yamaha 250 v76 no power

[discus420]

i have a 91 yamaha 250 v76 salwater series. it was running poor. i rebuilt all the carbs and cleaned all the jets. after repair still running the same. fires right up, idles fine, runs fine out of the water. as soon as its in the water and under load it will not run. i can idle around no problem but as soon as i give it gas or go wot it falls on its face and dies. i was thinking bad gas from sitting, so i put brand new 91 oct and it did the same. any ideas or tests i could perform? my next guess is i dont have enough spark under heavy load. im new to this motor and looking for any ideas or sugestions. any commom problems with this motor? thank for you time.

 

[bulletgwd]

Re: yamaha 250 v76 no power

had the same issue. test spark with a spark gap tester (autozone, etc, under $10) set the gap at 1/2 inch unplug all spark plugs except the one you're testing and crank motor for a few seconds. this will determine spark or fuel. my issue turned out to be a bad coil (found this by just switching coils). good luck!
make sure kill switch is on...

 

[discus420]

Re: yamaha 250 v76 no power

will just one coil cause this? i just replaced the stator. i now have better power and it wants to come out of the water but wont go abouve 1900 rpm. why would one coil cause this under load. there are five other carbs and coils . seems to me that they could make up the diference to at least get up on plain. again this is only under load. in neutral or out of the water there is no problem. i will check this out and see what i come up with. maybe there are a few bad coils. thanks for the advice