U4EA;
        It is fortunate that you found the problem with the crack. If the boat is stored near navigable water, it is suggested that you give it a temporary tack weld in case of an emergency. This is very important: the engine can only be run at very low power with the tack weld -- anything more will get you about 1000 yards from shore before the weld will give way, snapping the engine around with more than enough force to rip the remaining mount completely off the boat.
Such an accident would leave the boat adrift without an engine so I suggest you install an emergency oar on a special mount. Drill a hole through the bottom of the hull to accomodate a length of 4" drainpipe. Only enough drainpipe needs extend below the hull to accomodate a 4" drain cap in which you drill a 3/4" hole. Do not glue/epoxy the cap to the pipe -- also drill a 3/4" hole in the shaft of the oar, then insert an extra long 3/4" bolt or threaded rod through the pipe cap (securing it to the cap with a nut on the inner side) up through the pipe and then through the oar, tightening down tightly a nut on top of the emergency oar, which will hold the oar in place as well as keep the cap tight on the outer hull side of the pipe. Then label the oar with instructions to remove the nut for emergecy use and pound the bolt down into the shaft hole to more easily remove the oar from the bolt. Then attach, in whatever means, a wrench to the oar.
Now, well before your wife's time to 'go out with the girls', or whatever, take off from home and, if possible, block the road in. Park the car off to the side (bump into a tree for good effect) and walk back to the house. Make sure the boat is docked in the water and alert your wife to the roadblock and the fact that you're heading back to the car and heading to the repair shop (if she hasn't a wrist watch and you're unobserved, turn the clocks ahead about an hour). By all means, let her know that you're not leaving her stranded -- if it's such an emergency that she thinks she really needs to leave, she can use the boat -- no need to tell her anything but how to get the engine started -- but you will be back as soon as possible (we suggest you not return until late in the morning).

PS I should warn that if you meet your living, breathing wife the next morning, she's probably going to be as mad as a wet hen -- but accidents are accidents.