'78 Merc 900 Tower of power

So a coworker decided to sell his old Sea Ray last year because he didn't use it much and his daughter got accepted to a better college than he could afford. So last week he shows up at work with a barn find to replace it. Gift boat from distant relative - 78 Glastron with '78 Merc 900. Both have been tucked away in a garage for about the last 20 years and are cosmetically quite nice. As far as the Merc goes, the entire electrical harness has turned to dust, but other than that and basic stuff like water pump and fuel hose, we all have decent expectations for the thing. Another coworker is a trained OB mech, but this is a bit before his time.

Does anyone know of any parts houses or forums that are for this old motor? It's kind of a special block. It's an L5 with 3 carbs and the last distributor ignition Merc made. I suspect it is somewhat collectible, although the 140 hp variant is doubtless more so. Owner wants to get it running, but has no particular love of old machinery and would be happy to trade it off for something a little more modern and more easily maintained.

 

The alloy was the problem in these engines prior to 1984, it didn't much like salt water ! The 6 cyl 90 has many parts in common with the other "towers of power", so parts are around in quantity. Firstly check the engine for any internal rust, and compression. If any issues there, it is a doubtful proposition to be bothering with. And when i say check for compression, a good indication can be gained by just turning the flywheel manually to see if the six compressions per revolution feel even. The 90 was rather less thirsty that the higher HP variants, and had similar performance under sensible usage, though lacked the top end speed, not revving out as much.