Friday I'll picking up my 98 seadoo GS. It's running but being an older bike I don't know how well previous owners maintenced it. What are some thing I need to change or service prior to taking it out on the water.
Also what Kind of supplies do I need to keep on hand. This will be my first jetski.
You need to make sure the fuel is good. Make sure the fuel lines are in good shape and have been changed. Not sure if the grey fuel lines were on your ski or not but if so they need to be changed. Oil and fuel filters would be a good idea since you don't know if they have been changed or not. Keep an extra set of spark plugs, tools to change them and a good supply of the correct oil on hand. Of course you need all the legal stuff like life vests and a whistle... things like that.
Congrats on your new bike. You should download a set of manuals (owners and service) They are available here on this forum under the manual section. There is a lot of info available in there on how to keep your bike alive. Read the recurring maint. section and follow through. Also you need to determine what fuel need to be used ie. premixed if the bike has been converted to premix or not. If it has not been converted find out from the previous owner(s) what type of oil was used ie. Mineral or synthetic. There are alot of articles on this forum reguarding what types of oil should be used.
These were just a few quick things, there are i'm sure many more and you'll probally be hearing from the more experianced members as I'm a newbee as well and have a lot to learn. This is a great place to obtain info and learn as there are many good folks here taking the time giving advice.