Engine Swap 1979OMC with 3.0L Quicksilver

[M0bi0us0ne]

I have an old wooden boat with a 1979 OMC 3.0L and an equally old OMC Stringer 400. In recent years, both the engine and the sterndrive have given me a ton of issues, and it is becoming exceedingly difficult and expensive to find replacement parts where I live (Italy). I'm usually able to find only overpriced, beat-up used parts, or I'm forced to order them from the US, spending a ton in shipping and import duties.
I just put the boat in the water, and the engine has started giving me issues again! Re-engine the boat with a completely new engine and sterndrive will cost me upwards of 20K (euros), and it will take months as the transom will need to be rebuilt. I was looking at the 3.0L Quicksilver 8M0116646 and wondering if it is compatible with my sterndrive. My understanding is that my engine is the "grandfather" of the Quicksilver. This will allow me to "just" swap the engines without having to rebuild the transom. I will eventually upgrade my sterndrive as well, but I can't afford it right now. If that engine is not compatible does anyone have any other idea?

Thanks

 

[dubs283]

The only sterndrive setup compatible with your current transom is an omc sterndrive colloquially known as a stringer drive

If you choose a mercruiser package you'll definitely need to rebuild the boat transom prior to install along with cutting, fitting, complete package install with new wiring and controls

Bringing your current setup to original spec vs refitting the power package to a new(ish) mercruiser 3.0L alpha setup is imo six of one, half a dozen of the other financially

 

[M0bi0us0ne]

The only sterndrive setup compatible with your current transom is an omc sterndrive colloquially known as a stringer drive

If you choose a mercruiser package you'll definitely need to rebuild the boat transom prior to install along with cutting, fitting, complete package install with new wiring and controls

Bringing your current setup to original spec vs refitting the power package to a new(ish) mercruiser 3.0L alpha setup is imo six of one, half a dozen of the other financially

So, aside from the engines they came with in the '70s, is there no new(ish) engine compatible with the Stringer 400? Does a new engine necessarily mean a new sterndrive?

 

[M0bi0us0ne]

The only sterndrive setup compatible with your current transom is an omc sterndrive colloquially known as a stringer drive

If you choose a mercruiser package you'll definitely need to rebuild the boat transom prior to install along with cutting, fitting, complete package install with new wiring and controls

Bringing your current setup to original spec vs refitting the power package to a new(ish) mercruiser 3.0L alpha setup is imo six of one, half a dozen of the other financially

What do you mean by "bringing my set up to the original spec"? having the engine completely rebuilt?

 

[matt167]

You can fit up to a 1990 Mercruiser, OMC or Volvo 3.0L wit the correct exhaust manifold.. stringer was never used behind a one peice rear main so 1991 and after one piece engines are out… the engine itself is just a fork lift engine

To convert to mercruiser, is a whole can of beans

 

[dubs283]

Thanks, Matt

Got a bit ahead of my brain with typing. A two piece rms GM 3.0L will bolt up to the intermediate housing included in your current setup

The drive, separate of the intermediate housing will not be compatible with any mercruiser package (transom assy)

Side note (and unrelated to omc) : if anyone reading this knows about the now antiquated mercruiser tr/trs engine and drive package I saw a 1984 24' sea ray cuddy fs on clist locally. Took a minute to recognize the drive in the pics and my first thought was, "I wonder what engine is in front of that?" Pics were lacking interior views. Only reason I have for mentioning this is the tr/trs package is the closest mercury ever came to resembling a stringer package

 

[M0bi0us0ne]

ok, so the quicksilver is out of the question; what about this?

GM 3.0L & 3.0LX new Base Engine, marineparts.eu

marineparts.eu

www.marineparts.eu

 

[matt167]

ok, so the quicksilver is out of the question; what about this?

GM 3.0L & 3.0LX new Base Engine, marineparts.eu

marineparts.eu

www.marineparts.eu

If you make sure the one they ship you is a 2 piece rear main then yes it’ll work

 

[M0bi0us0ne]

If you make sure the one they ship you is a 2 piece rear main then yes it’ll work

Excuse my ignorance, but what does 2-piece rear main mean?

 

[matt167]

The rear main seal. The crankshafts have a different bolt pattern, and your old OMC can only bolt up to the old stuff

 

[Scott Danforth]

Excuse my ignorance, but what does 2-piece rear main mean?

1990 or older motors used a 2-piece rear main seal.

In 1990 the 3.0 was redesigned to use the same rod and piston in the 5.7 (for parts commonality) and the crank seal was redesigned to a 1-piece.

 

[Scott Danforth]

The best think you can do is redo your transom and stringers to use either a late model Mercruiser motor and drive, or a late model Volvo Penta motor and drive.

This will require replacing the transom

 

[M0bi0us0ne]

ok got it! thanks everyone