motor up or down?
 

I know this is probably a dumb question but here goes...I have a 19 foot boat on a mooring in fresh water. It has a 115 horse outboard motor on it. 2 stroke Mercury. When on the mooring should I leave the motor down, or lift it (with the hydraulics) so it is out of the water. I can't seem to get a straight answer from my local marine guys. The plus of it being up is that it won't get zebra mussels and algae, but I worry about all that weight straining the transom. Also I worry oil will leak from the oil mix tank (it has a tank for 2 stroke oil that gets auto mixed with the gas and when up the oil is against the cap).

Any thoughts appreciated.

up in summer, down in winter

Up. The transom is designed for the weight, I would venture to guess the oil tank and cap is also designed not to let any product leak as long as the cap is secure. You could always put a oil absorbent diaper down if you are concerned with leakage. Trailering the boat with the motor up is more stress than sitting static in the water and that's no problem.

If its a local secure lake/pond.... and you are not worried about the prop getting pinched then there is no reason you could leave it up. If growth is your main concern and you run it every three four days through out the season then down would be no problem either.
Just my opinion and you know how that goes....
sol...

appreciate the thoughts, thank you. I'll be leaving it up.

I have the same engine, in fact have had 2 of them... as others said.. leave it up... as far as the oil leaking.... replace the "O" ring on the fill cap.. after a few years they get hard and tend to leak no matter how hard you crank the knob...also check the vent and check valve.. they have a nasty habit of falling off when you replace the cowl..