1998 Johnson 90 hp

[stprice]

While cruising in my boat the engine sound suddenly made an obvious change. It began sounding like a muffler with a hole in it. I have looked at the head gaskets and can find no obvious issues with them. Checked the lower exhaust housing and all looks fine. Any thoughts. Thanks

 

[joereeves]

Any work done to the engine recently... if so, what?

 

[stprice]

none on the engine. last work done was on the lower unit.

 

[joereeves]

The "engine" includes the lower unit. What you are referring to would be the powerhead which is another component of the engine.

I suspect that the seal on the exhaust tube that seals on the lower unit failed and is allowing the exhaust noise travel up the driveshaft tube via a failed or missing seal that sits on top of the water pump. That noise would then be blasting out the top motor mount area just under the front of the hood pan.