Outboard Tell Tale Sign

Cooling is a very important part of the health of a boat engine.  Boat engines are put under much more stress than a car engine for many reasons, the most prevalent being that they only have one gear.  In a car, you may be doing 30 in second gear, on a boat you only have one gear, so its like driving a car in low for its whole life.  Running at such a high speed, the engine will very quickly produce one of the top engine killers, heat.  All of the parts in a boat engine are specially chosen to be able to handle all of the heat that it will produce.

 On a inboard, it can be difficult to tell if it is cooling correctly simply because it is just like a car engine, the only way to monitor whether the engine is getting enough water to cool is if you dont get any alarms or your gauge works properly.  

On the other hand, an outboard is very simple.  Some boaters will call it the "tell tale sign", the "sure fire sign", the "pee stream" or many other things that I dont think should be said on this blog.  :)  Every outboard has this in a different place, but I have yet to see one that doesn't have one.  

Some may produce more water than others.  Historically, Yamaha outboards have a very weak stream of water, when idling they may just look like they have a small leak, and even when up on plane, they will just have a very small amount of water come out.  I have not had any experience with the newer models as they may have changed this.  On the other hand, some engines have a very strong stream of water.  A charter boat that I used to crew on had twin Honda 150s.  These engines had a very strong and constant stream from the moment that they started to the time they got turned off.  

What to do in the even that there is a tell tale stream but there is no water flow.

If you are running your engine and the flow of water stops, there could be three possible problems.  In order from simplest to most difficult..... ALWAYS TURN OFF YOUR ENGINE AT THE FIRST SIGN OF NO TELL TALE STREAM.  

1. The hose has come loose.  The hose that produces the stream is just a rubber hose with two connections on each end, one on the block and one in the engine cowling.  Vibration can sometimes vibrate these hoses loose just leaving the hose pumping water inside the cowling under the engine.  No problem at all to fix, just reconnect the hose soak up any pooling water and you are ready to go.  There is not really any need to get every last bit of water as the heat from the engine will evaporate the remaining water.  Just be sure that water did not get onto any electronics such as the ECM or any electrical connections.  
2. The hose is clogged.  It is possible that there is some dirt in the hose from storage.  The easiest way is to use a paper clip or a piece of wire to unclog the hose.  Be careful though, the hose is made of rubber and you dont want to accidentally poke through the hose.  
3. Your water pump system has quit.  This is the most difficult thing to fix.  The most likely culprit is that your impeller has lost one or more fins.  This means you will need to replace your impeller in your lower unit.  When replacing an impeller, make sure that you have removed all the small chunks of rubber that where lost off of the impeller itself.  These can get caught in the engine and can cause even bigger problems.   

Here is a video of an older model Mercury and its tell tale stream.