very hard starting 85 hp

i just bought this boat,motor sunday. the motor did start but took some time. in the back yard it wanted to start with help of the starter but did stay running after 10 or so trys. it is a 1977 merc 850. he said he was using a 30:1 oil mix. what i have read it should be a 50:1 oil mix would to much oil make it hard to start ?. i think there is a few other issues why it's hard to start also. just haven't got to look at it yet. i have not done any work on it yet. pumping the primer bulb did not seem to help much. out sides of carbs were pretty dirty . might take a look at fuel pump. one other question this motor have a tilt switch on the motor some place if it does haven't found it LOL if not is it much of a deal to put one on the splash well. he also said he needed to let it idle for a 1/2 hour ???? after that it runs very well. that don't sound right.that don't sound right. there a thermostat in this motor? i will clean all the wire contact places. good idea to use electrical grease on connections ?

Re: very hard starting 85 hp

first off how old is fuel, more than a month or two old forget it, get new gas, and if you can drain carbs and while screws are out pump some new fuel through carb to flush things out. running it at 30:1 won't really make it harder to start just smoke more and is uneeded. i would recommend 50:1, is primer bulb getting hard? i give mine a extra pump after it's hard to force a little gas in when cold, also check to make sure choke plates are closing and closing all the way. if this all fails put some premix in a spray bottle and spray into engine like starting fluid, if it kicks right over runs a bit then dies you may be looking at cab overhauls, yes it should have a t-stat. they are inexpensive and should be changed regularly especially in salt water use. but even without one it shouldn't take a half hour to run right, sounds more like carb issues, you could try running some seafoam through if carbs aren't to varnished, but beware a lean running engine will fail prematurely.
p.s. free advice change the impeller and lower gear oil pronto, good luck