Sterndrive Model?

Jamepc · Apr 29, 2005

What model sterndrive am I most likly to have coupled to my '85 Mercruiser 120? R, MR, Alpha, Alpha Gen II....? I have the lower unit listed on Ebay and want to put the correct model number in the description. Thank you.

achris · Apr 29, 2005

Re: Sterndrive Model?

1983 is the 'R'. You should also list the ratio, which for the 120 is 1.98:1 It will fit on any V8 engine up to 1990, or in-line from 1983 to 1990. Chris...... Before the 'editors' jump all over me, yes I know that the V8 chevs use 1.5:1 ratios. You can still use the 1.98:1 if you change the prop.

Bondo · Apr 30, 2005

Re: Sterndrive Model?

And I Thought the 83/93 was the MR/Alpha 1........ 1985 I Know is an Alpha 1....... And,.... The Alpha 1s,+ the Pre-Alpha R drives,.. All have a 1.65/1 ratio in the Lowerunit.... Final Drive Ratio is determined by the Upperunit Ratio......... Chris,..... You otta Go Fishing...... Or to Kamchatka.........

achris · Apr 30, 2005

Re: Sterndrive Model?

Originally posted by Bondo: Chris,..... You otta Go Fishing...... Or to Kamchatka.........

I know, I know!!! Talked to the boss yesterday and he's got me on a job in the Phillipines, starting in about a week. That should keep me off the streets

In the meantime, have a look at this chart, taken from the Mercruiser Service Training notebook. It lists the years and models of engine and drive units. Interesting that the MR was only used for one year, 1985. There's another page (not scanned) that shows the Gen II first started in 1992. Chris..........

Bondo · Apr 30, 2005

Re: Sterndrive Model?

OK,...... So,... The Lower unit in Question is an "MR",...... Which is the Transistion unit from the "1-R" to the Alpha...... I Believe the "MR" is More of an Alpha,.. Than it is an "R"....I know the "MR" Looks like an Alpha..... Atleast as far as Interchangeability....... I guess that My timeline would be More accurate if I said the "R"s were used To 84,+ the Alphas were used up To 93,+ the "GenIIs" there after.......

achris · Apr 30, 2005

Re: Sterndrive Model?

Originally posted by Bondo: OK,...... So,... The Lower unit in Question is an "MR",......

Yeah, howd I miss that? Sorry James. Original post said '85 and I go giving the data for '83. Time for a holiday! If you need me, I'll be packing my bags (for Petropavlovsk

) Chris.........

Jamepc · Apr 30, 2005

Re: Sterndrive Model?

So would the '85 be a Pre Alpha or Alpha Gen I or more of a mixed breed unit? Thanks for the replies! James

achris · Apr 30, 2005

Re: Sterndrive Model?

James, Look at the chart. 1985 is MR, that's before the Alpha. "Pre-Alpha" covers everything before 1986; MR, R and MC-1. Chris.........

Jamepc · Apr 30, 2005

Re: Sterndrive Model?

Chris, I did look at the chart, thanks it was very helpful. But like Bondo stated, it's more like an Alpha unit then a pre Alpha. How about the lower unit itself. Is that pre Alpha or Alpha (not in name but characteristics). Should it work with all Alpha Gen I upper units? Thanks again for the clarification. James

Bondo · Apr 30, 2005

Re: Sterndrive Model?

For Lower Unit Interchangeability,........ Look for the "Pre-Load Pin" in the Input Shaft........ Those With the pin are for Pre-Alpha, Rs, Mod.1s, etc...... Those WithOut the pin are a Swap for the Alpha 1s,.... Up To(but Not including) the GenII in 93........

Should it work with all Alpha Gen I upper units?

Ayuh,........... So long as there's NO "Pre-load Pin".................

achris · Apr 30, 2005

Re: Sterndrive Model?

Personally I don't like the term "Pre-Alpha", that covers too many units. I prefer to call an R unit an R. No confusion then. Many of the parts in the MC-1, R, MR and Alpha Ones are the same, or the earlier ones supercede t the later ones. Most of the parts in the upper unit are the same. The lower unit is a bit different because they changed the direction of load on the drive shaft bearing. The earlier ones had a pre-load pin in the top of the shaft, thus the bearing (under the water pump) was installed to take the load in that direction. The later ones (MR and Alphas I think) have no pin and only when there is load on the shaft does it rise up and the bearing takes the load. As for your unit, the top and bottom housings are completely interchangable with the other various units. You can use an MC-1 top with an A1 lower, or an A1 upper with an MR lower, whatever you like.

Should it work with all Alpha Gen I upper units?

Short answer? Yes. Sorry about the confusion. Chris.

Bondo · Apr 30, 2005

Re: Sterndrive Model?

Personally I don't like the term "Pre-Alpha", that covers too many units. I prefer to call an R unit an R. No confusion then.

Agreed,........... But,... It Still gets Extremely Confusing....... 'Cause,.. Is that R-drive a 888,.. or a 898,..... or a 470,..... or a ??????????????????? Mercruiser Likes to give Hundreds of Names to essentually the Same Drives........

Jamepc · Apr 30, 2005

Re: Sterndrive Model?

I guess a pre load pin would be obvious, right? All I see at the top of the shaft is an o-ring.

Bondo · Apr 30, 2005

Re: Sterndrive Model?

I guess I Shoulda done this in the 1st place......... Look Here......................... Enjoy..........

Jamepc · May 6, 2005

Re: Sterndrive Model?

Bondo / achris, Thanks for the replies and links. You helped me answer many questions I received from people inquiring about my Ebay lower unit. Regards, James

Jamepc · May 9, 2005

Re: Sterndrive Model?

Bondo, Let me get a clarification here. The mercstuff.com site says the CASE is interchangeable. Does that mean a loaded (gears and all) Alpha lower will or will not fit a pre-Alpha? Or just the case fits? Thanks again! James

Bondo · May 9, 2005

Re: Sterndrive Model?

Does that mean a loaded (gears and all) Alpha lower will or will not fit a pre-Alpha? Or just the case fits?

I Haven't Tried it,....... But,.. I Understand that the Alpha Lowerunit Can be run on the Pre-Alpha Upperunit,........ But,.. Not the Other Way Around, Pre-Alpha Lowerunit on an Alpha Upperunit............ Hopefully Chris or Don or Rodbolt or Somebody will Clarify this...............

Sterndrive Model?

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