Omc Compatability

[Sugo]

Will a 3.8L Omc motor be a suitable replacement for a 3.0L OMC (Is it the same block ?)
Thanks for any info.

 

[RotaryRacer]

Re: Omc Compatability

NO. The 3.8L must be from an old stringer drive....it is a Buick V6. The 3.0L is inline 4 cylinder based on a GM block...the same one that Mercruiser and Volvo Penta are still using.

They are very different motors.

 

[Sugo]

Re: Omc Compatability

Thanks for your time

 

[cr2k]

Re: Omc Compatability

That's not entirely true. The 3.8 is also a Chevy V-6 which I have in my stringer drive.

Is your outdrive a stringer mount?

There will be a difference in the gear ratios however, the 3.0 having a lower ratio than the 3.8.

What year is your drive/boat?

 

[Sugo]

Re: Omc Compatability

The boat I am working on is an 88 Bayliner Capri. It has a omc cobra leg. The OMC 3.0 that is in the boat now suffered a cracked block and head due to the cold snap last week in B.C. I purchased the boat without confirming the water had been drained. I am looking for the most economical way to close this chapter. I am committed to finishing this project as I have already replaced the floor, new carpet and re-upholstered the entire interior. It is my first and last in-board project. I think I will stick to what I know next time. My personal boat is a 18.5ft Double Eagle with a 90 Mairner outboard, (Much better for my other hobby, fishing) I don't know what a stringer drive is, Sorry, I am getting the crash course in inboard motors and drives.

 

[HT32BSX115]

Re: Omc Compatability

Your other choice could be a complete swap.

http://vancouver.en.craigslist.ca/bnc/boa/1492681610.html

I think the guy above is in lala land with his price ......I paid a little less ($5k USD) for my complete 454/Bravo setup a few years ago....

But there's a lot of deals like this on craigslist from time to time and there's a LOT of parts on ebay....


Cheers,


Rick

 

[RotaryRacer]

Re: Omc Compatability

That's not entirely true. The 3.8 is also a Chevy V-6 which I have in my stringer drive.

The V6 that the 3.8 OMC was derived from is what GM called the Buick V6. Since it is under the coporate umbrella of GM it was used in seveal of the GM brands...Buick, Chevy, Pontiac, Etc.

http://en.wikipedia.org/wiki/Buick_V6_engine

 

[RotaryRacer]

Re: Omc Compatability

Also, to answer a few other questions.

OMC Stringer = this is the drive system that OMC came up with to compete with Mercruiser and got around the patents the Mercruiser had in place on their outdrive. The simple distinguising difference between them and the later OMC Cobra is the way the trim is adjusted. For the stringer driver there is a mechanism that tilts the entire engine and drive unit together. On the Cobra drives there are two hydraulic cylinders that move the outdrive up and down on the outside of the boat...similar to Mercruiser. The basic OMC stringer drive design was in production from 1962 through 1985. The Cobra replaced it in 1986.

http://www.glmmarine.com/30yearsomc.html



Oh, and the 3.0 liter that is attached the 1988 OMC Cobra is actually derived from the Chevy inline 6 that is in my Four Winns. GM made a 4 cylinder version and used it for a few things and now they are still produce the blocks at 181 CI (3.0L) for marine use.

http://en.wikipedia.org/wiki/Chevrolet_Straight-6_engine#153

 

[RotaryRacer]

Re: Omc Compatability

The V6 that the 3.8 OMC was derived from is what GM called the Buick V6. Since it is under the coporate umbrella of GM it was used in seveal of the GM brands...Buick, Chevy, Pontiac, Etc.

http://en.wikipedia.org/wiki/Buick_V6_engine

Ok, I think I'm wrong. I have done a little more research.

In 1980 Chevrolet introduced a 90degree V-6 and it was offered at 3.8L (229 CI) displacement.

I thought that I had recalled seeing OMC sterndrive applications well before 1980 that were listed at 3.8L. Now that I have looked into it a little more it would appear that the first year OMC offered the 3.8L V6 was 1981.

Also, even though the Buick V6 was 90degree it was setup to use the bellhousings from the smaller 60degree V6s. This would make it harder to adapt to a marine application.

The Chevy V6 would accept the same bellhousing as the small block V8 that OMC also offered at the time.

And if that wasn't enough to prove myself wrong this little tidbit from the official Evinrude/OMC parts website helps: "CRANKCASE ASSY. PARTS AVAILABLE FROM LOCAL CHEVROLET DEALERS".

Oh, and then there is this, the adapter housing assembly is p/n 0981552 for the 3.8L and the 230HP V8. The only was that is possible is if the blocks have the same bolt pattern and essentially the same design.

So, consider youself proven 100% wrong on the assertation that the OMC 3.8L was a Buick derived motor RotaryRacer. Geesh, what an idiot.

http://en.wikipedia.org/wiki/Chevrolet_90-Degree_V6_engine#3.8L_.28229_CID.29

 

[Lou C]

Re: Omc Compatability

One way to tell for sure is that the Buick based 3.8 (225 cu in) was based on a Buick V-8 and these had the distrubutor in the FRONT...the Chevy based V-6s (some were 90 degree V-6s derived from the small block 350 V-8 such as the well known 4.3...some were designed as V-6s and had a 60 degree angle between the cylinders such as the 2.8 and its variants) had their distrubutor in the REAR...
the simplest way to solve this problem and get this boat running is to just get another 3.0 4 cylinder...any swap to a V-6 is going to be a LOT more epensive because you will have to change the engine mounts...ALL of the exhaust system all the way to the Y pipe and the ratio in the drive uint will be wrong for a V-6....it would only make sense if you had a donor boat and could swap out the whole driveline to a Merc set up and also could do the 'glass work for the engine mounts....

 

[cr2k]

Re: Omc Compatability

The SIMPLE distinguishing diff for a stringer mount is the big rubber transom boot around the drive.

 

[getemkustom]

Re: Omc Compatability

Here is a picture of a Buick V6 I have in mine with a OMC out drive

 

[RotaryRacer]

Re: Omc Compatability

Here is a picture of a Buick V6 I have in mine with a OMC out drive

Ok. So I was sorta right. I thought I had seen a Buick V6 attached to an OMC that was built well before 1981.

getemkustom,

What year is that? I assume that is the original motor to the drive and boat, correct? I would guess it is early-mid 70s?

 

[RotaryRacer]

Re: Omc Compatability

Ok.

This makes more sense now.

GM sold the Buick V6 engine design and tooling to Kaiser-Jeep in 1967. At that time it was a 225 CID block.

OMC first entered the outdrive market in 1968. They offered a 155 HP v6 based on the Kaiser-Jeep supplied blocks.

Kaiser-Jeep was purchased by American Motors in 1970 and they transitioned to the AMC straight 6. 1971 was the last year they used the "Buick" V6.

OMC dropped the 155HP v6 after 1972. I assume that it could have something to do with AMC dropping the engine from regular production.

GM bought the design and tooling back from AMC in 1974 and the rest is history.

OMC didn't offer another V6 until 1981 as discussed earlier this was a Chevy based motor.

So, the boat in the pictures posted by getemkustom must have been built between 1968 and 1972.

So, the lesson here:

OMC V6 from 1968-1972 = "Buick" V6 at 225 CID (3.68L) model 155HP, distributor in front

OMC V6 from 1981-1985 = Chevy V6 at 229 CID (3.75L) modle 3.8L, distributor in rear

 

[getemkustom]

Re: Omc Compatability

Ok. So I was sorta right. I thought I had seen a Buick V6 attached to an OMC that was built well before 1981.

getemkustom,

What year is that? I assume that is the original motor to the drive and boat, correct? I would guess it is early-mid 70s?

1969 Johnson Tri Hull - all original

 

[RotaryRacer]

Re: Omc Compatability

Nice!!