I need some feedback on the appropriate side exhaust angle from the main fiberglass exhaust tube to the tube section that goes through the hull please. Here's what I'm dealing with:
Risers coming off the 454's have a 3" diameter.
Exhaust tube connected to the risers are actually 4" diameter Trident exhaust. Outboard side of the engine has two 4" 90 degree elbows and goes into a T-sweep. Inboard side of the engine has two 4" 90 degree elbows and a 45 degree elbow.
The T-sweep has two 4" inputs and a 5" output. I elected to use the T-sweep so I could put the exhaust up as close to the bulkhead behind the engines as possible per Bob Lico's comments about keeping the deck height the same when running the exhaust outside the outboard stringer to put fish boxes in the deck. This gives me the ability to easily convert to a 6" exhaust and muffler out of the engine for a diesel conversion.
Here's the T-sweep.
The Vernatube 5" exhaust is directly behind the T-sweep.
I have a 5" to 6" coupler behind the muffler that will connect to 6" fiberglass tube so the thru hull exhaust can be 6" and already set for diesel.
I'm not particularly concerned about exhaust back pressure on the 454's as the tightest point is the riser and I'm going into 4" exhaust tube now out of the riser instead of the 3.5" that was previously set up.
Where I am concerned about back pressure is at the elbow where the 6" exhaust exits the hull when there are diesel engines. I did some mock ups today using 6" plywood strips to better understand the exhaust angle and the size of hole that would need to be cut in the hull to accommodate different angles. Here are what those look like:
This is a 20 degree miter cut that leaves a 140 degree angle on the outside of the exhaust bend and creates a 8-3/4" wide faired exhaust hole in the hull.
This is a 25 degree miter cut that leaves a 130 degree angle on the outside of the exhaust bend and creates a 7-5/8" wide faired exhaust hole in the hull.
This is a 35 degree miter cut that leaves a 110 degree angle on the outside of the exhaust bend and creates a 6-1/8" wide faired exhaust hole in the hull.
This picture of the Super Mex restoration seems to indicate a fairly wide exhaust hole, which would indicate a more shallow angle around 140 degrees (based on eye-balling the width at 1.5 times the height).
Any feedback on what the miter angle of the exhaust tube cut or even the final outside angle of the exhaust bend out the side of the hull should be to prevent any back pressure issues would be greatly appreciated.
Thanks!
