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Nissan NS8B removing lower unit problems

Demon76

New member
I have a 1993 Nissan NS8B which has never been serviced but ran fine this year after being idle for numerous years in a garage. I decided to replace the water pump impeller and got the kit. I removed the shift shaft pin and unscrewed three of the four lower unit bolts to drop the LU, but the 4th one broke off at the head. I can move the unit slightly back and forth but the unit wont drop. The bolts don't seem to engage any threads in the LU but only up into the housing above it, so it's logical to think it should slide out. I've used penetrating oil and banged on the unit with a mallet but it won't drop. Any thoughts?
 
Odds are the drive shaft is stuck in the crank shaft. Use wedges and patience. Lots of patience. Start with very narrow wedges, and as you gain a little gap, go to bigger wedges. Don't be surprised if it takes days. Also... If the prop struck an underwater obstruction, the shaft could also be twisted, but that is not too common.

Do not bang on the LU -- not even with a rubber mallet; if you get any result, it will probably be to break off part of the casting.

You may want to get a machine shop to extract the broken bolt.

After you finish servicing the water pump, be sure to grease the splines of the drive shaft before reassembling; don't get grease on the tip of the drive shaft, as that could prevent complete insertion.

If there is any water contamination of the LU lube, be sure to install a new LU seal kit as well.
 
Odds are the drive shaft is stuck in the crank shaft. Use wedges and patience. Lots of patience. Start with very narrow wedges, and as you gain a little gap, go to bigger wedges. Don't be surprised if it takes days. Also... If the prop struck an underwater obstruction, the shaft could also be twisted, but that is not too common.

Do not bang on the LU -- not even with a rubber mallet; if you get any result, it will probably be to break off part of the casting.

You may want to get a machine shop to extract the broken bolt.

After you finish servicing the water pump, be sure to grease the splines of the drive shaft before reassembling; don't get grease on the tip of the drive shaft, as that could prevent complete insertion.

If there is any water contamination of the LU lube, be sure to install a new LU seal kit as well.

Thanks for the quick reply.

The stuck drive shaft was my thought as well as I don't see the bolt with the broken head causing the LU to stay in place because the threads should not be engaging. I can get a paint scraper between the two units mostly on the non broken bolt side, but the other side doesn't seem to want to gap. What sort of wedges do you recommend? What about detaching the UU from the motor via the 6 bolts up there? Seems like a lot of work to detach it and there are gaskets involved. Thoughts?
 
Start with the putty knife scraper, and then add another. Drive them against the narrower gap. Then as you gain space, maybe a broad screwdriver. Eventually you may graduate to hardwood wedges. It will be a slow go, sp proceed with care and patience. If the drive shaft is stuck, trying to pull the powerhead will also get you stuck. If the bolt head is snapped, it is not holding your LU in place.
 
Start with the putty knife scraper, and then add another. Drive them against the narrower gap. Then as you gain space, maybe a broad screwdriver. Eventually you may graduate to hardwood wedges. It will be a slow go, sp proceed with care and patience. If the drive shaft is stuck, trying to pull the powerhead will also get you stuck. If the bolt head is snapped, it is not holding your LU in place.

Roger that. Will continue wedging and let you know how it goes.
 
OK, so I got the LU off finally. Lots of wedges and elbow grease worked it off. Took my time and it finally came loose. Turns out the spline wasn't holding it on, but the bolt that broke at the head was so corroded that it didn't want to slide through the LU hole even with breaking liquid. Got the remainder of the bolt out easily with pliers. What a mess inside however. Any restrictions to cleaning everything out with soap and water? Thanks for your help.
 
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