Help me figure out what studs I need

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OregonApe

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Joined
Jul 8, 2024
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LOCATION
Portland, Oregon
Ok, it's been a long, hot, bloody day, with little to show for it, but here we go.

Long story short, new to me boat came with a 2001 Mercury XR6 150 with a jet pump on it. It also came with what I believe is an unused factory prop lower. I want to switch to a prop. Motor is a long shaft, 20". Transom is a XL 25". After a lot of searching I found a used Bay Manufacturing 5" spacer kit to convert from 20" to 25". I thought it had the extended studs that I needed but now I'm not so sure.

As far as I can tell, all the studs are 7/16 14 TPI on the end that screws into the lower or the drive shaft housing and 7/16" 20 TPI for the nylon lock nut end. I looked up the front 3 studs on marineengine.com and added 5" for the spacer. Those first 3 are correct and screwed into the lower just fine.

However the next two..... I can't find them on any diagrams. Process of elimination though says that those must be the remaining 2 studs that came with the bay kit right? Well, I'm pretty sure one is bent from the marine salvage yard removing it from the motor they pulled the bay kit from, and the other I bent today. Who knows what damage I did to the threads of the drive shaft housing. The studs are the right length, but threads on the drive shaft housing are NOT 7/16 14 TPI or 7/16" 20FPI. They are also not 3/8" 16 TPI. I even tried cleaning them up with some stainless steel pipe brushes in a drill just in case some corrosion was holding things up. Nope, the one that I screwed halfway in and then fought for my life to get back out came out with also sorts of metal shavings. So I done messed up. The front three that went in were also really difficult, but not like this.

Also the rear bolt is shown as a 3/8"-16 x 1" on the diagrams but adding 5" for a total of 6" is WAAAAAAY too short. Also the hole in the lower is not threaded. So I need it to be longer. Somewhere between 8" and 9" I think.

Anyway, maybe I don't even need those middle two studs. The pump jet wasn't using them.

Sorry if I'm kind of ranting, it's just been a long day and I had basically no cell reception so I couldn't look stuff up. I spent hours trying to navigate a pdf of the service manual on my phone but every time I would change apps it would lose my spot in the PDF. Also, I'm really new to this and apparently I need to route the shift cable back into the motor and calibrate that up in the front control.

So can anyone tell me what is supposed to go in the highlighted spots so I can add 5" and try to find it? I can call bay again on Monday but their prices are offensive (it is honestly cheaper to buy the $800 kit than the accessory pieces).

https://www.marineengine.com/parts/mercury_marine_parts/sn/0T336461/1150454YD My motor if that helps. SN: 0T336461

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I only broke one 5/8" wrench getting this back out when I realized that it is not threaded 7/16-14.

20240803_140310.jpg
 
There are two studs listed in the exhaust/mid section housing diagram that appear to belong to those holes, part number for them is 16-56295. 7/16 diameter but no mention of thread pitch.

It looks like your long studs may be stainless, it's known to gall. I'd get a tap and try to chase the threads in both holes. If the threads on the studs are plugged with aluminum or corrosion you may want to run them through a die as well. Use a good lubricant when going together, grease is fine.

Absolute worst case, you can drill the holes out in the midsection and install a heli-coil or solid insert.
 
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