what happens if your outboard does not get cooled?

[xschipper]

Hi There,

I have had a day with mixed emotions: after 5 years of restoring an old Danish runabout, I put the boat in the water. I have an old yamaha 55AE mounted which looks great.

Also in the first half hour, we had tremdous fun: the motor ran fine. However, after having some drinks and wanted to get going again , the motor failed to start. After some (20) tries, I asked my crew to see if there was any cooling going on. There was none. Finally the motor ran a bit, but still no cooling.

After one hour, a short try showed a direct start, but still no cooling so I stopped immediately.

If your read this course of affairs, is the failing of the cooling impeller a logical explanation for it?

Beste regards from a tropical Holland, Eric

 

[99yam40]

Re: what happens if your outboard does not get cooled?

water pump would be the 1st thing to look at, sounds like many years of just sitting around and impeller could be bad.

But if it was not pumping water while running for 1/2 hour the motor could have had some damage don the pistons and cylinders, check compression.

Could it be that your tell tail is just plugged and not showing water flow?

 

[Jlawsen]

Re: what happens if your outboard does not get cooled?

The question of what will happen if it looses cooling can only be answered in theory because the actual length of time operating without cooling is often unknown. Most common is "I shut it down as soon as I noticed it was overheating". How long was that? In your case it looks like it was about 20 minutes.

Damage is being done to some extent the minute the exhaust temp reaches about 1250 degrees. On most motors it's the upper cylinders that get the most damage. Two strokes will stop because of seized up rings or holes in the tops of pistons but it's actually fairly rare to find damage in the crank case. Two stroke pistons also swell when the get hot and scuff the sides of the cylinder walls. This makes it impossible for the rings to seat again. They also flash fire over the edge of the pistons which deposits carbon and aluminum into the ring lands preventing the rings from ever fully seating. That can result in a ring geting hung up in a port and breaking.

Here's the funny part, (if there is one), I've taken engines apart that were overheated multiple times over several years and the last overheat finally killed it. Sometimes they'll survive an overheat and keep running for years but there will always be some damage and loss of performance. Like I said, some folks just take it in stride, fix the cause and continue running for many years. The performance is sufferening but maybe it isn't enough to them to justify the cost of a complete rebuild. I hear a lot of guys say, it still runs so leave it alone.

Somehow, with all the work you've done on your boat, I don't think you're one of those that is willing to just run it into the ground.