I am on vacation and wish to activate the L mode on my 09 yamaha fx HO cruiser , how do I activate this from the remote?

try using a mold destroyer agent ( bleach, mold remover , chlorine etc from a hardware /paint shop)
spray it in , let it sit for a few minutes then hose it out
repeat in a few days as mold spores will regrow
talk with a boat shop for other ideas

Cylinder not firing. No spark, fouled plug, bad igniter?

Sounds like you have a bad stator. It may be producing enough spark to start the motor, but under a load (as in the water) it simply can not supply the amount of spark needed. Sometimes when a stator is tested on a ohms meter it may test good, but still be defective do to the load it will come in contact with when put in the water.

Broke wire, loose connection. Check to a good ground.

How old is the fuel? Ethanol causes major problems if left too long. You may need to empty the fuel and clean out the fuel system. Try changing the fuel filter and adding some seafoam to the fuel and running seafoam thru the fuel system. Hopoe this helps.

L stands for limp mode
it is a mode that the ECM selects to prevent serious damage to the engine ( from you lack of oil )
have the fault codes read then reset with the scan tool

what size batteries do the remotes take?

i have a 08 yamaha fx sho it keeps on freezing up in the water and dying of, i was almost 10 miles into the ocean and had to be towed by one of my fellow riders. whats causing this problem?

did you mean 900 cause 9000 is overrived and the engine may be blown

I have a Yamaha fx 1100 that starts real slowly the battery is fully charged but the bike sounds like its not got alot of power going to the starter can anyone help solve this also battery terminals are clean and not corroded