frustrating

[pete jurczyk]

Took my 1986 etlj 50 hp yamaha 2 stroke out to the ocean yesterday and it was running like a champ. All of a sudden it started running like poo misfiring and a bunch of other funky things. Almost felt like it was not firing on all cylinders.except if i would run it wide open, but it was a real pain to get it up to speed. It would either idle or run super fast and it only ran good at speed. So brought it home changed plugs fired it up and seemed to run great. Today took it back out fired right up ran great get out of harbor and gave it some throttle and the whole mess started again plus I could not shut it off with the key no more, changed plugs in the water ran great then same thing within 2 minutes. Quite frustrating to say the least and now Im clueless as to what to try next and why will it not shut off with key anymore? any help would be great and thanks alot

[99yam40]

check to make sure you alarm system works properly, it could be overheating and not giving the indicators that the alarm is happening,
But it would not run at high RPMs properly if overheat came in.

Probably carbs, but start with basics.
Compression, spark, and timing.
then fuel pump and carbs.

the wrong fuel to air ratio will not let it fire and burn the fuel mix properly
too rich or too lean

[pete jurczyk]

starter

Thanks for the reply I dont have a compresion tester but while going thru thing Ive uncovered alot of corroded wires on the starter sillinoid SPELL CHECK. Hopefully thats why it wont shut off with key. I use my boat 4 or 5 times a month and its always ran great and all of a sudden it started running bad. checked the carbs they look good jets were not clogged so Im kinda leaning towards a electrical problem, hope so or its going to the shop and Ill be broke plus I have spark fuel pump is squirtin fuel so whats next?