Yamaha Outboard

[Dave Tinney]

I have a 2003 Yamaha 60 hp 4 stroke outboard. When first started the water pumps fine, after a few minutes it starts to slow and then stops. Changed impeller, checked thermostat, flushed system, and checked for obstructions. No change. What else could be wrong?

[zenoahphobic]

I have a 2003 Yamaha 60 hp 4 stroke outboard. When first started the water pumps fine, after a few minutes it starts to slow and then stops. Changed impeller, checked thermostat, flushed system, and checked for obstructions. No change. What else could be wrong?

If you checked the thermostat as opening when hot, then as your engine is cold they are closed forcing more water out through the tell tale. As it opens more passages are opened and it may seem your water pump cannot provide that extra pressure. What causes this other than a faulty pump?

[Dave Tinney]

I tried it with the thermostat in and out same results.

[99yam40]

water pump sucking in air or exhaust,
did you change just the impeller or did you do a kit with cup and wear plate and all of the orings and gaskets.
plastic water pump housing also if it shows signes of melting?

[zenoahphobic]

I tried it with the thermostat in and out same results.

Yes, out is like fully open.
This doesn't rule out a weak pump.
It is very unlikely that you have a large hole letting this pressure escape (opposite condition to restriction) after the thermostat opens, as the engine actually runs.

[Dave Tinney]

Did the kit with every thing.

[99yam40]

Yamaha kit does not have the housing included with the kit.
did you inspect it?

Maybe you have a leak some where .
strange it has good flow at 1st and then stops,
is that true with stat out also?

[Dave Tinney]

The housing looks new, and yes it acts the same with the stat in or out.

[zenoahphobic]

The housing looks new, and yes it acts the same with the stat in or out.

Weird. I can only think that as the hose (fittings etc.) get warm they collapse and restrict the flow. Unlikely to open up again though! Check if there is any component is pressing, or if there is a possibility of a kink in the tube (kink can occur at hot and then springs back when cold).
Another unlikely reason is that the engine is getting too hot "vaporising " the water; but you will see steam let alone your engine shutting down.
So does the engine continue to run without overheating? Alarm?
I don't know of any obstruction substance that solidifies getting warm!!!
However things can expand when heated, or can expand from dry to wet! Any possibility you have a sponge or like material in their?
I'm done for know.

[99yam40]

seems I have read about exhaust gases getting into the system displacing the water before, but do not know where that would be if it is not at the dampener near the pump

[Dave Tinney]

Finally got back to working on my motor the other day. Found a piece of rubber in the fitting on the left side of the motor where the tell tale and the flush tube hook together. When the motor got warm the rubber became plyable and blocked off the port for the tell tale. I'd like to thank zenoahphobic and 99yam40 for the help.