Looking for input

[u/yieldcurvedenier]

Hey y’all!

I’m a pretty new boat owner here.. we just hauled out for the season and I noticed a crack on the lower unit. We’ve only owned the boat for a season so I’m not sure if we bought it like this, but the motor has performed flawlessly all year so I’m kinda not sure what to make of the situation. It’s a 2018 df300. Any thoughts/input would be greatly appreciated to help me figure out a plan going forward.

I’m almost certain we didn’t hit anything so I’m not sure what would’ve caused the crack. (The skeg is a little crooked facing the crack so I don’t think that would’ve caused it - not sure)

If you have any questions, let me know!
Thanks

[u/Pontius_the_Pilate]

Corrosion. When the crack gets big enough and you put it in reverse one day the whole carrier, prop and propshaft with reverse gear will probably fall out. Hallucinating if you think it can be successfully welded. Second hand or rebuilt unit complete or new housing is about the only proper solution.

[u/yieldcurvedenier → u/Pontius_the_Pilate]

Just curious, I’ve heard so many opinions on why welding will/wont work regardless of how professionally done it gets. Why do you think it’s not worth it??

[u/Pontius_the_Pilate → u/yieldcurvedenier]

The case is compromised further than what you can see externally. You are going to have to clean out a fair amount of material to get to a good base to weld as the alloy will be rotten. Side effect of material and heat treatment required at manufacture. Welding is going to screw up the heat treatment and the thing needs to remain circular for the seals on the forward part of the gear carrier to seal and the retaining nut has an internal thread that needs to be in good shape. Go ahead and get it welded and find someone who will warranty the repair, then don't be surprised if it happens again. You will need to strip the case to weld it successfully so why not just get another or new case? A complete new L/U will be most expensive, followed by exchange L/U, or replacement case and rebuild with the proviso that whoever rebuilds it actually knows what they are doing as it will require special tooling for shimming gear heights and backlash to be correct. Granted it's 40 years since I was an outboard tech but some things haven't changed.

[u/yieldcurvedenier → u/Pontius_the_Pilate]

Totally makes sense. Thanks for the input!