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BF225 - Lower Unit Driveshaft Spline Engagement Issues

brettmarl

brettmarl

Regular Contributor
So following on from my lower unit saga.... starting with the cracked bearing I finally managed to get all the parts I needed, rebuilt the driveshaft, and rebuilt the propshaft stack into a new propshaft housing, re-assembled - everything looking good.

When to install lower back on motor - and for the life of me - I can't get the drive-shaft spline to engage. I've done this procedure dozens of times with water pump services - always needing to rotate slightly to catch the spline - then things slide nicely onto the bolts.

Now, the very tip of the bolts catch the lower unit case (maybe 3mm) - but the spline won't go any further in. Not catching on the water pump or gear selector - as I still have about 1 1/4" left to go!

Tried in neutral and tried in gear. I can feel it catch and once it catches, I can no longer rotate the drive shaft via the propshaft (in gear), which is expected.

Decent amount of grease on the spline. The honda spline-holder tool (same female pattern), slides on perfectly with no blockages or scratches.

I used a pump sprayer to dump a load of alcohol into the female end of the spline in order to flush out old grease - didn't help.

My first instinct was maybe bent the driveshaft when pressing the new bearing on. I inspected this closely visually, doing a full rotation with a zip-tie barely touching the spline. It looks fine - full rotation within at least 1mm or less. Would expect a significant deflection to cause binding.

Don't want to force it - and it's so heavy and awkward. Wondering if any one has ideas. My worst-case scenario is to disassemble things again and remove the drive-shaft so I can try inserting it without the rest of the lower on; but really don't want to go there :)
 
Are you positive it's hanging on the splines and not somewhere else in the ex case? Could it be that famous bushing?
I might try banging it upwards to see if I could get it to leave a witness mark up there. Then pull it out and use the brightest torch I have to see up in cave.

If you're sure it's the splines, could you maybe set the lower on a floor jack pad and get a helper to balance it there for you while you manipulate and guide the shaft? I know from stabbing big rig truck trannys the splines sometimes want PERFECT alignment or they fight back.

Another thing I've seen is the splines get worn in to each other and you will have to try rotating the shaft one splines at a time until you find the sweet spot. When you do, it will slide in like buttah.

Having it on the floor jack can help a lot doing that.

Just some ideas.

Good luck.
 
That center-span bushing is a good theory... this is the one with the cir-clip I can access from the bottom? Maybe I'll try taking that out and see if it goes in then. Lower has been off the engine for a few months, is it possible that thing swelled up a bit?

From witness marks on the spline-grease, I can see that the spline engages for the first 1/2" or so just fine, so I'm pretty sure it's aligned right. This is my newer 225 (~700hrs) and both this and starboard have always gone in easily before, but the lower has never been off for more than a few hours.

I like the idea of a jackable platform also, although I'm afraid to put more than hand-pressure on it - as if I damage the engine-side of the spline feels like I'm in a world of hurt :)
 
Mystery solved. Driveshaft bushing was just packed with salt on the outside pushing the rubber in right. Guessing two months of drying out made it worse.

Pulled the circlip and washer and Lower goes in super easy all the way.

I mangled the circlip pretty bad getting it out. Anyone tried running without this bushing? Meant to be a vibration reducer.

IMG_5319.jpeg
 
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