yamaha ox66 water not reaching top of block

[WiltonGrady232]

This all started when the motor's overheat alarm came on while riding on the lake. I immediately shut that engine down and rode back to the dock on the starboard engine. Here's what it is doing now that I have it back home.

The engine is a yamaha ox66 and is pouring, not dripping water out the exhaust-- in a barrel of water, and when on the flush line. I have checked the poppit valve, thermostats, and the tell tale tube is clear. The problem is water is not reaching the top of the block.

I decided to do the easy first and the lower unit was removed and I replaced water pump (that turned out to not be the problem), and so I checked the water intake, and there is no blockages there. I also removed thermostats and poured water down the channels and it comes out the exhaust, no blockage there. I took the cover off of the poppit valve and held the valve closed while my wife forced water into the water channel with the lower unit off and it poured out of the exhaust channel. Is there a valve somewhere that I am missing? Or a seal that runs between the exhaust and water journal at the bottom of the block? I am at a loss and hoping someone with experience and knowledge can help me so I can get the boat back in the water.

What am I missing?

 

[dstarok]

On my 2002 hpdi the telltale water goes through the voltage regulator. It needed cleaning too as it can get clogged. That might be an issue.

 

[gw204]

Did you just pour water in the t-stat holes or did you force it in there? If there is a partial blockage, simply pouring might not do it. I would hold the hose nozzle as tight to the spot as I could and spray it full bore.

 

[WiltonGrady232]

I poured the water in, but it flowed out of the bottom of the motor freely. I did this on both sides of the engine. It doesn't seem like a blockage. With the lower unit off, I connected the water hose to the flush port and held the water intake tube closed with my hand, and the water poured out of the pee hole like it should and only a little came out of the exhaust port.

Where in the engine do the water intake and exhaust port cross? My thought is that it would be either corrosion and a hole there or a blown seal.

 

[seasick]

The more common issue is a bad water pump;impeller or housing. Since you changed that, it is probably not the cause.
There is a water tube from the LU to the powehead. It may be shot or disconnected.There is a bushing top and bottom of the tube. The seal on the drive shaft at the water pump could be bad too.

If you use muffs on land and open the t-stats to see if water is flowing, depending on the water pressure and volume, you may not see water coming out of the t-stat holes

When you got the overheat alarm, did you run it after it cooled off to see if it alarmed again? Sometimes you suck up a bag, or grass or sand and temporarily plug the inlet.

 

[Macksdad]

sounds to me like you possibly need to replace the impeller.

 

[WiltonGrady232]

Sorry for the delay guys. Today I finally got the parts in and pulled the heads. There was no buildup at all. I also pulled the water jacket plate behind the computer module and there was nothing blocking there either. So, I pulled the lower unit just to be sure everything was right with the impeller and it was.
I got everything back together and fired it up. Again, it didn't pee at all, but I did notice a bit of smoke pouring out of the pee hole. So, I pulled off on of the thermostats and fired the engine back up. The was exhaust pressure coming out of the main engine cavity hole(not the side with the thermostat).
Do I have a cracked exhaust port or could the main powerhead gasket be blown?

 

[WiltonGrady232]

I have an update. Today, after my frustration, I decided to do the ultimate test. I pulled the lower unit off of the starboard engine and put it on the port engine. Water flowed like it should. I have narrowed the entire problem down to the lower unit. I went over the new impeller again. I took everything apart and reinstalled it. I didn't see any issues. When I put it back on the engine, same problem. No water pumping.
When I installed the starboard impeller, it was very hard to put on. I had to tap it down the last few inches of the shaft. It was a snug fit. The port impeller slipped on very easily. I am guessing that the impeller and housing are not sealing properly to create the suction it needs. I am planning to just order another kit and install that. Maybe it's possible I got a defective set.

Thoughts?

 

[seasick]

I have an update. Today, after my frustration, I decided to do the ultimate test. I pulled the lower unit off of the starboard engine and put it on the port engine. Water flowed like it should. I have narrowed the entire problem down to the lower unit. I went over the new impeller again. I took everything apart and reinstalled it. I didn't see any issues. When I put it back on the engine, same problem. No water pumping.
When I installed the starboard impeller, it was very hard to put on. I had to tap it down the last few inches of the shaft. It was a snug fit. The port impeller slipped on very easily. I am guessing that the impeller and housing are not sealing properly to create the suction it needs. I am planning to just order another kit and install that. Maybe it's possible I got a defective set.

Thoughts?

It doesn't need suction per se. The tight impeller is not unusual either.
I don't remember if you said whether you had this problem just pop up or if it was after maintenance.
In any case, pull the lower unit and attach muffs to it. Run water and verify that water comes out of the output hole. Plug the hole and see if there is pressure if if water is leaking out somewhere else. Note that it is possible to install the impeller housing in the wrong position. You need to make sure that the bump out of the housing lines up with the water jacket hole in the wear plats and that the wear plate hole lines up with the casting. Also make sure there is a gasket where the LU slips onto the water tube.
One more thing: Some folks are certain that if the impeller is installed with the vanes pre-curved in the wrong direction, they will straighten out. I am not so sure and often wonder if installing the vanes in the wrong direction will cause damage to the impeller on start up. So if you are still at a loss, pull the pump apart and check that the impeller is intact ( by the way, broken impeller parts can block water passages)

 

[Andrew93]

The very first water pump I did on one of my first yamaha's I replaced the water pump and housing. I forgot to take the pickup tube gasket and retainer out of the old housing and put it on the new one. This caused an overheat similar to what you are experiencing.