Exhaust flapper 'tick'???
 

When my port motor is running at idle I have a "tick-tick-tick..." that is in unison with the speed of the motor. If I bring up the RPMs a little, it quiets then goes away. I have completely gone thru the valvetrain (valves/springs/lifters/etc.) and everything is kosher. Oil pressure is fine. I have used a stethescope, but still can't pin point where it is coming from.

I spoke with someone today who mentioned that the exhaust flappers located at the transom (that prevents water inversion) mounted inside the rubber tubes that the exhaust pipes insert into, can sometimes when they get older develop a ticking. They are the flappers that are hinged in the center, located just before the exhaust gasses pass into the Silent Thunder box. Has anyone ever heard of this, or experienced it to confirm that this may be what I have going on? I would love it to be something as simple as this!

My exhaust manifolds are off and I didn't have time today to get them on to run it and listen to see if it was coming from there.


Thanks for any help!

When I had this problem, I locked them open, by shoving a broom handle up the tailpipe to keep them open and prove it was the flappers, not the valves etc. and it was the flappers. If you have some sort of access to lock them open, and run the motor then do that.

Thanks man. Unfortunately I don't have any access to them once the exhaust manifolds are bolted on. If that is where it is coming from I will just live with it........and have peace of mind knowing it isn't something criticle.

Oh yeah, and rchevelle71, when yours started doing that, did they look any different.....was any rubber missing, etc.....???

It is probably the rubber gone around the flapper, happened to mine. It only takes about 20 min to remove the silent thunder box to inspect the flappers. One of mine even broke the metal. I run the clamp on flappers now, and no silent thunder. Hope this helps.

Sam

I had something like that and it cost me $$$

Care to elaborate..........??

I had an 88 242 630 HP, it had the flappers. you remove the rubber hose and they are atteched to the metal tips that go thriugh the transom to your silent thunder. not a big job but very important to have.

What kind of speed did you see with 630 HP in a 242?
Did that 242 come with a 7.4/454 2 bolt main and Bravo drive?

It was kind of a clink, tick. You could hear it at idle in neutral......it was something in the drive or coupler. I don't remember.....and usually say FIX IT. Sorry!

I didnt notice any difference, and by the way, I didnt mean I LEFT the broom handle up htere, it was just a test to make sure that is what it was bewfore removing them. I ended up replacing them with the Corsa muffler tips.

my 91 242ls ran 74 gps last weekend with four adults and 3/4 tank of fuel . with a mild comp blower cam and srp pistons with 7.5 lbs of boost on my standard bore 502. this combo with a little head work and some inconel valves should be around 600-650 hp . i can pass alot of boats on the water but not to many fuel stations !!

I had an ‘88 242 SS that I purchased new with a 330 HP 454 and a bravo drive. I added a blower to it, MSD ignition and Stainless Marine exhausts, modified the Silent Thunder Exhaust and a few little things that got me to upper 60’s.

After about 8 years instead of freshening up the engine I purchased a new 450 HP 502 crate motor. My wife thought I was nuts! I guess she still thinks that. I put into the new motor J&E blower pistons, new cam, roller rockers, pushrods, timing chain, new valves and valve job, replaced all of the lower end bolts, replaced the head bolts with studs had the blower rebuilt, put my Stainless Marine exhaust on and SCHAZAM!! I had a 630 HP upper 70’s MPH GPS boat. I also upgraded to the later model Bravo and IMCO hydraulic steering (you need this above 70 MPH). An old friend once told me there is no replacement for displacement, more is always better.

This was a great boat in the late 80’s and 90’s that used to kick a lot of but. There were not a lot of boats that went 70+ MPH. This boat was a real sleeper, it is a SUN and Sport and it all fit under that rear bench seat (1/2 inch to spare over the Holly carburetor float adjusting nut).

Always remember Eagles do not hunt flies!

I have a 1996 382 and I think I have too much back pressure on one engine, motor is weak above 4,000 rpm, I have checked everything else out, what is inside of the silent thunder ? Can a piece of fiberglass break loose or delaminate restricting flow ? Does anyone have a picture of the guts ?