ID odd length Lower unit 9.9/15hp series

retroroy

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A local junk guy who prowls the streets here on trash night brought me five OMC '74-92 style 9.9/15hp lower units. He was asking $5 each and they look new. They shift and feel fine, but two are painted a bright green, the green like Johnson used in the mid 1950's but these are 70's or 80's style lowers. Its not the typical gold/green they used on various models in the 70's, its a

At a glance I had figured they were at least long shaft lowers, but that's changeable but when I sat one next to a 20" shaft lower unit I had off at the time the driveshaft on these five dwarfed the 20" model by 12" of driveshaft length?

I grabbed one for a Sailmaster, and this is 7" longer.
I see only three shafts listed for the 9.9/15hp motors, a 15", a 20", and a 25". This driveshaft is 7" longer.
Did they make a super long shaft? Maybe a Pontoon model or something?
Ever see a bright green 9.9hp in this series?


The guy said he pulled them from a dumpster somewhere. They were full of oil, hold pressure and look to be never used. Oddly the shifter rod is the same as a 20" motor.
Other than the driveshaft length they appear to be the same as any other gear box from this era besides the color. Those that are painted green appear factory painted, no paint on any hardware, no runs and the finish seems really hard. If someone painted them this color it was likely apart when it was painted. Those with no paint are smooth unsanded aluminum.
 

rolmops

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Is it just the driveshaft that is longer or is it the lower unit housing as well?
I have heard something about house boats that used 2 or 3 of the 5 inch extension pieces to make the engine more accessible for service, but that was a long time ago.
Another thing I have heard about is using the 9.9 in sewer ponds on dairy farms to oxygenate the water and clean the water a bit before it going into the run off
 

retroroy

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Only the driveshaft is longer, the shifter rod is the same as a 20" motor and the gear case housing is normal. I have a few Sail master and Yachtwin motors here an they have a long spacer but they're not nearly as long as these things.
I've been all through the 74-92 parts listings and can't find anything but 15, 20, and 25" driveshaft option?

I do have a pair of mid 70's Chrysler 12.9hp "Sail" motors that have a 32" shaft length and a big foot style lower so I know someone was making longer motors then, but can't find any listings on them. These would likely be even longer than those two Chrysler motors. (The Chrysler 12.9 power head is in the same family as their 9.9hp).
 

rolmops

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When you look at the actual shaft, does it look like it could be cut in 2 and fit 2 short shaft outboards? Maybe somebody just machined a double length short shaft , but never got around to cutting it in two and finishing the job.
 

racerone

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Maybe they just stuck a shaft in there to close the hole .----Keep oil in and dirt out.---Pictures will help.
 

retroroy

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I pulled the drive shaft out of the one.
It measures 42 5/8" overall

The oil in the lower units is brigt blue and super thick. I thought it was grease at first but its the consistency of thick glue. Its spot clean though.
The lower housing is completely normal other than the shaft. The shift rod is identical to the one out of my 20" shaft 15hp.

IMGP0089.JPG
 

retroroy

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Could these shafts be out of a different model?
The longest shaft I see listed is 32 3/8" for a 25" motor.
The shift rod is the same as a 20" (I do have a bag of short shift rods so that part is covered.)
I don't have enough short drive shafts.
Has anyone cut and made a longer shaft shorter?
I can cut a bit out of the middle to make these the needed 22 3/8" long and weld and machine them so they remain smooth so the impeller will pass down over the shaft.
I'd weld, and stress relieve it with some heat before machining and polishing. I'm thinking a diagonal cut would be stronger than a butt joint.
Or maybe a keyed type joint then weld?
I don't suppose these make enough power to be all that much of a concern either.
Any ideas on cutting the shafts to fit?
 

retroroy

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Not sure why the lower itself didn't show up, but heres one of the green one's again. There are two like this and three in bare aluminum.

IMGP0101.JPG
 
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