'99 Sundancer with 300 mag 350's and V-drives. I have this "chirping" type noise coming from the exhaust. You can hear it inside the engine compartment as well as from the exhaust ports on the starboard engine. This started late last year. I noticed it when first starting the boat. The noise echoed and seemed to dissipate after the cooling water started flowing from the above water exhaust port. Now that the boat is on land, I can hear the noise from the lower exhaust port also. If I hold my hand over the lower port until water starts to flow from the smaller, upper port, the noise seems to come and go. I am guessing this is due to water flow being higher in the big muffler that both manifolds exhaust into. I have attached 2 videos with sound. I hope someone has dealt with this before. The mechanic at my Marina never heard a noise like this before, but he is kind of young. This noise does follow RPM's as well.
