Outboard Exhaust, Spitting water and Steam

[Captain PartyMarty]

Hi Guy's

Last time I was warming up my engines I notice that one of my outboards was steaming way more than the other one and it was spitting water out of the upper exhaust port. When I checked the engine temperatures the Steaming motor was running at 136F and the other engine was running at 156F. When we left the dock and got up on plane both engines ran at the same temperature 136F ish....

I am thinking the thermostat is stuck open on the steaming/spitting engine or could it be something else?

Engines are 200Hp Mercury Seapros.

 

[salmonkiller01]

Hi Guy's

Last time I was warming up my engines I notice that one of my outboards was steaming way more than the other one and it was spitting water out of the upper exhaust port. When I checked the engine temperatures the Steaming motor was running at 136F and the other engine was running at 156F. When we left the dock and got up on plane both engines ran at the same temperature 136F ish....

I am thinking the thermostat is stuck open on the steaming/spitting engine or could it be something else?

Engines are 200Hp Mercury Seapros.

Thermostat is my guess, you can pull them out and check that it is operating. Should be o-ring seal not gasket. I have had one get a small chunk of wood stuck in it and stay open.

 

[terrin]

Thermostat is my guess, you can pull them out and check that it is operating. Should be o-ring seal not gasket. I have had one get a small chunk of wood stuck in it and stay open.

Get a new thermostat and gasket and replace. Never a badidea to put in a new thermostat as they are fairly cheap. Doing that on my 9.9 New thermo + gasket, new impeller + gaskets and housing $100. Once your in there why not new.

 

[profisher]

Could be a stuck open pressure relief valve. The valve is spring loaded and dumps off excess pump water pressure during high rpms operation. It dumps from the mid section port on most outboards where you observed it.

 

[sly_karma]

Could be a stuck open pressure relief valve. The valve is spring loaded and dumps off excess pump water pressure during high rpms operation. It dumps from the mid section port on most outboards where you observed it.

Could be, but stats are usually easier to get at (I'm not familiar with Merc). Check stats first and eliminate that before going in deeper.

@Captain PartyMarty - do you have water pressure gauge or data for these motors? Are both motors in similar psi range at comparable rpm? - i.e., eliminate water pump issues if applicable.