I have a 75hp optimax that is running fine, BUT once the boat comes out of the hole and the exhaust port from the cowling gets air it is MUCH louder than normal. It sounds like removing baffels from a motorcycle exhaust. Sounds normal at idle.
Any ideas? Dave

The exhaust port I'm referring to would be the idle relief boot on the midsection.I've had the boat set up with the setback plate and new prop for a while now and only recently have I noticed the change in noise. I have also changed the prop out with the factory aluminum with the same results. Dave

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