Several weeks ago Betty and I were returning from a short cruise up the Seneca River and as we approached the dock there was smoke coming from the engine compartment along with the smell of hot rubber. We got to the dock and found the starboard side exhaust smoking hot with some of the boots ozzing melted rubber. Diagnosis found the starboard external water passage almost completely plugged, the port side was not as bad.
After getting the boat home I started the search for new manifolds and risers. Although the drive train is Mercruiser the exhaust is Volvo Penta as
I did thru hull exhaust when I repowered with the 351. The factory only offered log manifolds during the time they used Ford engines so I used VP center riser manifolds from a '96 boat. The manifolds worked well except the risers were so tall that I had to raise the front of the engine cover several inches to get enough clearance so the risers would not contact the cover. As long as I'm getting new manifolds I'll try to get something that fits under the stock cover.
Barr makes a small block Ford manifold for Indmar and PCM with the same short riser used on Mercruiser's GM applications. This combo lowers the overall height by 1 1/4 in.
These are the Barr manifolds and risers
The Barr risers are several inches shorter than the VP ones.
Here the Manifolds are installed. The height of the Barr manifolds are about 3/4 in. taller that the VP's.
Here is the finished install. The overall height allows the engine cover to be returned to it's original position.
All back together with good water flow.
Beyond correcting the water flow problem there are several positive changes. The Barr manifolds and risers allow the engine cover to be lowered to it's original position and because there are no external water passages sparkplug access is a breeze. With the VP manifolds the external water passages blocked sparkplug access. To get at the plugs the exhaust manifolds had to be removed. The only short coming of the Barr manifolds I see is that there are only 4 bolts per manifold instead of 8.
Overall I'd say this project is a success. One last thing to do is a test drive.