[cool1]

Hello All,
We are having issue's with 50H.P. F50TLRX, My Bro-In-Law, Hooked battery up backwards and pop'd fuse in the engine comp, Now we have No spark. We did get the repair manual, But NEED Help. Whats the best easiest way to trouble shoot and fix this?? many Thanks All. Bob.

[Yamajoe]

this motor may have 2 fuses

[cool1]

Where would it be, We have the manual and its not jumping out at us???

We shorted the battery on a 40 hour used Yam 50TLRX, Whats the best way to trouble shoot and fix this correctly. Thanks Bob.

The starter is cranking fine, we see fuel behind the glass of the fuel filter and there is no spark to the spark plugs...what should we test next?"

[douglloyd]

Do you have the kill switch tether installed?

[Yamajoe]

If the starter is cranking then your fuse is ok. you can find the fuse by tracing the positive (black) lead from battery to the starter relay, the blck lead from batt. sits on red lead on relay post next to a brwn lead ( brwn lead goes to nuetral switch) , trace the red lead from relay and you will locate the fuse.

As you don't have spark, what is the condition of the plugs, get a good plug and check for spark on all coils; check the white lead from CDI to the tether for shorts, this is a cutoff switch, is does get frayed or burnt and this will short, and will not give you spark. You have a neutral switch, the brown lead from the starter relay goes to the neutral switch, move the gear handle back and forth and back to neutral as check for spark.

a simple OHM tester will be useful to test for continuity etc.

[rodbolt]

if the starter cranks the engine quit chasing brown wires as the cranking circuits are working.
no sense in testing a working circuit.

this set up uses a basic CDI ignition.
without the harness diagram in front of me first isolate the white kill circuit wire. if its grounded or the keyswitch is damaged it will shut down the computer.
hooking the battery up backwards may blow the fuse for the rectifier but I cant think of why basic spark would be affected.
start by testing the pulser coil inputs to the CDI then test the output of the CDI with a peak reading meter or a DVM with a DVA adapter.
do a forum search for a home made spark tester.
if I make it to the shop today Ill try to look it up and check for 12V inputs to the CDI/computer.
I dont see a lot of the F50 motors so I dont memorize much but it does use a basic ADI/CDI system.