Mercruiser III

[smokeonthewater]

Hey anyone know anything about a merc III..... A buddy of mine is picking up a rotten 23' sea ray with a HUGE black outdrive.... We are gonna strip it for parts and we have considered using the drive but it looks like it would require a bigger cutout in the transom than the r/mr/alpha..... if this thing fails and is not reasonably repairable it pretty much would be the death of the hull since it wouldn't be worth rebuilding the transom to us...

Best I have found so far is this thing was 68-71 ish in production... I found an old add stating that it was a hydraulic trannsmission and that it shifted VERY smoothly..... This thing swings a 20" wheel so if it were to prove to be a reliable unit it would likely be a good match to the 6000 lb single engine cruiser we were thinking of putting it in..... In the add they were running two of them and getting 32 mph out of a big houseboat with twin 250 hp v8's in 1968

I have seen it spec'd with big blocks so it seems that it is a pretty robust design....

At the very least we'll use the exhaust manifolds and if it works the coupler and bellhousing with an r/mr setup

Obviously this is po boy backyard wrenching and not a "correct" restoration

Biggest concern is lack of (used) parts availability


did I mention it was BIG

 

[Don S]

Re: Mercruiser III

If you go up to the Adults Only sticky, you can download service manual #1, it covers both the sterndrive and the transmission. There is no shifting in the drive at all, if the input shaft turns, the prop shaft turns.
The 250 engine was a 327 chevy, the III drive was used on some big blocks, the 427 and the 482.
Some parts, like the gears are NLA, gaskets, seals, bellows, and stuff like that is still available. But gears, and special parts like the input shaft yokes are NLA from Merc, and the chance of finding them used will be slim to none.

 

[smokeonthewater]

Re: Mercruiser III

well that makes sense as the billed it as "inboard shifting with an i/o drive"

any experience with the reliabilaty of these 40 year old drives? Also what prop does this thing use? It is a 20" vented hub.... same as bravo?

 

[smokeonthewater]

Re: Mercruiser III

anyone else? I thought for sure Bondo would chime in on this

 

[HT32BSX115]

Re: Mercruiser III

Ok,

I'll always bite ......

I know what a Mercruiser II drive is.........What's a III?


Regards,


Rick

 

[Bt Doctur]

Re: Mercruiser III

1968-1972 scroll down to the bottom part , look for "III"
http://www.marinepartsexpress.com/merc_sch_fs.html

 

[Don S]

Re: Mercruiser III

I know what a Mercruiser II drive is.........What's a III?

Read the previous replies Rick, all kinds of info on a III in the OEM service manual, it's basically a pre TR drive.

 

[HT32BSX115]

Re: Mercruiser III

Got it, thanks!


I guess every time I saw a reference to a III, without looking any further, I just assumed that someone hit the "I" one too many times!

 

[haulnazz15]

Re: Mercruiser III

Or that they forgot to put the word "Bravo" in front of it.

 

[smokeonthewater]

Re: Mercruiser III

okay.... I guess I don't ask questions very well soooooo


1: Should we consider using this drive?

2: Are they considered fairly reliable?

3: Does this thing have any value other than scrap metal?

4: Are there any problems specific to this drive to look for?

 

[Don S]

Re: Mercruiser III

1: Should we consider using this drive?

Not unless you are into restoring antiques, and can deal with the prices of parts for it. The ujoint assembly was over $2,000 before it went extint

2: Are they considered fairly reliable?

Way too old and unknown for that.

3: Does this thing have any value other than scrap metal?

Only if someone is looking for III drive parts.

4: Are there any problems specific to this drive to look for?

They don't exist any more, and haven't since 1972. They are old, and they weren't that popular. Mostly because they were only on the bigger boats with higher HP engines.

 

[smokeonthewater]

Re: Mercruiser III

Does this thing have a bigger cutout in the transom than the alpha?

 

[Don S]

Re: Mercruiser III

I have no idea, never seen a cutout for one.

 

[smokeonthewater]

Re: Mercruiser III

ok thanks...... I just thought to look though the special tools section of my merc manuals.... Maybe I can see which cutout tool works for these....

 

[smokeonthewater]

Re: Mercruiser III

Well it calls for the C-91-48703A2 transom cutout and drilling fixture but it doesn't look like any other drive shares it.... still looking but we may just have to wait till we get it apart.... we may still try it out if it doesn't require a bigger cutout than an alpha can cover but otherwise it will go in the pile.... I had figured it for a dinosaur but thought there was a slight chance for a "those things were bombproof" conclusion.....