$400 for a non-running Seadoo with black mold? Why not!

May 1, 2023

On a random August day in 2022, I woke up scouring Facebook looking for something that peaked my interest. I had just sold the 1998 Honda CRV, so I had some money just burning a hole in my pocket. I ran across an ad for a 1996 Seadoo GTI for $1,200 (with a trailer) that did not currently run. I had always low-key wanted a cheap jet ski, so I made the decision to go check it out.

Upon arrival to look at the jet ski, I walked around it and inspected the hull which was very clean (no damage to speak of). The owner (guy in his mid-20's) came outside and explained that the jet ski was actually his grandfather's that he purchased brand new in 1996 and had never seen salt water. The battery was dead, so I couldn't test anything but I decided to make an offer of $400 for the non-running Seadoo with the trailer (figured the trailer with a title would be worth $400 itself). To my amazement, the seller accepted the offer. Here were the first pictures that I took of it in the garage.





So what is the first thing that I (a complete novice to the Seadoo world) decided to do once it was in the garage? Hook up jumper cables to it from my Lexus LX570 and try cranking it. What happened? I blew the MPEM (or ECU) and primary fuse going to the MPEM (which did NOT do its job of protecting the MPEM)... 



Turns out, you should always do research before doing anything on something you're not familiar with.. As the BatteriesPlus site says (and many forums/videos online):

"In the event you have a completely dead battery do NOT attempt to jump-start the battery with your car battery or even a jump pack. This can cause extensive damage to your jet ski's electrical system and is not recommended."

I finally decided to do some research and it turned out that the MPEM actually used the first iteration of Seadoo's DESS (Digitally Encoded Security System) system was actually reversible to a non-secured system with basic start/stop functionality. I decided to do this for simplicity sake as I didn't feel a $400 jet ski necessitated a security system (if someone really wants it that bad, they can have it).

My next purchases were a new battery, fuse, and MPEM. My grand total was about $100 because I used a Walmart lawn equipment battery and the aftermarket MPEM from eBay as shown below.


A week later, I spent about an hour taking out the MPEM box, replacing the MPEM, swapping out the battery, and fuses. Here was the outcome (spoiler alert, it didn't work):


I did some electrical testing to try and figure out what was wrong as I was just hearing a click, but no power to the starter seemingly. After tracing the current with a multimeter, I found that the starter solenoid (circled below) was not allowing electrical current through it (it was blown). I also double-checked this was the case by bypassing the solenoid with a 10-gauge wire (one post to the other) and the starter immediately engaged.


After all of the troubleshooting and work that I had done, it was time for another attempt...


Finally, signs of life... After a number of additional attempts, I was finally able to hold idle for a few seconds.


If you didn't know, 2-stroke engines emit a lot of smoke because they are burning oil and fuel, rather than modern vehicles which are 4-stroke. At the time I did not know the difference, however the testing of this engine really helped me to understand that both engineering-wise and first-person point of view-wise.


The following day, I decided that it was time for an inaugural run with the $400 (now about $500 total invested) jet ski. I hooked up the trailer, aired up the tires (never forget this step), got some Ethanol-free gas, and drove to the lake for the first time. 


To be honest, my expectations were extremely low. I figured I may be able to idle around the boat launch and when I hit throttle, I would just stall out. Needless to say, my expectations were exceeded...



I was able to take the Seadoo out for about an hour that day with no issues and running at WOT (wide-open throttle). To say that I was proud and shocked would be an understatement. For $500, I had a running Seadoo that I continued taking out for the remainder of the season...

until this happened about a month later...


My next post will go into troubleshooting the issue and cleaning to make this $400 jet ski actually look like something presentable

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