Slight Tapping sound in V8 Mercruiser

[tk1891]

Hi, I noticed that when my engine warms up, I can hear a slight tapping sound. The engine is a 1989 305 V8 on a 20' Maxum. I was told by several folks who heard it that it sounded like a "lifter". Not being a mechanic I'm not sure how bad this could be. I was told as far as a possible easy solution would be to pour a bottle of "restore" in the oil fill and after a little running it may clear it up. Is this a common problem on Mercruisers (hell for that matter on any older motor I guess).

Also, to pour salt on the wound I discovered that the carb is gummed up which was causing it to flood quickly and the distributor cap was loose which was throwing the timing off. The excessive cranking drained the battery and killed the starter. I've looked around and noticed (depending on the carb) you can pick up a carb anywhere from $300-$1000. Is it better to just by a new 4 barrel carb or have mine rebuilt?

BTW - I recently purchased this boat and discovered this on the 1st trip out. Funny thing is, I was gone for 4 days and the boat ran great the 1st 2 days, on day 3 it went to hell in a hand basket.

Thanks for listening and advise!

 

[Philster]

Re: Slight Tapping sound in V8 Mercruiser

Does it go away when you rev 'er up?

At idle, exhaust flappers make the same sound and go away when revs build.

Oil additives cover things up very briefly. When you hear a real valve/lifter 'tap', revving it makes you cringe.

 

[itsneverfinished]

Re: Slight Tapping sound in V8 Mercruiser

an exhaust leak between the manifold and head will sound just like a lifter tapping.

if it is a tapping, however, just remember there is no fix in a bottle.

 

[dsiekman]

Re: Slight Tapping sound in V8 Mercruiser

I have a similar tapping in one of my Volvo 5.0's - 2000 with 175 hours. It only seems to happen at idle...or if it happens above idle I can't hear it! My last boat had a merc 7.4 and lost a flapper but it sounded more like a tin can banging around inside the engine.

If you do in fact have a bad flapper, the good news is you can fix it yourself and I don't remember it being very expensive. Actually, if I remember right, the new gaskets for the manifold/riser connection cost more than the flapper.

Good luck!

 

[tk1891]

Re: Slight Tapping sound in V8 Mercruiser

It does not go away when I rev it up. I was told that it sounds like a lifter. I purchased a new carb so I'll install that with the new starter. Then I've got timing to deal with as well, but I will check the lifters to see if any need adjusting.

Thanks for the help, any suggestions are appreciated

 

[tk1891]

Re: Slight Tapping sound in V8 Mercruiser

an exhaust leak between the manifold and head will sound just like a lifter tapping.

if it is a tapping, however, just remember there is no fix in a bottle.

Yeah, I figured it wouldn't be that easy, I'm checking the lifters next