Water flow issues ( from to little to too much)

[jason28]

Hello,
I have a 2012 9.8hp Tohatsu (MFS9.8A3) on a yacht on a mooring.
The water flow was very week or not coming out the tell tail at all during a short trip to give the motor a run a few days ago.
I had just replaced the impeller so I removed the thermostat and tested it in a hot cup of water and it opened up as it should. I reinstalled the thermostat and used a large syringe to pump hot fresh water back through the tell tail out let and started the engine.
Now the water is pissing out the tell tail at an incredible rate, way more than it ever has before even when the engine was new.
From my very limited knowledge I understand on some engines the tell tail is just a water take-off from the system and the remainder or the water circulates through the engine and out down through the leg.
I am concerned that I may have a blockage stopping some of the water flowing through the engine and out through the leg and instead forcing it all out the tell tail?
Hope I'm wrong?

 

[pvanv]

1. Never change only the impeller. Always do a complete WP kit. Same labor, pumps better, lasts longer, minimal additional parts cost.

2. The telltale only shows that the system is pressurized. It does not let a significant amount of water out. If it stops up, run the motor, and push a stiff wire into the telltale to free up whatever has it clogged.

3. Over 99% of the cooling water exits with the exhaust, and you don't see it. If concerned about an overheat, use an IR thermometer to see that the block is maybe 150F.

4. The thermostat has nothing whatsoever to do with the telltale.

 

[Sea Rider]

If wanting seeing a constant water flow peeing through water indicator poke a WD-40 red cannula back and forth several times with engine ON from time to time specially if the engine is constantly used in salt water.

Happy Boating

 

[jason28]

I appreciate the information gents,
Many thanks!

 

[MattFL]

Anecdotal data; I've got a 2014 model year Tohatsu 6HP that suddenly had a weaker than normal pee stream. I put a new impeller in and the issue remained. Oddly the area under the motor that usually gets very hot (exhaust) was very cool, even at full throttle. Next I replaced the thermostat, then the pee stream was very strong again and the area under the motor was getting hot again. So apparently the old thermostat was stuck open allowing so much water through that the cooling system pressure was lower than normal as shown by the weak pee stream, but thanks to the high water flow everything was staying cool, maybe too cool. Maybe your issue was the same?

 

[pvanv]

Anecdotal data; I've got a 2014 model year Tohatsu 6HP that suddenly had a weaker than normal pee stream. I put a new impeller in and the issue remained. Oddly the area under the motor that usually gets very hot (exhaust) was very cool, even at full throttle. Next I replaced the thermostat, then the pee stream was very strong again and the area under the motor was getting hot again. So apparently the old thermostat was stuck open allowing so much water through that the cooling system pressure was lower than normal as shown by the weak pee stream, but thanks to the high water flow everything was staying cool, maybe too cool. Maybe your issue was the same?

No. The pee stream is completely unrelated to the thermostat. It pees the same whether the stat is open or closed.

Yes, if the stat is stuck open, you will run too cool most of the time, and foul plugs. Again, never bother to just replace an impeller. If it needs a new impeller, it will best addressed by doing a complete wp kit. Same labor anyway.

If wondering about the stat, grab a $20 IR thermometer, and see if the power head is around 150F. If that is way off, it's time to check/change the stat.

 

[MattFL]

On this motor the pee stream does weaken due to pressure drop when the thermostat opens. You can see and feel the difference if you hold your hand back there while driving the boat. It's very obvious after a wide open run if you immediately pull back to idle. The thermostat will open due to the heat and the pressure drops, then as the motor cools off the pressure comes up. Every motor I've owned with a pee stream has behaved this way (50HP Honda, 6HP Tohatsu, 9.9 HP Mercury, 60HP Mariner).