Ox66 missing a gasket?

[Noble Savage]

I changed the impeller on my 175 ox66 two stroke and everything went well. But when I went to reattach the lower end, it looked like it might be missing an exhaust gasket with a kind of 6 sided shape. I ordered it based on the Yamaha schematics, but that one now appears to be higher up in the engine. So my question is whether there is supposed to be a gasket in this photo. I don’t think I lost it, but I wonder whether a previous mechanic did. I could imagine the engine working without it. Thanks in advance for the advice. Man I love scaring people flushing this beast in the parking lot!

 

[seasick]

On the 150SX there is no gasket. I suspect the 175 is the same.
Above that area in the midsection there is a rubber gasket that seals the muffler. That is probably the part you bought.

 

[Noble Savage]

thanks for the quick response. I think you’re right. There seems to be a rubber dam or seal between that cavity and the impeller housing area. The edge in question looks indented for a seal, but I don’t think it needs or came with one. Thanks again for the confirmation

 

[glacierbaze]

What is your water source, for flushing in the parking lot?

 

[Noble Savage]

Harbor has fresh water hose that I attach to rabbit ears and follow up with a longer run time at home using same rabbit ears. Do I need more

 

[seasick]

thanks for the quick response. I think you’re right. There seems to be a rubber dam or seal between that cavity and the impeller housing area. The edge in question looks indented for a seal, but I don’t think it needs or came with one. Thanks again for the confirmation

That rubber separator is a critical part. It is probably attached with adhesive and does not have to be routinely replaced. You may want to apply some marine sealant ( or RTV) to the top surface when you re-attach the lower unit
The rubber separator blocks exhaust gases and exhaust water from getting into the pump housing chambers

 

[Chessie246G]

what seasick said. Some people run a bead of high temp silicone sealer along the rubber separator. But a long as the rubber is in good shape its not needed. There is no gasket on the exhaust port.

 

[seasick]

Harbor has fresh water hose that I attach to rabbit ears and follow up with a longer run time at home using same rabbit ears. Do I need more

No

 

[seasick]

what seasick said. Some people run a bead of high temp silicone sealer along the rubber separator. But a long as the rubber is in good shape its not needed. There is no gasket on the exhaust port.

I should have mentioned the high temp requirement for the sealant.
Over time that separator gets hard and takes on the impression of the mating surface under the ventilation plate. When it gets like that, it may not seal as well as when new, hence the suggestion to dab a little high temp sealant.

 

[Noble Savage]

Thanks for the thorough advice, I think I will try some sealant just to be safe. I’ll also consider buying a replacement seal as a standby when I change the impeller next. It’s nice to service this stuff myself so I do it more regularly and know whether anything was suspect or not. The last mechanic pinched the thin gasket that seals the water pump housing.