What do I have OMC 400-800?

[OMC73]

Been doing a lot of research for my 73 omc and I have some questions on terminology. On my out drive it says it's a 140 hp but my motor is a 120 hp. I've seen the term "Stringer", "Sterndrive", and "400-800 series" on my internet searches and YouTube videos. From what I can tell they are similar to what I have.

I basically know that I have a low profile, electric shift, and that it is a 140 hp model. Could somebody clarify if what I have falls into the category of 400-800 series or if it's a stringer or both? Basically any information or history that pertains to my out drive would be great.

Thanks!

 

[southkogs]

On a '73 it's just an electric shift. Post '77, the hydro-mechanical and mechanical shift Stringers were designated 400 for 4 cylinder engines and 800 for 6 and 8 cylinder engines.

In 1973 a 120 HP OMC was a 153 CID Chevy II engine (inline 4) and would carry an OMC model number of 990206 or 990206 (F or S depending on if you have select trim). You should be able to find the model number on a tag at the back of the engine, typically on the starboard side near or on the motor mount.

The outdrive was an electric shift. Hopefully, you've got the exhaust housing or the top cap from a 140 (which is where they displayed their HP) and the rest of the drive is a 120 drive. Physically they are pretty much the same, but the ratio is a little different between a 140 and a 120.

The system is called a Stringer because unlike the Mercruiser drives, the OMC Stringer mounted to the stringers of the boat. Volvo and Mercruiser mount to the transom ... or better stated, the Merc and Volvo drive exert more force and transfer of energy via the transom. The OMC doesn't even touch the transom ... it passes through and exerts all of it's force on the stringers of the boat.

 

[OMC73]

Thank you for the great information. To clarify I have a couple questions. Should my out drive also be a 120 to match up with the motor? How can I tell if I have a 120 out drive with a 140 exhaust cover?

 

[Redrig]

on electric shifts ALL of the lower units are the same . The changing in gearing between 4 bangers and v8s is done in the upper case.

you should have a tag on the upper that will give you a number , or if you ever have it apart you can count the gears in the upper.

if you didn't have a upper made for that small engine , you would know .... it would be an absolute dog.

 

[southkogs]

^^^^ Yup

Have you had it running out on the water yet?

 

[OMC73]

^^^^ Yup

Have you had it running out on the water yet?

I have not had it on the water yet. I'm close though, I got the engine running the other weekend (finally!!) and it shifts into gear good. I could take it to the lake for a test run but my free time is at a premium lately. I'm pondering a water pump job in the out drive since I have no idea when that was done last. I rebuilt the carburetor so that needs some fine tuning (but it runs so that's a good sign) and I need to build an engine cover and replace some gauges. I think doing the water pump and tuning the carb are the only things that have to be done before I take it for a test run.

There is a tag on the upper with the numbers on it. I will check it out when I get home today and see what it turns up. I'm sure it all matches up... I hope lol

 

[southkogs]

Change the impeller for sure. It's really an every two or three year service item.

Also: change your stern drive lubes if you haven't already: The intermediate and the upper can use typical SAE90 stuff you can find anywhere, but your lower needs Type C for your electric shift. There are several greasing points that you should probably grease up - and don't miss the zerk behind the red cover on the front of the stern drive: that greases your swivel bearing and can help keep exhaust gasses out of the cooling system.

After that, if the hull is seaworthy - plop it in and try it out.

The ratio of the 120HP upper is 16.20, and the ratio on the 140HP upper is 19.20. Overall ratio is 1.92 on the 120 vs 1.61 on the 140. (knew I had 'em somewhere)

 

[OMC73]

Just want to verify this is the correct kit that I will need? see below

 

[OMC73]

[No message]

 

[southkogs]

That's it: But call iBoats:

http://www.iboats.com/Sierra-18-338...6033754--session_id.965170864--view_id.187584

Check on your forum discount and the price match guarantee.

 

[OMC73]

That's it: But call iBoats:

http://www.iboats.com/Sierra-18-338...6033754--**********.965170864--view_id.187584

Check on your forum discount and the price match guarantee.

Will do thanks!