Offshoreonly.com - Strange Engine Noise

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - Strange Engine Noise (https://www.offshoreonly.com/forums/general-q/251139-strange-engine-noise.html)

Exhaust flappers will make more noise on the hose than when the boat is in the water. There is much more water flow past them when the boat is in the water which quiets them some.

Quote:

Originally Posted by astar77350 (Post 3373362)

Hey guys,
Just started my boat today for the first time. Everything seems to be running fine but I'm getting a strange clicking sound from inside the engine compartment. It is not an enternal sound, as i used a mechanics stethascope and couldnt hear anything coming grom inside the engine itself. It seems to be coming from the very back around the drive shaft, and it sounds similar to a belt or something plastic hitting against something. I know this is very vague but any suggestions or thoughts would help.

I am a little confused with the focus on the exhaust flaps.....?

I have the "noisey" internal flaps in my system and when I first got the boat I heard the noise and was not sure what it was until explained to me....the noise does NOT sound like a "clicking" as described above and I would think would definatly be heard through a stethascope as used above...??

A clicking noise could be an electrical current arching..??

Not sure what engine this is but I believe most Mercruiser units have the coil and other electrical components towards the rear of the motor where the noise was described coming from?

I am guessing a loose wire or plug boot....:coolcowboy:

First off, yes the boat was on the trailer with a hose attached to it, and when i think about it, this was the first time I really ran it a while out of the water with the hatch open.

engine is a 454 mag, and yes the distributor and coil is located in the back. The click didnt have any sort of consistancy to it, just random, and as i tried reving the engine I didnt notice the sound speeding up (although it was harder to hear with the motor revving). If the sound was from an arching, wouldn't it speed up with the engine revs? I also didnt put the stethascope against the exhaust. Plan on putting the boat in the water this sunday, so i will be testing all these theories.

Also, I actually put the trim all the way down, so it could have been with the drive, but again, the noise didnt speed up with the engine... Ill keep you guys posted on my findings!

My SeaRay with thru-drive exhaust (Bravo 3) has the same issue- a random clicking caused by the exhaust flappers in the down pipe. Its just a minor irritation at idle when the engine hatch is raised- any other time you cannot hear it.

Internal exhaust flapper noise is not consistent and is as you describe. Also, the angle of the boat when its on trailer is different than when its in the water and that can angle change can make them rattle more.