OMC stringer replacement.

[Incredibad]

Boat is a 71 stamas 24ft with a chevy 350. The sterndrive was giving us some issues last year, get about a fuel miles out on a strait shot and it seemed like it would slip or drop into neutral and couldn't get her to move. let it sit for a while and she would be fine for a little before before doing the same thing. had the unit resealed as water was getting in. both the electric shift magnets/coils have been replaced. So while everything is apart and i have the money i was wanting to replace/upgrade the unit. the mechanic at the marina is young guy, and doenst know much about those old omc's like myself. he claims the unit that is on it now is a 68... a few questions i have, are, which model is this 400, 600, 800? and will going with a new unit, such as a a 78+ work? I see there are different year splits and what not. Im also finding it hard to find rebuilt units, any suggestions from anyone?

 

[Howard Sterndrive]

Re: OMC stringer replacement.

all OMC sterndrives from 1964 to 1977 were simply marketed as "The OMC Sterndrive" and were electric shift

at the factory, units were referenced by engine model e.g. "225", or by the 6 or 7 digit model number

I have never seen a reference for the latter... I wish I could stumble across some factory document that crosses the tag model numbers on drives to gear ratio and application...but cannot find anywhere

In 1978, "400" and "800" designations were introduced and assigned to 4 cylinder units (13 spline propshaft) and 6/8 cyl units (15 spline propshaft) respectively
the 400 and 800 carried over unofficially with the Cobra models. In 1990 it got confused when 3.0 4 cylinder units came with a 15 spline propshaft


So, the pertinent question about swapping:
Can you swap to a 1978-1985 800 series drive?

Maybe and sort of- IF your current drive is low profile.

All 400 and 800 series drives were low profile
many 1964-1977 units were high profile, which means a 400 or 800 series drive would be 4" too short- your prop would cavitate

So, find out if you have hi or lo profile first.. if lo, then it's somewhat possible to hang an 800 series on the trunnions - the ball gears will mesh
if you have the more common hi profile, then you are stuck with electric shift

1968 was a weird year. Do you have 4 or 5 bolts on the top cover of the drive?