Inboard exhaust configuration

[Outrageous]

I have to start with what a GREAT SITE this is and how much great info has been shared by its members. I have owned several boats over the years most of which I have modified, restored, overpowered etc and just beat till they broke. Of them all the SeaCraft is what I have gone back to as they stand out above a lot of others for there sea keeping abilities. I am currently in the middle or hopefully beyond the middle of a 23 SF resto project.
I would greatly appreciate any help or input to configure the exhaust system as there was nothing to go by as I bought a hull, trailer and some parts but no engine or transmission. I have what I believe to be the original muffler (two 4" inlets and one 4" outlet) but was wondering what it had as original for exhaust manifolds and the height of the risers. My plan was to go with center rise manifolds and spacers 3" or maybe 6". I have a 4" heat exchanger I believe to be original Volvo and was hoping to be able to cool the exhaust system with fresh water if possible. I have not been able to find a cooling diagram for this setup (1974) any help locating a source for one would be appreciated. Power is a 350 w/ a 71c B&W transmission.
Thx to all that reply.

[aldo]

Hope this photo posts & helps......
I had a 74-or 75 cc inboard.
No longer own the boat

[aldo]

My boat originally had a 351 Ford engine & I later put a 350 MPI Marine Power engine in its place. No problems ever with water coming in the exhaust

[Outrageous]

Aldo thanks for the reply and picture. Do you know if there were 3" or 6" extensions between the manifolds and risers? Where did your boat end up?
still LI? Did you get the Regulator?

[deepsushi]

My exhaust setup on my inboard is identical to Aldo's setup. I probably have a 12 -14 inch total vertical drop from my exhaust elbow down to a crusader swivel that right angles into the hoses connected to the muffler intakes. Getting as much height here is important as the inboard boats exhaust is below water and actually pitches down towards the engine. Not an ideal exhaust setup from a engineering perspective but a natural consequence of putting an inboard motor in this hull.

[Miles Offshore]

I had 1.5" extension blocks in my previous motor and never had any issues. My new motor im running dry stack exhaust and with the center risers is quite high already and im not adding anything this time.

[Miles Offshore]

Another shot of the barr marine "dry stack"

[Outrageous]

Originally Posted by deepsushi

My exhaust setup on my inboard is identical to Aldo's setup. I probably have a 12 -14 inch total vertical drop from my exhaust elbow down to a crusader swivel that right angles into the hoses connected to the muffler intakes. Getting as much height here is important as the inboard boats exhaust is below water and actually pitches down towards the engine. Not an ideal exhaust setup from a engineering perspective but a natural consequence of putting an inboard motor in this hull.

I have to agree with you on the less than ideal engineering. Do you have any flaps or anything other than the exhaust guard on the transom? Did the muffler you installed have a drain plug on it. I was wondering about the water in it freezing over the winter.

[Outrageous]

Originally Posted by Miles Offshore

I had 1.5" extension blocks in my previous motor and never had any issues. My new motor im running dry stack exhaust and with the center risers is quite high already and im not adding anything this time.

Looking good! Is that a 350 or 383? are the ex manifolds fresh water cooled and the risers cooled with exit raw water? I thought about possibly going the dry stack as well but haven't decided on anything yet. Thanks for the pics..

[Miles Offshore]

Thanks its a 350 vortec, risers are saltwater and manifolds fresh.