troubleshooting...
I'm not to sure I'd invest a lot of money in this ski, till you find out if it's gonna be worth it.
I've been trying to access the wiring diagraphm, but I'm at work and our T-1 connection is really slow, must be heavy traffic.
I'd like to know about the wires you have dangling from your mpem. This seems that the other owner may have had some type of accessory that he was using. Take a voltage meter, touch the postive end to the red wire, then the ground of your probe to the engine block. Do you get a DC reading? You may need to have your lanyard plugged in for this. And if so, you'll only have 33 seconds to test before the relay shuts it off.
I wanted the wiring diagraphm to check the fuse you had missing. I wanted to know where it went to.
I think, because you don't know a lot about this ski, you should do a quick check of the crankshaft to make sure you have no real engine and bearing issues. Pull both the plugs out and lay them aside. At the back of the motor, there is a greyish shaft cover guard with 2 plastic wing nuts holding it on, remove that. Then, with the shaft exposed, see if the engine spins freely counterclockwise. Spin it at least 2 complete revolutions. If it turns over freely, without much resistance, then you can continue to work on the ski.
The battery. If you have bought a new battery and it went dead, you may have a short, draining your power. For the moment, un-plug the power supply to the VTS motor. The battery you bought, should have at least 200 CCA (cold cranking amps) or more. Anything less will probably not allow you to spin the motor past compression.
With that battery connected, you can hook it up to jumper cables of another 12 VDC vehicle, like your car, to try and start it. But you CANNOT have the motor running. You must never jump a ski/boat with another engine that is running.
Try and turn the engine over with the plugs removed. Put your plug wires on the grounding lugs. If the engine turns over well, with the plugs out, take one of your plugs and connect it to the plug wire. Then, lay that plug down on top of the engine. Then, turn the engine over again to see if you have spark at the plug. The lanyard has to be connected and you need two beeps to do this procedure. I'd do this in order before trying to start with your jumper.
Look to trouble shoot with the least amount of money until you know you have a viable base to work from. You may be wasting your money if you end up putting $1200 bucks in it, before you can get it to run. Let's make sure you got something to work with first.