Mercrusier Popping popcorn

[Elecmstr]

I have an '88 6.0 mercruiser with the alpha one outdrive. It sounds like a popping or clicking sound coming from the engine or outdrive. I have had the boat for a few months now and has done it since I bought it. It runs fine but I am not sure if it is something starting to go that I need to fix now. Thanks!

 

[vipzach]

Re: Mercrusier Popping popcorn

Does this increase/decrease when you turn or trim the drive?

 

[Elecmstr]

Re: Mercrusier Popping popcorn

I can only hear it at slow speds. It doesn't seem to change when I turn. I use the trim at higher speeds and I can't hear it then.

 

[elpaso]

Re: Mercrusier Popping popcorn

Do you only hear sound at idle or low rpm.?<br />Does sound stop after 1100 - 1200 rpm ?

 

[Elecmstr]

Re: Mercrusier Popping popcorn

It might stop at higher speeds but I can't hear it because of the engine noise.

 

[paulrfrancisco]

Re: Mercrusier Popping popcorn

is everyone thinking exhaust flappers... thing-a-me-jigs?

 

[elpaso]

Re: Mercrusier Popping popcorn

There are “water shutters” installed in your exhaust Y-pipe at rear<br />of engine. If a wave hit the rear of boat the 2 shutters will stop water from<br />coming up exhaust and flooding engine.<br />The shutters are coated. Due to age, this coating wears off. Shutter will<br />still work, but at low speeds will rattle against exhaust pipe.<br />This could be your sound.<br />Site below will show you exhaust system - check #6

 

[elpaso]

Re: Mercrusier Popping popcorn

I am having trouble posting this site.<br /><br /> http://www.mercruiserparts.com/Show...6.png&inbr=1014&bnbr=370&bdesc=EXHAUST+SYSTEM

 

[wdjohnston]

Re: Mercrusier Popping popcorn

hi guys, elpaso or vipzach i have the same thing going on with my 86 4winns merc 260 alpha 1. upon startup, there is a clanking sound coming from the stern area.it only does this at low r.p.m. and goes away after 1 or 2 minutes. elpaso suggested it is exhaust related {flaps?] the engine and outdrive run beautifully otherwise. is this something that should be fixed imediatly or can i finish the season then fix it .also, any idea what it would cost for this exhaust work.thanks w.j.

 

[paulrfrancisco]

Re: Mercrusier Popping popcorn

These shutters/flaps are there to stop a wave or a forceful reverse or a sudden stop from pushing water back up the exhaust into the manifolds and into the cylinders... That would be bad... Can you get buy for the rest of the season, the answer is yes, provided none of those events happen...

 

[elpaso]

Re: Mercrusier Popping popcorn

I know boats that the flappers, have been <br />rattling for 2-3 years.<br />Open the parts site above - print it -<br />You see the flapper is pinned, it the top of Y pipe. Start engine, at idle, if you hear noise,<br />place your hand where flapper is located, you<br />will feel it. Work quick, pipe will get warm.<br /><br />Flappers are easy to replace, if accessable.

 

[Elecmstr]

Re: Mercrusier Popping popcorn

Thanks for all the replies! I screwed up. I have a 5.0 not a 6.0 !!????

 

[scorpion264]

Re: Mercrusier Popping popcorn

I had the same problem come up this weekend in my 1981 260 mercruiser...Mine only happens when I drop it into gear. It almost sounds like or will remind one of a cylinder that is missing...however it is not related to the engine because it happens only while in gear and the clicking gets faster with rpm's to the point of a pur. This started after an extended distance at cruising speed. Any comments?

 

[crazy charlie]

Re: Mercrusier Popping popcorn

If you want to isolate the sound for sure then do as follows.Take a wooden broom stick and place it on the exhaust pipe where the rubber boot comes off of the riser and connects to the exhaust pipe.Now put the other end of the broom stick in your ear.Yes thats right,in your ear.You will clearly hear if thats where the sound is coming from.The wood acts like a stethescope(spell check please).If thats not where it is coming from then move the broom stick around until you can hear something.Charlie

 

[ziggy]

Re: Mercrusier Popping popcorn

i had a problem this summer that sounded like a popping or clicking noise too. i don't think this is yer problem as everyone seems to think flappers and seems more likely, but. i had made a real bad, dangerous mistake when routeing a new main power wire from my batt. to the starter. i didn't get the wire tied up so good. it got loose and fell down on top of the coupler area where the drive shaft spins. needless to say it didn't take long for the insulation to get damaged, then arc welding was takeing place at the coupler area via my main power wire. i hope this isn't yer problem. but it did sound just like you discribe, clicking and popping. i hate to even admit that i did that. as i surely had air and spark. all i needed was the fumes for an explosion. i was real lucky.....ya might just check and make sure ya don't have a wire arcing somewhere. live and learn. at least this time i did............along with charlie's idea, i use a couple of feet of heater hose. workes the same as the broomstick. a hearing hose.

 

[olbuddyjack]

Re: Mercrusier Popping popcorn

Originally posted by ziggystardust:<br /> along with charlie's idea, i use a couple of feet of heater hose. workes the same as the broomstick. a hearing hose.

A long screwdriver will work too. Sometimes they're easier to find when your fixin stuff.

 

[jpower9]

Re: Mercrusier Popping popcorn

My Mercruiser is also "popping popcorn." I have a 1992 Bayliner with a 4.6L V6 Bravo II. I was out with some friends this last weekend and took some turns rather fast. When I put the boat up it sounded fine. The next day when I took it out the outdrive was popping. It sounds like it's popping at all speeds. Does this sound like an exhaust flap? If so, someone please point me in the right direction. Is the exhaust flap in the engine compartment or on the outside of the boat. I have a service manual for my boat and am somewhat of a novice mechanic. Please advise! Thanks!

 

[Haut Medoc]

Re: Mercrusier Popping popcorn

Welcome to iboats......
Your exhaust shutters are located in the Y pipe under the "elbows"......​

 

[jpower9]

Re: Mercrusier Popping popcorn

Does the "y" pipe go under the engine? When I stick the broomstick in, am I doing it from the back of the boat on the outside near the outdrive or from the engine compartment? Sorry, I'm a little new to boating.

 

[Haut Medoc]

Re: Mercrusier Popping popcorn

It is at the back of the engine below the elbows......
You will need to remove the drive to see if you have a stuck/broken shutter......
Or, you could pull the elbows & see if the shutters are still in place....​