Engine cranks won't start.

Hello all
I have a 1999 90 HP 2 stroke. I took it out yesterday and after having a difficult time starting initially it finally turned over. During the rest of the day it was fine ran great, started right up first turn of the key for the morning. Then running at low idle looking for baitfish it sputtered and stalled out. It would not start! The engine cranks fine but I could not get ot to turn over. It recently (3weeks ago) received a tune-up. Including new spark plugs, carbs re-built, a new thermostat and heat sensor. When I got it home I re-charged the battery cleaned the plugs (which were a little damp with fuel but fine). Again engine cranks fine but will not turn over. Any Help or suggestions would be greatly appreciated.
Thanks
Dusty

[99yam40]

Check to see if it is getting spark to the plugs. Your kill switch may have come off.

[robert graham]

same motor as mine. are you pressing in the key when you crank the motor to activate the prime start? do you pump up primer bulb good and hard? check fuel tank pick-up check valve, primer bulb, fuel quick disconnect on front of motor, fuel filter, fuel pump. drain carbs to see what's in them, with drain plugs out, pump bulb to flush out float chambers/needle valves. turn/press key and touch top of prime start -should get hot/warm. Good Luck! Let us know how it goes...

[jb123]

check for bad diaphram in lp fuel pumps.

Thanks for all the help! I drained the carbs, cleaned the jets, changed the fuel. I then cleaned the plugs again. The battery was charged and I bypassed the kill switch...no luck again. I took it to my boat mechanic and it turns out that my stator was shot. He also said that there was a short somewhere in my wiring harness. Anyway we are changing the wiring harness, battery cables and stator. My question is Is this engine any good. This is my first Yamaha and *** a whole lot of problems . New starter,new relay, carbs rebuilt, and now stator. I may fix it and sell it, I'm just really fed up with it right now.

I was just about to suggest stator....yesterday replaced mine on a 1999 225hp....exact same symptoms....now it runs fine...but you should try staying with the engine....its 10 yrs old so it sounds like you replaced many of the items that would be going at about the age of your motor...

I did do the decarb procedure with seafoam, which seems to help the engine run smoother....

[jeffsrig]

I have been battling with similar issues, drove my boat out in the rain noticing when I got to the launch that my fuel cap was missing, I didn't figure that I had gotten too much water in the system so I tried to start it anyway and had no success not even a sputter. I took it home drained the fuel tank cleaned it out reinstalled, and was having issues starting it again. I did manage to get it started and ran it for a bit before taking it out to the lake where once again it wouldn't start. Took it home again, dissmantled the carbs (which suprisingly was very easy to do and there are some videos on youtube that are very helpful) they were very clean but I blew them out anyway with compressed air, checked the fuel pumps to make sure they were working properly, reinstalled the carbs, checked all the plugs for spark and it still wouldn't start. Then I noticed something....... when I pulled the choke the butterflies were not closing all the way and I pushed them closed with my finger and VOILA boat fired up like it was no bodies buisness.
And runs a lot smoother now probably from cleaning the carbs. I did a lot of research on a lot of different forums to find resolution to my problems and I am glad that I tackled the problem myself rather than taking it to a mechanic. So thanks guys I appreciate the insight. My kids might get to go tubing this week after all.

Jeff

[pappastratos]

check for bad diaphram in lp fuel pumps.

Does this model have a low pressure fuel pump ?

[bomberwd]

I had similar problems with my 86 115. The choke on the gear box would not work right after the engine was trimed up high for shallow water. I then tried the manual choke on the engine and it fired right up. Not sure what the high trim has to do with it but there is something in common with that and the choke on the gear box not working correctly.