So I've been fighting water in the exhaust. Some insight or help with situations people have seen would be very appreciated. Here's what I have as of now.
489, ported dart pro 1 310 rec ports, custom Jones racing Cam, stainless marine exhaust. If more details about the engine are needed, just ask.
First time I pressure tested the manifold with air and tested the trail pipes with acetone, both held air and acetone with no leaks visible. The tails are long and mix at the tips going through the transom. Today I just tested the manifold with 50lbs water pressure and heated them from the inside for 20 minutes, again lol leaks found. Double checked the tails again, same result. I started looking at the tips (pictures) and wondering if the jump at the top and the lip at the bottom is causing a swirl/reversion to occur? What I've noticed is the motor has a cylinder it 2 that miss until it clears the water as it warms up. Does anyone think these tips are causing the reversion or has anyone seen them cause it?



This is just a picture of the water laying in the bottom of the manifold.

Specs on the cam would be helpful

233/240 @.050"
.353"/.348" Lobe Lift
.600"/.591" Valve Lift
114 LSA

All the CAM specs provided.

Are you having this problem running off a hose or when in the water? Looking at the pic of the exhaust tips you don't have internal flaps? I see what could be mounting holes for an internal flap and then the lower lip is where the flap stops as water tries to make its way into the engine?

I'm sure it's off the hose after I flush it. There's no internal flap, just an external flat.

Looks like you have 3.5 degrees of overlap but that cam has alot of split for they LSA. That being said you always have reversion on the exhaust, even with a negative overlap cam based on the natural reversing of flow in the exhaust, yet more in the intake Port. The slightest of exhaust leaks can cause more reversion because it's inhaling air.

I come from the car world where header length helps with reversion. In a non water car exhaust it just dilutes your intake charge with exhaust.

Maybe try Nitrogen bottle with higher pressure to test. EGT gonna cause any crack to expand. I'm new to boats, but it's my new focus.

I did the Wallace racing calculator and that said I have 8.5 degrees of overlap "even worse" but what I think I'm coming to is making these tailpipes dry.

Generally, the Stainless Marine manifolds fail by leaking externally, vs into the ports.

What angle and drop are the tails from the riser apex?

Is the boat angled forward when on the trailer and run on the hose?

Bravo or TRS ?