Howdy.. New to marine engines but I'm a good mechanic.. (lol).. Just got an '87 4 Winns 'junk' boat and a spare motor.. (again..lol).. anyway.. My first 3.0L seized, so we took it apart.. spun rod bearings.. got a 1985 spare engine.. low hours but sat for 30 years.. took it down to the short block and gave it a good look see.. I think we can get this one running.. (Got the '87 head overhauled so that's back on this '85 short block engine, but to the point.. what's going on with these manifolds.. 2 years apart.. the '87 has 5 bolts.. (at least one parts list I found shows "5 bolts" req'd).. but the head.. (both heads actually) have 6 bolt holes.. when we took the '85 manifold off, , (4 bolts,& 2 studs), we found the 'last' 2 holes.. rear of manifold.. had the studs in the head..(?) (why there?) But the '87 manifold has only 5 holes (the next to last rearward hole doesn't exist, even tho' both the heads have 6 bolt holes... and the '87 manifold clearly shows a dead wall in this next to last hole location.. (Gasket has the hole, the manifold does not).. What the heck is going on here? Why did they eliminate this next to last hole between '85 and '87 and why is it a secret?.. (I'm guessing this hole is / was too close to the riser area and might be prone to cracking??).. AND why did I find the 2 'studs' in the '85 head next to each other.. at the 'rear' of the manifold. (I checked the depth of the holes and the 1st hole and the last hole are both a bit shallower than the rest. (the 2 studs I found on the '85 head have short [course] threads that go in to the head).. This would make sense for helping to install the manifold if the 2 studs were at opposite ends to help during the installation..(?).. This stuff drives me nuts.. (short trip for me..lol).. I haven't yet bought an engine overhaul manual.. so looking for that.. but any info is greatly appreciated. pic attached of the '87 manifold.. does the rust mean it's definitely cracked? We filled the water chamber to the top with lacquer thinner and let it sit for couple hours.. nothing.. no leaks to be found..?? (Note the next to last 'hole'i s just a rust spot.. no hole).
