Hello, welcome to JustAnswer.
A good running WC starts on the water without having to do anything special. A WC that has idling issues for what ever reason often has no problem when it is on the trailer.
Boats run differently when they are not on the water. Usually they run much better. This is because when a boat is in the water there is a load on the motor just pushing the exhaust thru the water.
A jet boat (which is what a jet ski is, has a whole lot more load on it because they are always in gear, even in "neutral" that jet pump is pushing a lot of water.
So, a motor that is wore out, may sound and run great on the trailer, and not even start on the water. This is the reason that you should NEVER purchase a used boat that you can not test drive.
Jet ski's that are over 10 years old are very old as compared to a regular boat. If they are 15 years old I wouldn't look at them no matter how good the price is, and $1000 is not a good price. $500-$700 is all they are worth. for the 750.
There are a number of issues that could be the cause of the no start problem. Most likely is low compression.
I would take them to a shop to have them looked over and get an estimated of their condition. Honestly, they may not be worth the repair cost.
Had you asked before you purchased them I'd have advised you to walk away. For your first time you need something that is going to be more reliable than these.
Fuel delivery is one of the things that may be the problem. Using starter fluid will make it fire, I am sure of that. But that is not how to confirm a fuel delivery issue. Low compression or incorrect timing, or weak spark will also fire a motor when you squirt ether into it.
You may even be able to get it to keep running once you get it to fire. If that is cool with you (or you'd just like to ride the dang thing if you can) by all means, give her a go. Keep the ether with you in case it is required for a restart, and have some rope with you for towing purposes. (you should have rope even if the ski is brand new)
If you do get it to run some, when you are ready to get to working on it start first with a compression check. under 100 psi means it needs a new motor.
Of course it is possible to have the same thing wrong with two different motors. Who or where they were made has no bearing on them what-so-ever.
The motors need exactly the same thing to run. If they have it they run. period. If a motor has:
proper air/fuel mixture
correctly timed spark
Then the motor runs. There is no secret. If a motor doesn't run, one or more of those 3 things is incorrect. If it runs poorly, one of those things is incorrect. Finding out which and why is what the mechanic does. The more sensors and gadgets on a motor the more difficult locating the cause of the problem.
As for my not giving the other person the extra information. He didn't make a point of telling me he had no experience with his w/c. His no start was because his starter was not engaging the motor (no compression) He didn't sound like he could use a heads up about what might be ahead. And I didn't get a gut feeling he had just bought a worn out water craft.
If I gave the same answer to every question, that is when you should question my expertise.
I have told one person to take their boat to a dealer and another how to do it themselves and a third I asked if he thought he was up to doing it himself. All three had the exact same problem.
But since my going that extra little bit for you seems odd, and makes you uncomfortable, I will opt out and let one of the other equally knowledgeable experts help you with this problem.
Hello my name is Kenny, who am I speaking with ?
Are you still needing help with your Kawasaki Watercraft ?