1964 merc 850 6cyl lower unit compatibility

[Chinpoker]

Hi wondering if anyone can tell me what years and HP lower units will bolt on to my motor S/N 1664924

 

[Chinpoker]

Re: 1964 merc 850 6cyl lower unit compatibility

Would lower or higher HP units be OK from what years also so to broaden my available searches online hard to find my exact motor for parts in Ontario, Canada lots a lower HP and higher or not even from 1964 please really need your expert opinions!!

Thanks
Dave

 

[Chinpoker]

Re: 1964 merc 850 6cyl lower unit compatibility

Would a 1966 950 Lu work direct swap with no modifications

 

[Chinpoker]

Re: 1964 merc 850 6cyl lower unit compatibility

Or a 67' 650

 

[emckelvy]

Re: 1964 merc 850 6cyl lower unit compatibility

Those L/U's will fit, but not without modifications.

You'd cut the shift shaft of the later-style L/U to the same length as the '64 L/U. Measure from the mounting flanges of the old L/U for correct length. Chamfer the end of the cut shift shaft and deburr the splines, and it should slide right into the shift coupler.

Next step is to cut a chunk out of the plastic reverse lock spoolpiece, and modify the brass shift cams so the reverse lockout hook works correctly (i.e. locks down in both Neutral and Reverse).

As I recall, I flipped the cams upside-down, such that the upper cam with the 2 "tangs" went into the shift-shaft cavity in the lower unit, and the lower, round shift cam went down onto the shift shaft to mesh-up with the other cam.

Had to grind the upper cam to fit in the shift cavity.

It's been almost 30 years since I did that mod, though! You'd have to carefully fit the pieces and make your measurements so the lockout hook latches down like it's supposed to, as I can't recall the exact measurements, etc.

Lastly, the 850 has no exhaust tube. So, when using a later-style lower unit you'd need to cover the little side-vents with a plate (or other material such as epoxy to plug 'em up). Otherwise the exhaust noise thru the vents will be quite loud.

Any '64 or earlier FGS (Full Gear Shift) Inline Six L/U will fit without mods. Also from a 650-4 of same vintage.

Otherwise you'll have to source a later-style L/U and do the alterations.

HTH.............ed

 

[Chinpoker]

Re: 1964 merc 850 6cyl lower unit compatibility

Hey emckelvy thank you for your help pretty hard to locate parts locally up here had some maybes but fell thru closest I've found is Rochester,NY if only my motor was still working I'd just take a Cruz across the lake lol :facepalm::doh::doh:

 

[Chinpoker]

Re: 1964 merc 850 6cyl lower unit compatibility

Those L/U's will fit, but not without modifications.

You'd cut the shift shaft of the later-style L/U to the same length as the '64 L/U. Measure from the mounting flanges of the old L/U for correct length. Chamfer the end of the cut shift shaft and deburr the splines, and it should slide right into the shift coupler.

Next step is to cut a chunk out of the plastic reverse lock spoolpiece, and modify the brass shift cams so the reverse lockout hook works correctly (i.e. locks down in both Neutral and Reverse).

As I recall, I flipped the cams upside-down, such that the upper cam with the 2 "tangs" went into the shift-shaft cavity in the lower unit, and the lower, round shift cam went down onto the shift shaft to mesh-up with the other cam.

Had to grind the upper cam to fit in the shift cavity.

It's been almost 30 years since I did that mod, though! You'd have to carefully fit the pieces and make your measurements so the lockout hook latches down like it's supposed to, as I can't recall the exact measurements, etc.

Lastly, the 850 has no exhaust tube. So, when using a later-style lower unit you'd need to cover the little side-vents with a plate (or other material such as epoxy to plug 'em up). Otherwise the exhaust noise thru the vents will be quite loud.

Any '64 or earlier FGS (Full Gear Shift) Inline Six L/U will fit without mods. Also from a 650-4 of same vintage.

Otherwise you'll have to source a later-style L/U and do the alterations.

HTH.............ed

How about a 1970ish 80hp just got a reply from a shop?

 

[emckelvy]

Re: 1964 merc 850 6cyl lower unit compatibility

It'll bolt up too, with the same mods. If it doesn't have an O-ring groove on the driveshaft to seal the crankshaft area, you'd have a few options:

1) Pull the 850-6 powerhead & install the later-style stainless O-ring carrier & O-ring at the end of the crankshaft. The carrier just taps in the end of the crank (Note: P/N & description: "54196A 6 - CARRIER ASSEMBLY", list price: $14.11)

2) Grind an O-ring on the donor L/U's driveshaft in the same location as the old L/U's. I've ground 'em by hand in the past, but the shaft could be easily chucked into a lathe and machined proper;

3) Don't do either but make sure the driveshaft splines are greased really well and pull the L/U down more frequently for regreasing.

I'd only recommend #3 if you were running in fresh water. Salt water will rapidly corrode & rust out the crank splines if there's no O-ring to seal the grease in.

BTW, your 850 will really like the 2.3:1 gear ratio that the 66-C.I. 80hp carries; I had a similar L/U on my old '64 850-6 and it ran very well. Also bolted a set of 100hp carbs which was a big improvement in performance! A true "1000" 100hp also has larger reed valve stops than an 850-6, but even so the larger carbs did great.

That ol' motor with a beat-up 2-bladed "speed" prop on a 14' Fiberform V-hull runabout did 50 mph on a glassy-calm lake one beautiful September day back in the 80's; with a ski prop she'd do a solid 44-45 and pull like the Dickens!

HTH & G'luck with the L/U search.........ed

 

[Chinpoker]

Re: 1964 merc 850 6cyl lower unit compatibility

It'll bolt up too, with the same mods. If it doesn't have an O-ring groove on the driveshaft to seal the crankshaft area, you'd have a few options:

1) Pull the 850-6 powerhead & install the later-style stainless O-ring carrier & O-ring at the end of the crankshaft. The carrier just taps in the end of the crank (Note: P/N & description: "54196A 6 - CARRIER ASSEMBLY", list price: $14.11)

2) Grind an O-ring on the donor L/U's driveshaft in the same location as the old L/U's. I've ground 'em by hand in the past, but the shaft could be easily chucked into a lathe and machined proper;

3) Don't do either but make sure the driveshaft splines are greased really well and pull the L/U down more frequently for regreasing.

I'd only recommend #3 if you were running in fresh water. Salt water will rapidly corrode & rust out the crank splines if there's no O-ring to seal the grease in.

BTW, your 850 will really like the 2.3:1 gear ratio that the 66-C.I. 80hp carries; I had a similar L/U on my old '64 850-6 and it ran very well. Also bolted a set of 100hp carbs which was a big improvement in performance! A true "1000" 100hp also has larger reed valve stops than an 850-6, but even so the larger carbs did great.

That ol' motor with a beat-up 2-bladed "speed" prop on a 14' Fiberform V-hull runabout did 50 mph on a glassy-calm lake one beautiful September day back in the 80's; with a ski prop she'd do a solid 44-45 and pull like the Dickens!

HTH & G'luck with the L/U search.........ed

Last but not least 64' 1000 LU should bolt right up right no mods
Thanks again for any advice
Chin