Flushing an Elco EP-9.9 Electric Outboard Motor

A few years ago I decided to convert an old sailboat to electric power. After some thought, I decided that I could most easily install electric outboards, and after considering what was available I settled on the Elco EP-9.9 outboards.

Elco builds their outboards around standard outboard lowers, which has a number of advantages. Mostly in that they're compatible with pretty much every third party accessory. If it will fit on a Yamaha, it will fit on an Elco.

The big disadvantage is that the electric motor is up in the cowling, which means it has a drive shaft and gearing and needs to be actively cooled. So the Elco outboards have impellers.

The Elco user manual states that the oil should be changed and the cooling water passages flushed every 100 hours. and that the water pump be checked every 200. And if you're operating in salt water, you should flush the cooling passages after every use.

It provides instructions on changing the oil, but none on flushing the cooling water passages.

This may be old hat to those who are experienced with outboards, but it took me a little while to figure out how to do it, and I thought others might have a similar problem.

1. M8-1.25 Male x 8mm barbed hose fitting
2. 8mm ID hose
3. 14mm spring band hose clamp
4. 8mm barb x 3/4" GHT Female Garden Hose Adapter

There are three screws in the EP-9.9 lower. The one at the bottom is the oil drain, two above are labeled "WASH" and "LEVEL". Level (the one towards the front) is used in changing the oil. Wash (the one towards the rear) is the one you want for flushing.

You'll want to remove this. Use care, because the marina bottom is littered with dropped marine hardware. (Buying a couple replacement screws and gaskets before you lose them isn't a bad idea.)

You'll need to run a hose of some sort from your water source into the port that had been covered by the screw. It's a M8-1.25 metric thread. I bought a couple of M8-1.25 x 8mm barbed hose fittings. The screw into the port with no issue.

I found it easiest to screw in the fitting bare, then to install the hose and hose clamp afterwards, than to try to get the whole hose to rotate while threading it in.

I'm doing this in a slip, with dockside water, so the other end of my hose is a standard hose adapter. If your fresh water source is something different, you may need a different adapter.

With the hose connected, turn on the water. You should see water spraying out of the cooling water intake.

This is, if you think about it, flooding the area of the lower around the impeller. So go and run the motor. The prop should spin, and the impeller should spin, and the impeller should push water up through the water cooling passages, through the motor, and out the pee hole.

Make sure, of course, before you run the motor, that you're not going to cut anything or anybody with the prop.