mounting engine for an omc drive

[boatman1963]

I am rebuilding a 1968 starcraft boat that had a merc 120 i/o in it that was totally shot. i am putting in a 1974 omc 140 and have a couple of questions as the sterdrives mount and sit differently to the engines. 1) when mounting the engine in the hull, should the engine crankshaft be parallel with the bottom of the boat or should the back of the engine be parallel to the transom? 2) been looking at pictures of omc transoms and would like to know how far out past the transom can the intermediate housing protrude? i know the ring on the housing should be centered in the transom opening but i think i am going to have to stretch some measurements to their extremes (where it will still work and be safe though). thanks!

 

[Boomyal]

Re: mounting engine for an omc drive

The OMC assy (intermediate and engine) have equal length mounting legs. The stringers they sit on are parallel to the keel. That being said, my '75 has an approximate 16? rearward slant on the transom. It appears that the top boot flange on the IH is lined up to the surface of the transom at the top of the boot hole. The bottom of the IH boot flange protrudes rearward of the transom, about 3". Hope this helps.

 

[boatman1963]

Re: mounting engine for an omc drive

thanks, that does help! now hopefully i can get it all calculated out to fit without having to fill in any opening from the old mercruiser opening in the transom. im pretty much starting my measurement based on the fact that the anti ventilation plate on the stern drive should be even with the lowest (deepest) part of the hull. the current opening in the transom is small enough that when i open it up for the omc boot, i wont have to modify anything unless i cant get my measurements to work out.

 

[Howard Sterndrive]

Re: mounting engine for an omc drive

are you really going to cut a Merc opening into a stringer boot sized opening? I can't imagine doing that to a boat...
So many stringer owners would kill to have the Merc cutout.
I would recommend using the OMC motor with the Merc drive or sourcing a Merc transom assembly rather than go to a stringer mount OMC.... that's hard to undo.

 

[boatman1963]

Re: mounting engine for an omc drive

someone gave me the boat nad it had been sitting outside for several years. the motor was junk, and the entire sterndrive assb was rotted, inside and out, otherwise i would be using it. i got the omc setup from a friend. was what i could afford.

 

[southkogs]

Re: mounting engine for an omc drive

A '74 OMC is going to be an electric shift - you're issue isn't the engine: it's the outdrive. There are some nice benefits to the Stringer drive, but the electric shift hasn't been made since the mid 70's and parts can be a challenge. Mercruiser is still in business and you can dig parts up much more easily.

If you can find a Mercruiser drive to mount that engine to, it'll save you MANY issues down the line. It'll also make it easier to convert later to a newer drive.

BEFORE you start cuttin' on the transom, I would STRONGLY encourage that you at least make sure the outdrive is working properly.

 

[boatman1963]

Re: mounting engine for an omc drive

some good points there. i think i am just going to park the project till the spring and maybe i will get lucky and find a mercruiser unit. i would prefer a mercruiser sterndrive. im always hunting for junk boats that people want hauled away so maybe i will find the right one. thanks for all the advice!!

 

[Bondo]

Re: mounting engine for an omc drive

some good points there. i think i am just going to park the project till the spring and maybe i will get lucky and find a mercruiser unit. i would prefer a mercruiser sterndrive. im always hunting for junk boats that people want hauled away so maybe i will find the right one. thanks for all the advice!!

Ayuh,... That's Good to hear,...

You were runnin' Backwards pretty fast there,...