My 1999 Yamaha XL1200 limited waverunner runs strong for about 15 minutes. During this time it has good throttle response and good speed (about 57mph), but after about 15 minutes it starts to bog down. It idles fine, but when you give it gas it starts to go, but immediatly loses power and bogs down. I have to creep back to the dock. It already has an exhaust temperature bypass module installed and I don't see any error displays on the instrument panel. Please help. Thanks!!
Hi, most likely cause and the easiest to check is exhaust leaking in the engine compartment. Run it without the seat fitted for the same time frame and if it fixes your problem you are looking for an exhaust leak. Regards Phil.
I'll try it, but when I run it on the trailer with the seat off I don't see any exhaust leaks. Although I don't usually run it for more than a couple of minutes. I've heard that there is a motor protection circuit ("limp mode") that limits the RPM if it thinks it is running too hot. If this is the problem I'm not sure why it doesn't show up on the display. I have a manual to check the water temp senor, but if that checks out good. I don't know what else to try. If you can think of anything else to try please let me know. Hopefully I can get out this weekend to try your seat suggestion. I'll let you know how it runs. Thanks for your help.
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SOURCE: I have a 2001 Yamaha
Several things can cause the problems you describe. 1) If there is a mouse nest in your waterbox, adding water to the nest plugs the exhaust causing the poor running. When it drys out on land it runs fine. Cleaning out the water box will not be easy on that model but a careful inspection of the exhaust outlet may tell if critters are the cause of your problems. 2) Corrosion in the teeter/totter needle inside the carburetor can also cause low power on the water. Try cleaning the carburetor. Warning: be very careful not to modify or stretch the spring on the teeter/totter. 3) Water in the electronics box can cause shorting and low power. Open the electronics box and inspect it for moisture. Leave it open over night to dry it out and put grease on the o-ring seal when reinstalling the cover. 4) One last possibility would be burnt or stripped screw on tops on the the spark plugs (if they are not solid top plugs), fouled spark plugs, or burnt out resisters in the in the spark plug caps. Replace the plugs ($3 each) and the spark plug resister caps($5-$8 each), make sure the screw on domes of the plugs are on tight. with any luck one of these checks should fix the problem you describe.
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