Yamaha 90hp 4 stroke water flow problem

[dhubbca]

I recently purchased this 2007 motor. I have replaced the impeller and insert cup in the water pump. When I test ran it I got a decent flow through the pee hole with the ears on. At the ramp I started the motor and barely got a dribble. I pulled the boat and removed the lower unit and check the water pump and it all looked correct. Again reinstalled and with the ears good flow, at the ramp, nothing.
I have since also removed the thermostat housing, a new problem, and will replace the thermostat. Since I had flow through the pee hole when the ears were on however I don't believe that to be the real problem.
What and where can I look to find the block?

 

[DangarStu]

So it clearly isn't a blockage if the water pressure from the hose could push a good flow through. Given that there probably isn't much in the powerhead that needs looking at. Does much water come out from the thermostat housing if you take the cover off? Does the flow increase with RPM? As the tell tale is only a small percentage of the total water flow coming through the motor, it can take higher RPMs to get a good tell tale on some motors.

 

[dhubbca]

Since taking the thermostat cover off, I have not tried anything because I broke a bolt. Still haven't been able to remove the sheared bolt. Dealing with that before moving on. So far nothing has freed that bolt and it is looking like I might have to drill it out and tap it.

 

[alldodge]

Since taking the thermostat cover off, I have not tried anything because I broke a bolt. Still haven't been able to remove the sheared bolt. Dealing with that before moving on. So far nothing has freed that bolt and it is looking like I might have to drill it out and tap it.

:welcome: to iboats

To get the bolt out start with a sharp center punch and make a good punch mark in the center. Then go pick up a left handed twist drill.
http://www.amazon.com/Neiko-13-Piece.../dp/B000HS0UJQ

Put drill in reverse and start drilling into the stud, it should at some point start backing out. If you put a bit of heat on it before you start this can also help