Hover over images below

Easy starting, smooth running 4 cyl. power. Needle bearings in Mercurys are uncaged, OMC motors use caged needles. Both styles work very well at high RPM.

One piece block, no removable cylinder head, standard for Mercury until the V-6 era.

Each bronze reed cage feeds two cylinders and serves as a main bearing as well. All other bearings are rollers and needles. Top and bottom mains on the crank are ball bearings, center main is needle.

Completed Restorations

Mercury Mark 58A

Completely restored 1959 Mercury Mark 58A, 45 hp, for Joe Clary of La. who restores old wooden boats. Both the powerhead and gear case were completely rebuilt. The motor started with the third pull of the rope.

Mercury

The 44 c.i. 45 hp Mark 58 was the top mid-range motor 1958-1960. It was considerably more powerful and faster than it's predecessor, the 39.6 c.i. 40 hp Mark 55. Joe set the NOA 40-50 c.i. class record at about 42.5 mph with a Mark 58A driving a porpoising 13' Allison from the front seat in 1960. The Mark 55 had trouble beating the 43.6 c.i. 40 hp Scott except on a very light boat, the Mrk 58 could blow away the Scott on any boat.

In 1961 the 50 hp Merc 500 was produced. It had the same powerhead as the Mark 58 but had exhaust tuning added. Running from the back seat the 45 would run 47 mph on the 13' Allison once the bottom was straightened and the porpoise was eliminated. The Merc 500 broke 50 mph on a 13' Allison in 1961, and ran almost as fast as the 70 hp Mark 78 on a 14' Allison.