1983/88 Mercury 115 Technical Questions

[Backmarker]

Good Day, my brother (mainly) and I have restored a 1966 Boat Locker "Malibu" The boat originally had a 1965 Mercury 1000 6 Cyl. Unfortunately we could not save the powerhead.

We opted to get an 80s model 6cyl with PTT, and the newer ignition system, in order to make it a bit more practical to use. After a year we managed to build a inline 6 with the 88 lower unit, PTT and gearbox, and an 83 Powerhead.
I have experience with OMC andthe Japanese brands, but 0 on Mercury and even less on inline 6s

here is a pic,with 66 decals on, contemplating if we must do the 66 engine coversand chrome beadings.

issue 1:

Cooling system
Engine running water is coming out of pee-hole AND a tube on the water jacket between the spark plugs

put a hose on it routed to the engine tray to prevent water from being sprayed over plugs
, what needs to happen here, and why is there an outlet on the water jacket?


Issue 2:

Motor starts, idles, a bit rough, and runs great for a few minutes, then it goes into a limp.

Action taken
Swopped out coil packs
New Sparkplugs
Sprayed a whole can of Quicksilver Power Tune to dicarbon
Cleaned Carbs
any ideas will be appreciated

here are some pics of the maiden voyage, after a 4year restoration project