Mariner lower unit crack near prop/exhaust hub

Hello folks, I recently hit something and messed up my prop. The hit took a small piece about the size of a half of a quarter out of one of the blades, which certainly threw the prop off balance. Later on I found a 1-1/2" or so crack in the lower unit. I don't think it was there immediately after I damaged the prop, but it may have been. Or could it have been caused by running the engine with an off-balance prop causing excess vibration? What do you folks think, how serious do you think this crack is and should I be overly concerned about getting it repaired immediately? Of course, I'm getting a new prop before running it any more.

Thank you for any input you may have.

Below is a pic showing the area of the crack in red. This lower unit is not my lower unit, but it's similar and shows where the crack is.

Re: Mariner lower unit crack near prop/exhaust hub

jdub2 said:

caused by running the engine with an off-balance prop causing excess vibration?

Click to expand...

yep

Re: Mariner lower unit crack near prop/exhaust hub

Anyone have any experience with repairing this sort of thing? Will this crack still tend to get worse with a new balanced prop?

Re: Mariner lower unit crack near prop/exhaust hub

drain your lower unit, if it comes out milky you probably already contaminated your LU oil. Im thinking the LU gears are whats damaged from the impact. If not just throw another prop on JB weld the crack and feel for vibration on your next outing...

Re: Mariner lower unit crack near prop/exhaust hub

The area of the crack appears to be behind the seal on the gearcase. If so, the gear oil should be unaffected, but check it out. if it is OK, seal it with some epoxy putty, and forget it. If not, consult a good welder....

Re: Mariner lower unit crack near prop/exhaust hub

Be very careful as this is where threaded area is that cover nut screws into. If the crack expands the nut could jump the threads in a high reverse thrust event..yanking carrier,cover nut,prop shaft and prop into the deep six, seen it happen several times.

Re: Mariner lower unit crack near prop/exhaust hub

At this point a good prop shop can weld that up, chase the threads, and with a lil paint, you'd never know it.

Let it go, and see the above said destruction scenario play out.

Re: Mariner lower unit crack near prop/exhaust hub

Thanks guys for your input. I was looking at a shop manual and I think I see what you're talking about regarding the threads. I guess the right thing to do is to bring it in and get it fixed properly. I just have to chalk it up to experience.