Ducati Outboard

Hi, have just got a 6hp? ducati outboard, it didnt seem to be pumping water, so I removed the leg to check the impeller. Problem is that there is no impeller there, thou there is a pipe that runs from the engine down to the bottom of the leg.There seems to have been some sort of brass fitting at the end of the pipe at the leg end (filter?) which looked to be damaged,which could impair the flow of water, if this is what this pipe does? I have searched the internet for info on these engines but there seems to be very little out there, so any info that anyone can give me would be appreciated. thanks.

 

Never even knew thay made outboards! Had a 250 single m/cycle way back in the mid 70s though, not too bad.

This link does list Impellors, trouble is it does not list the model No's of the motors. TBH if it was really old impellor it would have turned to dust and disintegrated. Make sure you have the keyway to fix it from rotating when you get a new one or maybe the shaft and impellor already have sufficient profile to stop spinning on the shaft. A flat on the shaft should indicate something, or a Woodruff key slot.

http://roadandrace.com.au/ducati_outboard.htm

Try e-mailing these guys, maybe they can help.

 

there is no sign of any impeller ever been fitted, the only shaft that turns is the one that drives the prop.

 

Maybe an air-cooled engine ?

 

ducati

was starting to think along those lines, maybe it is air cooled as there are fins around the engine, but I would still like to know what the metal tube from the engine to the bottom of the leg is for?

 

Some Japanese brands had air-cooled engines, maybe around 5 hp. Noisy, like most air-cooled engines. Not sure what the tube would be though.

 

Probably hybrid cooling like on an old Tomos. Exhaust gas enters the leg, causes the pressure to rise. The water level in the tube goes up and provides cooling to lower side of the engine. No pump, no impeller, utter simplicity!

 

ducati

Thanks all.

 

I'm puzzled about how that actually works.

 

Some motors, particularly very light ones, used water cooling just for the head. The block was air cooled. This worked because the max temp was at the top during tdc. Burt Rutan modified the Voyager's motors to run this way. As the piston expanded, temps dropped quickly. So a simple water gallery kept it from cooking. I haven't seen an OB like this, but it makes sense that a one or two cylinder motor could just use exhaust pulses to force water through. The bulge in the lift tube would house a check valve, I presume.

 

Turn the engine so the fitting is at the highest point and poor water into it. See where it goes or comes out. As the fitting is under water when operating, there should not be any chance of water damage

 

https://www.youtube.com/watch?v=ah-BhK3_FH0
ducati outboard video

 

ducati

Hi,thanks Barry for the you tube link, that is exactly the same engine as mine,so it is air cooled, so looks like I just refit the leg and give it a lick of paint. thanks again guys. great help.

 

All that fining is a pretty sure sign of air cooling......