2005 Yamaha 50 4 Stroke Poor Water Flow at Telltale

[JDusza]

Hi. Long time. Hope you're well.
Working on a 2005 Yamaha, model T50TLRD, serial 6C2L 1000653, that just dribbles water from the telltale. Flow improves with a pipe cleaner shoved up the telltale but you can only get up there 1 1/4" before hitting a T. One side of the T comes from the engine block, left side and if disconnected, water flows well from this port. The other side of the T runs from under the intake manifold coming down from the top of the engine, possibly fuel or ignition cooling? There is no water flow from this line. Seems there should be unless there's another thermostat type valve controlling this leg.
I have removed the thermostat to eliminate it from root causes. I have changed the water pump impeller.
These are my questions.
Should there be water flowing from the line underneath the manifold? That would "double" the output water at the telltale. Where does that line come from? Is there fuel cooling, air intake temperature moderation and / or ignition cooling on this engine?
I'm afraid that without water coming from the line under the manifold that I risk burning up the ignition.
I'm getting ready to work my way up the water line junctions. What should I be prepared to see? Any good Yamaha exploded part lists views out there?
Thank you,
J

 

[mike_i]

Did you recently change the impeller? If so did you do it because of the problem?

 

[99yam40]

have you tried blowing some compressed air up the tell tail while running motor on muffs or in the water to see it that moves things around out of the way to clear the passages?

 

[JDusza]

I have changed the impeller because of this problem resulting in no significant improvement.
I have yet to try compressed air. I plan on removing the intake manifold and tracing that water line upstream, junction by junction. I can use the compressed air along the way.
I found an exploded view of parts list and have determined that water is sourced from the top of the exhaust leg (presumably from the water pump) leading to the fuel injector pump leading out to the telltale.
I have a direction. Just got to get to it, now.
Thank you,
J

 

[99yam40]

Blowing a little compressed air up the TT is a lot easier to see if that helps before tearing things apart

 

[JDusza]

Watching the thermostat housing temp with an infrared thermometer I could predict when the alarm was going to blow; when I saw about 190 degrees.
I ended up splitting the T at the tell tale and blowing compressed air separately into each line.
On the power head side, air went all the way through the power head, down through the water pump and came out the water intakes. On the fuel pump cooler side, air went through the cooler and came out the exhaust leg above the water intakes.
Ran engine, watched temperature. It stayed about 160 with no alarm for a good 10 minutes.
Took the boat out to increase revs and generate heat. Ran it up to 2200 rpm for about 5 minutes. No alarms. Checked temp back at the dock and it was around 160.
Buttoned it back up and am ready to take it out again.
It appears blowing air displaced something inside somewhere.
Thanks for the help.
J

 

[mike_i]

Congrats on the repair, hopefully it works out for you and you can enjoy your boat until the next gremlin pops up.