454 going EFI O2 Spacers
 

I'm planning a retro mod on a '77 Century Arabian V-drive ski boat. The current exhaust are Hardin logs, and I plan to keep them as this isn't a big HP build. I plan to make a spacer at the red arrows in the photo. My question is since the sensor will be slightly out of direct stream if I go this route will I end up with tuning issues. Also if anyone is familiar with where the water jacket dumps water into the exhaust stream on this style exhaust I don't have them with me and I assume its where the blue arrows are in the attached.

Holley Sniper setup is what route I will probably go as far as the throttle body and their HyperSpark for the distributor/timing control.

Thanks,
Erniehttps://cimg1.ibsrv.net/gimg/www.off...f947eea96f.jpg
https://cimg2.ibsrv.net/gimg/www.off...3c8441326f.jpg

I can't speak to where the water dumps out in these manifolds, but I suspect it is in the vicinity of the blue arrows.

Your spacer as shown with the O2 sensor mounted at the highest point vertically should work just fine.

Keep in mind the spacer will displace the aft camel hump piece and any associated hardware attached aft so double check all fitment issues.

Agree except I was reading the AEM Innovate install information and it says to mount your sensor bung 10+ degrees up from horizontal. Supposedly if you mount it vertically the sensor gets burned up. And if you mount it horizontally it traps moisture. So if you have a choice go a little above flat. Mine is flat, I didn't see the instruction till my bung was already welded.
I can't tell you how it does. Installed it yesterday and only got a run on the muffs in the yard.
Love the Century classics. If I ever have some extra money for a Sunday boat it would be a Sliding top Coronado.

I would pressure test them before doing anything else. 43 years old plus usage is a long time for any part to last.

I do plan to pressure test. I pulled one of them apart yesterday and was surprised how good they look internally. I don't think they were original to the boat. There was some scale form the freshwater lakes in the hill country area, and that clogs exhaust fast.

A lot of people are scared of salt water boating, I have pulled apart a few fresh water motors and wasn't pleased with the internal blockage of water passages. At least (my) salt water boats are being cleaned after every outing. And now with all the evasive species in our lakes the fresh water ones should be also.

Thanks,
Ernie