2000 Yamaha ox66 stalls at 1100 rpms

I have a 2000 Yamaha 150 Fuel Injected outboard (ox66) that stalls at low rpms. In the water it will not go above 1100 rpms in gear and 3000 out of gear. It cuts off immediatly but will restart right away once put in neutral.

History,
motor has had overheating buzzer sound intermittently at high rpms, reduce rpms and buzzer goes away. recently boat sat for a month without use when it generally gets used weekly. used boat last week and buzzer sounded again at low rpms. used *****ing motor to get back to dock. I removed the heads and found that the passages were clogged, cleaned and replaced heads. Buzzer still sounded when I turned the key on. Checked the engine oil reservoir and noticed that it was low. Found that the remote pump that pumps the oil from the remote tank to the engine reservoir wiring was bad. Replaced the pump and fixed the wiring(had to bypass the plug) and the buzzer went away. Took the boat out and I now have the current problem with stalling. Here is what I have checked so far,

Compression = good
Fuel pumps = good
Fuel Filer = good / clean (replaced)
Drained VST housing and gas was clean (replaced VST pump)
Cleaned and tested engine mounted tank sensor
Ran motor on external fuel tank with same results
All cylinders have spark
will not rev above 3000 rpms on hose with out sputtering and cutting out.

Could I have done anything that would have caused this when I fixed the following?

Cleaned and replaced head gaskets?
Re-wired remote oil tank pump by bypassing plug? (are there any resistors in the plug)


Any ideas that might help me out? Need to go fishing!!!!

kind of weird, but i just had the same problems. Turned out that the low oil sensor wire had come loose from the chipboard. Fixed that, could not figure out why it would stall out around 2k-3k rpms. Turned out to be a low pressure fuel pump.

Learned someting very good in the process from a well known yamaha mechanic. let the engine idle, squeeze the fuel ball, if the engine hesitates or stalls, probably the low pressure fuel pump. You are essentially flooding the engine if it stalls or hesitates.

[Tucker]

Now why would the engine hesitate or stall if you squeeze the bulb? The fuel level in the VST is con*****ed by a float valve? We need some smarter guys to chim in.

[boats.net]

If the diaphram in fuel pump is ruptured it will pump gas directly into crankcase and flood engine with gas, if it runs worse when pumping primer bulb fuel pump diaphram is ruptured. May also notice gas slick on water around outboard and fouled spark plugs.

[carpediemguy]

I agree fully. The rpm problem sounds like a fuel pump problem. My 250 OX did almost the exact same thing. There are 3 fuel pumps on the port side of the engine (silver). Fairly easy to replace and cost about $39 each. Don't forget to buy the gasket at the same time.

For the overheating problem, I've had a problem with the poppet valve. It's an easy inexpensive fix that may be the problem. It can get stuck open and dump out the cooling water. Hince, the overheating.

Hopefully that helps