2005 50 HP Yamaha Four Stroke will not go into high rpm's / full-throttle

[famas44]

I have a 2005 Yamaha f50 four stroke outboard with low hours. Went fishing a few days ago and put in five gallons of gas in a 15 gallon tank on the way to the lake.

The motor started fine and was full throttle for about 10 mins and received the "overheating buzzer / alarm." Motor went into safe mode... low rpm's after the alarm. Nursed boat back to the ramp and took it home. Installed new water pump and impeller. I have changed each year since I bought the motor in 2009. Also, a new thermostat was installed. Old thermostat was corroded. I have not changed that part in a few years. I tested the motor in the driveway with earmuffs and great water pressure throughout motor (weep hole) without any alarms.

My issue... went to the lake today and the motor started great without issue. Runs fine at low rpm's but noticed a little rougher than normal (thought it was bad gas). After I went passed half throttle the motor bogged down and would run rough. Tried for about half an hour to run the motor and it just will not go past half throttle or higher rpm's.

What is my next move? Should I change the spark plugs? If the motor did get hot, did it affect the spark plugs? I changed the gas filter, plugs, and oil in April without any issues throughout May. Does overheating cause bad pugs? I have done research and everyone is telling me fuel injectors or fuel issues. It could be those issues, but I am at a loss. ANY HELP IS WELCOME. Thank y'all in advance.

 

[99yam40]

Overheat alarm means you need to shut down the motor and let it cool off not keep running it.

could be a blown head gasket from overheat/ warping of head, getting water in a cylinder.
pull the plugs do a compression test or leak down test to make sure the cylinders are sealing properly.
inspect the plugs

 

[famas44]

Took boat out today and the same problem....do you suggest I look at fuel injectors? Bulb staying firm and no overheat alarm. Compression is fine. Plugs replaced...

 

[99yam40]

check spark on all cylinders
see if fuel pressure stays in spec
change screens and filters, and service injectors

 

[famas44]

Where can I find OEM fuel injectors to replace? I have looked on ebay without any luck...

 

[99yam40]

Yamaha dealer

but sending yours off to be serviced is a lot cheaper.
they will do as found testing, cleaning, and retesting so you know what or if there was a problem with them

 

[famas44]

I took off the injectors and filters are bad. Dirt poured out once dried. Do you know the size of filter? Also, do you know who is a good source to send them off to? Thank you for all your help!

 

[99yam40]

I would ask your local Yamaha dealer for a local shop name, or do a web search for someone close