low as $90, those are going to be for the older smaller dime a dozen 600cc skis.

I've replaced two MPEMs, one in a jet boat for $700 I believe and one in a SPX 800 for $300ish. Both were used parts as that is only option for those year and models.

The dealers can not get MPEMs for older seadoos, the dealer by me could not even get parts for a 10 year old seadoo jet boat.

Another piece of info if anyone is interested: NEVER JUMP START AN OLD SEADOO, they all left the factory with a sticker stating such and this mainly because of these MPEM, the added current can destroy them.

I highly recommend West side powersports in MN and TX for older seadoos, they specialize in MPEMs
 

Brian 26

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How can I tell the 700 compared to the 951's?

is a 1996 Seadoo GTI one of the good ones? what about similar year SPX?

The 951s didn't' come out until 99 I believe, they are usually silver, they get a bad rap because when they do go they grenade and usually destroy the block. The 720 is kind of a dog (85 hp) the 787 motor is the one everyone wants.

This era of seadoo isn't really known for they're cruisers, the models that everyone likes are the sportier SPX and XP, they claim to be a two seater but are really just for one. I have a 97 SPX and really like it, these have a cult following and a lot of aftermarket and forum support.

As for reliabliity, you have to get one that is sorted out or do it yourself, there are a couple achilies heels that cause most of the failures, the biggest of which is the fuel lines, sounds crazy but they have to be changed or will cause the engine to seize.
 

cfauvel

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Thanks for the info "brian 26", that was very helpful. Alas I went with waverunners...but general information like this is great.
 

nacseo16

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DESS is "Digitally Encoded Security System". SeaDoo has had it on their 'Skis for eons and its clearly described in their Owner's manuals. Or, a 4 second Google will clearly describe it.


Great when working, but defo a constant reliability worry....as with most 2 strokes. The yamaha will be the most reliable of these and easy to work on come time for the enevitable 100hr top end rebuild.
 

nacseo16

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Interesting comment. I have never owned a Yami 2-stroke but know several people that do. They all are late 1990's models and all have many hundreds of hours on the clock. Of course, all have been well maintained by ADULTS, and even though they have been run hard, they were all been put away dry (get my drift......LOL).


Great when working, but defo a constant reliability worry....as with most 2 strokes. The yamaha will be the most reliable of these and easy to work on come time for the enevitable 100hr top end rebuild.
 

jbcurt00

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Great when working, but defo a constant reliability worry....as with most 2 strokes. The yamaha will be the most reliable of these and easy to work on come time for the enevitable 100hr top end rebuild.
Please obsserve the 90day inactivity rule

After 90 days w no new posts by whoever started a topic, consider the topic closed and for research only

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