9.9 to 15 conversion exhaust.

[Daveparm]

I recently converted a 9.9 to a 15 by changing out the carburetor, Reed valve spacers, and the tuned exhuust tube. I didn't change the exhaust housing.

Question is the new exhaust tube is about 1" shorter than the old and doesn't have the sealing surface on the gearcase side.

Now that it's all together, the exhaust seems to be escaping (bubling) out of the seam between exhaust housing and gearcase. When I place my hand behind the prop (emersed in water of course), it doesn't seem like I am getting full exhasut out of it.

Is this normal. It does appear that the exhaust housing part #is different between the 9.9&15. So to change to the tuned tube, do you need the matching housing?.

Thanks

 

[flyingscott]

The round tube does not have a seal and it does sit about an inch higher. Did you put the second copper tube in?

 

[Daveparm]

Thanks for tbe quick response. Are you referring to the copper tube that ends about halfway down the tube and sits next to it? If so then yes.

 

[Daveparm]

Just for clarification, the tube I'm reffering to is the same diameter as the water cooling tube.mounted to the opposite corner.

 

[flyingscott]

yes the shorter water tube. But it fits down the channel at the back of the exhaust housing. It runs past the exhaust relief ports.

 

[Daveparm]

Great, I am probably just paranoid. Testing today was done while running in a trash can. I'll get a chance to water test tomorrow. Being that it's not sealed to the bottom section, It probably is normal for some exhaust to escape at the lower unit connection.

 

[flyingscott]

Yes you are paranoid. What is happening is normal.

 

[Daveparm]

Yup I. Am.

.Water tested this morning, and it ran beautiful!

The only thing I would note for others doing this conversion is that because of the above, idle speeds are slightly louder. I boat at night often, and while flushing in a barrel, will be a little concerned of waking the neighbors on my late returns.