my guess is a broken metal impeller piece inside of the WATER CIRC PUMP

I think BUP is hot on the trail. Was running a non-marine circ pump on my boat many years ago, and I started getting a weird noise from the front of the engine. When I pulled off the circ pump and took the back cover off, all that was left of the stamped steel impeller was a few little shards that were scraping the housing. Funny thing was that the boat wasn't running hot at all. The seawater pump moves enough water on its own that the circ pump is usually just along for the ride. Hell, I was probably saving a few HP not spinning the full impeller. :)

Nope, wasn't me - I was at Green River Lake this past weekend. I have a complete thread with a video somewhere on this forum. It makes a similar sound to what you hear coming from some of the high HP, high compression drag cars when they are idling at the starting line.

Check your exhaust manifold gaskets.

Omg !!! I blew up an impeller on the trailer at the end of last season trying to winterize . It came apart because of a chip in the housing. I wasn't sure I got all the pieces out and it seemed to run a tad warm . WTF ...

It does not matter if the WATER CIRC PUMP front of the engine is a marine unit because alot people who never pull that hose to drain the water out completely when winterizing can end up cracking and or breaking off the METAL PORTION of the impeller inside the water circ pump. Have seen it plenty of times from improper winterization or owners who do not winterize. Also saltwater kills these pumps down the road.

I am NOT talking about the rubber impeller for inside a water pump impelling housing - I am talking about the water circ pump on the front side of the engine. It is called an IMPELLER AS well, it is metal.

this view pic -

http://www.300cforums.com/forums/att...vents-pump.jpg

found exactly what I was looking for - Mercruiser broken internal IMPELLER - the exact failures I see - pic below they make that exact sound clank a clank

http://cdn.vanillaforums.com/ballofs...28449fa739.jpg

Post #5 :faint2::party-smiley-004:

http://www.offshoreonly.com/forums/g...ml#post4453774


Edit in: Oh, I get it. Same part, different issue. My bad.

[QUOTE=Budman II;4453993]Negro flywheel would be a lot larger, right? ;)

They are bigger from what people tell me, also they are cheaper to buy but much more expensive to own and performance is less than any other flywheel.