Yamaha alarm then intermittent bogging.

barefootin

Cadet
Joined
Mar 7, 2013
Messages
6
I have a 1996 Yamaha C75TLRU with oil mixed and I got an alarm buzzer today after a few minutes of WOT. After backing down and checking pee stream which was present but maybe not as strong as normal, the engine ran well for a bit then seemed to bog down or miss intermittently while at cruise (3500 rpm) on the 10 mile trip back to the ramp.
To describe the missing or hesitation, I originally misidentified the symptoms as the affects of wind gusts as there was no audible engine noise irregularities or drop in rpm. The motor did seem to be running a bit rougher than normal but could be do to running hot? I don't have much seat time with this setup and have been running 4 strokes for so long I don't really know what is normal for this rig besides the smoke and noise :).
I have a manual ordered but would like some feedback on my assumption that I am looking at a probable water pump / impellor replacement vs. fuel, carb or electric problems. Any help with troubleshooting would be appreciated.
Thanks,
 

99yam40

Fleet Admiral
Joined
Sep 7, 2008
Messages
8,851
Re: Yamaha alarm then intermittent bogging.

Test what you can to make sure those things are good or not and then look into the stuff you can not test.

Compression, spark, and timing are easy.
Fuel pump pressure/ vacuum is also.
Timing light should show if spark it going away if hooked up while running at higher RPM if you can keep it on with cowling off

Test you temp alarm to make sure it still works also.

Overheat can cause warped head and blow headgaskets letting water in cylinder, so ionspect the plugs and cylinders for any signs of water.

Most problems are fuel related, but since you overheated it could have something to do with it.
If you have no idea when the water pump and thermostat was replaced last then do it now, something caused the overheat
 
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