Exhaust flapper valve replacement, 1990 Santego 3467

[BarryK]

Hi all,

The exhaust flapper valve on my starboard Crusader 454 is very noisy. It is inside the exhaust system somewhere, it is not on the exterior of the hull. Is it possible to replace this? Or is the clicking noise normal?

This engine is a Gen 5 454. The original Mark 4 was replaced under warranty early in the life of the boat. I'm not sure if the exhaust was modified or not.

My port engine had a top end overhaul a couple of years ago according to the prior owner. The mechanic changed the exhaust system and put in a large check valve instead of the standard flapper. The check valve only protects one bank of cylinders (the bank closest to the center of the boat). The exhaust from the other bank is directed at a 45 deg angle laterally instead of straight back to a 90 deg "T". The former mechanic told me that he worked with Crusader to come up with this mod. I'm not sure if this is acceptable or not. He left another 45 deg elbow and a large check valve to do the same mod to the starboard engine. I have not done this yet.

I've only owned the boat for a couple of months. Lot's of projects!



Thanks,
Barry

[bud37]

Why do you think the noise is from this flapper valve.......I would verify where the sound is coming from first, with the engine running listen to the exhaust all along the length with a piece of broom handle or a long screwdriver, that should give you the location ( may look like a fitting ).

Now , be careful while doing this.....

[Viper]

A check valve in that location on your port engine is a new one for me but hey I learn something new every day too. I'd like to know the logic behind that. You may not have a valve in the starboard engine exhaust. If you don't see anything obvious, look for a pair of clamps along the exhaust hose that seemingly have no business being there as there is no exhaust fitting present. Such would be the case if a resonator was installed in the hose. Having said that, it's a simple devise with no moving parts and would not cause the noise you describe.

I would consider what bud mentioned. This might be an engine or tranny noise. A tranny will chatter for example if certain engine runnability issues exist. Because of the close proximity, it's easy to mistaken this for an exhaust problem. Having said that, if there is a muffler close by, its baffle may have broken off and is tumbling around inside.

[BarryK]

Thanks!

I've got a mechanic's stethoscope which should work. I'll investigate.

The former mechanic used to work for Crusader I was told?? It has been a bit difficult to get information from him. I think the port engine got water in it which prompted the top end overhaul and the exhaust mod. He said the check valve protects the "inboard" head and the 45 elbow directs flow out of the "outboard" riser more efficiently; no room for a check valve on that side. The former owner did not get involved in the mechanical stuff. The mechanic said the noise on the starboard side was a flapper.

Both engines are running just fine despite the strange noise. They are V-drives so the engines are forward of the exhaust systems.

I have another noise on that engine from one of the accessory pulleys that I am also investigating.

[Cooler]

Not sure what your sound would be. I have a noise on my port side that is coming from the transmission. My mechanic advises that it is a somewhat "normal" situation that can't really be remedied. The sound is like a puck, puck, puck, when I start the cold engine. It goes away after 15 or 20 seconds, obviously due to a lubrication catch up. It does sound like it could be either the exhaust check valve or the outside exhaust flapper, but that is not the case with mine. My mechanic opines that some V drives make that sound, and some do not. Are your trannies Borg Warner Velvet Drives? er