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TOPIC: Short Shaft 650 questions

Short Shaft 650 questions 8 years 7 months ago #1717

  • classicfins
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Ok, I'll help get this forum started. I have a long shaft 650 Merc, probably a early to mid 70's unit. I picked up a early to mid 70's short shaft mid section last week that I found laying in an abandoned bass boat. I am attaching pics of what I have, along witha pic of the serial number.

Now, supposing the years on the motor and this mid section are compatable, could I (eventually after collecting the rest of the parts) convert the long shaft 650 to short? Is this even feasible? I know nothing about these things in this aspect, but would like to see what the merc gurus have to say. I know at the very least I would need either a short shaft lower unit or short driveshaft, etc.

I also have a couple of 80/85 horse Mercs that would be about the same year model as my 650 and I might even want to use one of those if possible.

So, can someone school me on this conversion? Explain the process, provide a parts list, tell me I'm dreaming, anything. lol. If it's do-able and I have a list of what is needed I can start gathering parts and pieces. Thanks guys!
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Re:Short Shaft 650 questions 8 years 7 months ago #1743

  • g3jim
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you need to be sure the exhaust adapters at the bottom of the block with it meets the intermediate housing match. I can help with any short shaft conversion. I have lower units, NOS shafts etc....
You should be OK to put the 650, 800 or 850 as long as the ports will match up to the exhaust adapter. If that is good simply transfer the top end of your motor to the short shaft intermediate housing. When you grabbed the short mid did it have the upper shift shaft water tube with it?

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Re:Short Shaft 650 questions 8 years 7 months ago #1750

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This is all I got. The boat is still there so may be some parts inside the boat that I didn't see. I didn't take too much time because it was pouring down rain. I will be back over that way next weeka nd will see what else I can find, if anything. Thanks Jim,
Doug

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Re:Short Shaft 650 questions 8 years 7 months ago #1753

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my pleasure! Pouring here too. Windy as all get out

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Re:Short Shaft 650 questions 8 years 7 months ago #1780

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Doug;From what I see in the pictures you have a 650 3cyl mid. The 800 & 850 parts are not compatable. Pre 1970 650 4cyl & the 800 & 850 & all 6 cyl legs are compatible but vary with years. Let me elaborate. 1961 thru 64 650 & all 6cyl will interchange. The legs are all alike. 65 thru 71 650 800 4cyl & the 6cyls all use the same leg except the 650 3cyl. 72 thru 88 all 4 cyl & inline 6 motors use the same leg. The 650 3 cyl uses the same leg as a 500 402 400 or 350 .
Tim

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Re:Short Shaft 650 questions 8 years 7 months ago #1800

Master Tim is correct.
You need to find a short mid that has (2)studs side-by-side where the pictured mid only has one centered stud.
Then,...Like Master Tim stated,...There are (2) varieties of the shorty mid you seek.
One that will work under your 650ss 4 cyl and a few 800 & maybe 850 4 cyls with the correct exhaust extension plate,...And the other mid and related exhaust extension plate required under '72 and later Inline-6s and some 800 and 850 4 cyls. (I say 'some' when I reference the 800 & 850 4 cyls because I have not researched the specific serial groups and related year models of these 4 cyl models that became 'dual square-port' exhaust configuration rather than the 'oval' required for your 650ss 4 cyl.
(more like the shape of Texas that 'oval' & very similar to the exhaust tuner shape you picked up off a 650-3, but a bit larger and will not have the control cable retainers cast onto the exhaust extension plate like the one you have)
Thom

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Re:Short Shaft 650 questions 8 years 7 months ago #1805

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I didn't even notice the pattern for the studs in the mid. I guess I looked too quickly. Sorry if I have misinformed you.

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Re:Short Shaft 650 questions 8 years 7 months ago #1877

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Thanks guys!

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Some people are like slinkies... Not much good for anything, but they sure are fun to push down the stairs.
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