Can anyone help me figure out what year my omc is?

I dont really have any experience working on boats as this is my first. It is a 120 hp gm omc, im guessing early to mid 80's by the colour of the 19.5 campion. It has a 400 leg and the previous owner has changed/updated parts on it. from what i can tell he only bypassed the original fuel pump and installed an electric, and converted the points ignition to electronic. Ive had issues this year with lack of power and high fuel consumption so Im trying to go through the fuel/ignition systems to try to pin point the problem but it is making things difficult for me when each time I go to get parts they can only point me towards what "may" work.Anyhow as i ramble the model number is 901110 and nobody in the area i live can tell me anything about an approximate year. Id appreciate any help at all...

Re: Can anyone help me figure out what year my omc is?

That is the model number for the verticle outdrive. Do you know the model number for the engine? That may easier to lookup. Unfortunately, I don't have a model application chart for pre-1986 drives.

Re: Can anyone help me figure out what year my omc is?

The problem is I only have the final 5 digits of the models 243s1...from what I can see in my manual it is probably a 79 select trim

Re: Can anyone help me figure out what year my omc is?

Is it an electric shift or hydro mechanical look for the distinctions there pretty easy to tell. could be either around 79.could also have been changed to a mechanical lower. Look for the anoed to distinguish. Information and pictures are out there to help,search how about pictures?