Shipyard Isl. Marine Engine Parts - Plugs fouling

I have a 1987 excel 225 that was rebuilt in '03. My plugs fouled up with oil so I changed them out. I ran a few minutes and it seems to be missing again. I guess it fouled up again. I premix my fuel and have been running 50 -1 wit yama lube and ring free 1 oz per gallon. I premix as I don't have an oil injector system. Should I be using a different mix? Or is it something else? Out lobstering with the family so any help would be appreciated.

One other thing to mention is I didn't use a torque wrench to tight the plugs. Tried the quarter turn after tight. Probably did it less than a quarter I was afraid to strip it. Could they be too loose? More history. Got boat a few months back. Ran good. Starting missing. Changed the plugs and decarbed. But changed nefore running rhe seafoam, so i thought that could have messed them up. Put new plugs in (again without torque wrench). Ran good for two days then started loosing rpms and seemed to be missing. Plugs were oiled. Put new ones in and that didn't make it ten minutes. If it is a "tighten" issue, what should they be torqued too if I go buy a wrench? (yes, I'm typing this in on a lobster reef with my phone)

Its hard to say whats going on. You need to explain "its missing" a little more clearer. As in when its missing rpms wise and is it just shaking more then usual or is it surging up and down in rpms.

Andy

Sorry. Really bad typing on my phone. I am editing my post to try and make it more concise and less
Scattered.
Plugs are real oily when I remove them (most if ot all). black too (all)
The motor bogs Down and loses Rpms at high speed or heavy load (7 -8 people)at a lower speed or rpm. After doing the up down rpms it settles down to the lower rpm with a throttle position that should get more rpms.
New plugs, fixes it until the same senario is reached again.
Pretty sure if I was by myself and low on fuel, it would scream all day.

I assume, since I premix, extra fuel is entering spark plug chamber Due to a fuel pump/ carb issue or not enough spark is being produced; and it can't be burned as fast as goin in? The oil is then remaining on the plug when I pull it.

I likely will bring it in to my local Yamaha as I am not sure I can properly diagnosis or fix. Money tight though.

Revised above post