Hit shallow sand water; now no or very weak telltale

[CaptainJS]

Hi good folks,

This weekend i hit a shallow water before I could get the engine up and the boat out again. Long story short, the engines telltale is very weak/or non existing. Sometimes it comes on and then its off again, irrespective of engine RPM.

I have been running the enigne 2 hours since then at different speeds (max 60% rpm), and monitoring the engine temp (gauge), which all looked very good (unless the gauge or sensor is at fault, but it turns on fine, and raises from 0 when I turn it on, so I assume its good). The little water that comes out is a bit hotter than luke-warm (I will say its around 120-130F), and I feel the top of the engine with my hand (without the cowling), next to the thermometer and it doesn´t seem super hot. When I run the engine off the water with the ears on, there is hot water comming out where the gear-selector goes in the lower gear unit (I hope you know what I mean). This tells me that the engine is somewhat being cooled, it just doesnt come out the right place.

I have checked the hose going from the top of the engine to the telltale, and no dirt is there (I can blow air fine all the way), so the stoppage is somewhere between the impeller and outlet. The question is what do I have to check, the impeller or around the thermostat? If I remove the thermostat cover, should one ALWAYS put a new gasket? Can one flush the engine the "opposite direction" to flush the stoppage out? What is your recommendation?

Many thanks.

 

[Lazy Daze]

It may not be a blockage - the sand can score the impeller wear plate and/or damage the impeller. Either of those can cause the exact problems you have. I would start by dropping the lower and checking that out. It only takes very minor scoring to loose water flow. When was the last time you changed the impeller and/or plate/housing? If you don't know... it's time!

 

[CaptainJS]

The impeller was changed on April 1st (this year), together with a major service. Thanks, thats also my thought, I will have a look at the impeller and plate/housing. However the fact that the engine is not overheating (at what degree F will the overheat alarm go on?), I suspect that the impeller is ok, but I will check...

 

[Lazy Daze]

A slightly worn plate or impeller doesn't automatically cause overheating. It's not a "black and white" issue - it can be a gradual thing. But the telltale, as you noticed, is a separate route than the engine - so limited water coming out of there points towards the impeller. Most OB's are like this, anyways - I'm assuming yours is - I'm not there to physically check, of course!

However, you can pop the t-stats out and check things out. If the cover comes off and the gasket is still good, you can reinstall. You won't really know if it will leak till you try... but gaskets are cheap. The next place to check would be the passages around the cylinders - pop the heads off.

 

[CaptainJS]

A slightly worn plate or impeller doesn't automatically cause overheating. It's not a "black and white" issue - it can be a gradual thing. But the telltale, as you noticed, is a separate route than the engine - so limited water coming out of there points towards the impeller. Most OB's are like this, anyways - I'm assuming yours is - I'm not there to physically check, of course!

However, you can pop the t-stats out and check things out. If the cover comes off and the gasket is still good, you can reinstall. You won't really know if it will leak till you try... but gaskets are cheap. The next place to check would be the passages around the cylinders - pop the heads off.

Ok thanks just to clarify: when you say plate, you mean the faceplate, right?

Which heads are you refering to, to pop the "heads off"?

Any possibility to flush this "backwards", when the lower gear and impeller is off?