Nova 21 DD Head button ORing

[Samuel Hagan JR]

Anyone know what this O Ring is for. Has some issues today running and the motor ran hot and blew this ORing out. I didn’t have another one so I tried to make one fit. Didn’t work. I ran it without a O ring and it ran fine. What is it’s purpose? It’s not for the water jacket.

 

[Walt Barney]

If you would turn over the button you will find a small grove in it, the O ring goes in this grove and then on to the case there is no grove on the case it is held in place by the water jacket, if it is stretched out you can cut it then take a very small out of the ring then CA glue it back to gather the head bolts hold every thing in place. any questions call me 256-779-6472

Walt Barney

 

[Samuel Hagan JR]

Yeah I understand that. But what is the purpose of it?

 

[steve wood]

keeps dirt out. not needed in a boat

 

[Samuel Hagan JR]

Thanks.

 

[RonShaw]

keeps dirt out. not needed in a boat

Thanks.

Sam,
Steve is correct. This oring helps keep the dirt out when the engine is used on a car or buggy and ended up being a secondary purpose for its use. The primary purpose and reason for the design, was to help eliminate head button harmonic vibration. For this reason, I suggest customers keep it in place. This vibration over time can have an effect on performance and the metal-to-metal seal between the head button and top of the sleeve, thus lowering compression. Many high-end rc engine manufacturers have also adopted this method for their .12-.21 sized high rpm engines.

 

[Danny King]

I’m not sure how it blew out. It will swell and oversize with certain chemicals. But I’ve never not been able to get it back in.
it is under no outward Pressure. Only squeezed.
and as stated was for vibration and it does keep sand out in car and buggy apps.
The fact that rc boats run a lot less time then cars and buggies before their demise, I’m sure it wouldn’t matter if you left it out.
but it is there by design.

 

[Samuel Hagan JR]

Can you just buy the O Ring Ron Shaw?

 

[Samuel Hagan JR]

I’m not sure how it blew out. It will swell and oversize with certain chemicals. But I’ve never not been able to get it back in.
it is under no outward Pressure. Only squeezed.
and as stated was for vibration and it does keep sand out in car and buggy apps.
The fact that rc boats run a lot less time then cars and buggies before their demise, I’m sure it wouldn’t matter if you left it out.
but it is there by design.

Engine got hot on me and the ORing swelled out of the motor and broke.

 

[Danny King]

Ok. I don’t see how that happened either. I’m not saying it didn’t. I just don’t see it.
they are cheap. Just get a cpl.

 

[RonShaw]

Can you just buy the O Ring Ron Shaw?

Yes. Look at the parts listing page for your engine on the website and you will see the part number. Its probably a 29002.

https://www.novarossi.us/pages/novarossi-marine-engine-parts-listing