Slight clanking noise on the rear of the motor

[kkalsch]

Hi
I have a 5.0 Bravo 3 and was winterizing the motor this Saturday-While the engine was running (idle) on the hose I noticed a slight clanking noise coming from the rear of the motor -when I raised the rpm's the noise went away -it is not a valve noise -you have to put your head to the back of the engine to hear it -could this noise be from the exhaust flappers with no back pressure? The flappers and u-joints are new 6 month ago
Thanks

 

[zbnutcase]

Re: Slight clanking noise on the rear of the motor

Very likely the flappers, especially if the noise is kinda random

 

[Fishermark]

Re: Slight clanking noise on the rear of the motor

Don pointed out a good thing to check recently in another post - the idea that the starter bendix may not be disengaging far enough and the flywheel lightly hitting it on occasion. Just something to check.

 

[TilliamWe]

Re: Slight clanking noise on the rear of the motor

It could be the flappers, but the new style flappers shouldn't rattle like the ones of years past. Maybe they do, but I though the new ones were entirely rubber, no steel inside of them? So they wouldn't rattle.

 

[familyguy]

Re: Slight clanking noise on the rear of the motor

Not sure if the sound is similar or not, but this is the thread Fishermark is refering to:
http://forums.iboats.com/showthread.php?t=450270

Is the sound irregular or regular (rhythmic)? Does it sound like metal on metal? Try and be as descriptive with the sound as possible. Were you the one that replaced the flappers? Any chance they were installed incorrectly?

 

[kkalsch]

Re: Slight clanking noise on the rear of the motor

Familyguy,
The sound is rhythmic ?but as soon as you raise the the rpm,s it goes away ?also I put my hand on the y pipe and felt a tap tap tap ?this is on the hose with muffs no back pressure ,I have not tried to listen for the sound when the boat is in the water. The boat is winterized but I am going to pull the starter ?did your noise go away after fixing the starter?
I did but the flappers in myself ?I was replacing the gimbal ring and had to remove the back of the exhaust to get to the transom and noticed they where gone
Thanks

 

[familyguy]

Re: Slight clanking noise on the rear of the motor

What year is your engine and about how many hours are on it?

Is the tempo of the rhythm at the same speed (RPM) as the engine? Is it louder on one side of your engine or the other? Exactly, what does it sound like? Is it possibly a pinging sound, a knock? Think of sounds we've all heard through our lives and pick one it most sounds like. Without a more descriptive mention of what it sounds like the list of things it could be is too great. Get a mechanics stethoscope and carefully listen to the part of the engine where it's loudest.

Did you mean to say you replaced the gimbal bearing or the gimbal ring? If you haven't replaced the gimbal bearing it could be that. Although a shot bearing screeches more than clanks.

 

[familyguy]

Re: Slight clanking noise on the rear of the motor

Sorry, forgot to mention I haven't taken the starter back to the dude that rebuilt it to say it's not working right after only year, what happened. I'm almost a 100% positive that sound will be gone when I reinstall it in February after I recommision the boat. Like I mentioned in the thread, the starter ring gear that meshes with the teeth on the flywheel slides up and down the pinion freely - no bueno, not supposed to do that - which allows it to repeatedly strike the flywheel (sounds like a chain hitting a flagpole in the wind).

 

[kkalsch]

Re: Slight clanking noise on the rear of the motor

The engine is a 2000 with 600 hrs on it -yes the gimbal ring -I had the whole thing apart last year and yes I replaced the gimbal bearing along with everything else involved -quite a little project! Bravo 3 are notorious for the gimbal ring to go bad (lot of play from side to side) anyway I am going to take your advise and buy a Mechanics Stethoscope and check it our this weekend -I might even pull the flappers off to see if that?s the noise
Thanks

 

[familyguy]

Re: Slight clanking noise on the rear of the motor

When installing the flappers it's critical to position the flap (valve) with the longest lip pointing down into the pipe, otherwise it won't work right, it will restrict exhaust flow, may cause the noise you're refering to, as well as negate their intended purpose (preventing water from backing up into your engine). A defective one will make a sound at a much slower tempo than engine RPM.

Good luck.

 

[kkalsch]

Re: Slight clanking noise on the rear of the motor

Ok I got off early from work today and bought a mechanics stethoscope and sure enough it?s the flappers ?they really can only go in one way or they would sticking up into the rubber tube,but they make noise and when you raise the rpm?s they are held open and the noise goes away
Happy Thanksgiving!

 

[makinc80]

Re: Slight clanking noise on the rear of the motor

water shutters, just had that problem! easy fix on my 3.0l