Why does my jet ski cut out at full throttle?

Question

i own a 99 yamaha gp 1200 and since i've had it i've been having a serious problem w/ it. every time that you open it up it will run for a few seconds then it will cut out and drop to idle even w/ the throttle mashed...when it goes back to idle you have to pump the gas a few times to get it going again...only really seems to do this when its porpoising really bad. but that's pretty much all the time w/ this ski...i've put on a after market ride plate to try to help w/ this w/ little results. also i've cut out the center two bars on the intake grate as well w/ no luck keeping it in the water. is this a carb problem w/ the cuting out?? someone please help me so i don't spend another summer getting blown away by all the other skiis since i can only run at 3/4 throttle!!!!!

Answer 1

Sounds like a fuel starvation problem.  It could be carb. but some of the things you say seems to contradict that.  If possible rig a small fuel tank and connect it to the engine inlet.  If it runs fine, look elsewhere.

Answer 2

because the engine over heats

Answer 3

could be anything but sounds more like a fuel filter clog.

Answer 4

I'm not much of a jet ski guy, more of a dirtbike guy.  But, it would seem to me that jetskis sit for an extended period of time due to seasonal  use.  I would check the fuel first, if it smells like turpintine, and has a yellowish hue to it, drain and replace.  If that doesn't work check the jets in the carb they could be plugged from bad fuel or debri.

Answer 5

Yeah you definitely need to clean your carburetor if you have not done it yet and that sounds like a carb problem.  You need to adjust not the idle but running adjustment of the carb.  Find a repair manual maybe at a dealer store and adjust yourself or take it to a motor sports dealer.  your high end needs to be adjusted on the carburetor.  Nothing major actually it is typical that this will happen after a few years of running.  I would suggest not to do anything else until you get your carb adjusted.  Otherwise you are waisting your time and money.  In the link read about carb synchronization.  Good luck.