I have a new 496 HO. Breaking it in. The sound of the engine varies...gets louder than quieter while the rpms do not change. Anyone now what is going on?

Stop moving around when you listen to it!

Seriously, any other details about the issue? What boat and exhaust are you running? Is it on the hose or in the water when this happens?

John

The exhaust is just straight thru transom with muffled tips, the kind with the spiral guts…It does it at cruise. I keep throttle in the same position. The rpms don’t change, it just gets louder, then goes away about every couple seconds. I’ts a subtle change in sound.

Might be surging cooling water momentarily adding more muffling effect. Never experienced this one before.

That's what I was thinking: surging of cooling water. However, if it is surging cooler water, it may not be getting enough. I'd make sure your impeller and water pressure are good. I know that my exhaust sounds very different before the water gets to the exhaust tips when running on the hose. Then it gets more muffled.

John

Thanks for the responses. Hope it's something normal, I'll keep monitoring it....No water pressure guage, but impellor brand new, firt time out....Under warranty (1 year) so we'll see.

Keep an eye on the engine temp...

I was thinking that the spiral guts in the exhaust tips might be too restrictve for the healthy impeller and the water could be building up in front of them. Be careful with this as it could cause some very damaging water intrusion.