Re: 125force ?
Force 1258x3a is a circa 1983 Enigne.
Early Force engines were basically re-badged Chrysler units. Later on, Mercury bought Chrysler, and presto chango, the Force inherited some Mercury bits.
I have a 1988 125hp, and I am VERY happy with it. The reputation that precedes Force is unfounded. Mine is as reliable as any outboard- its just I choose to take care of it

I am happy that I can tune my own boat, change my own waterpump, and do my own maintenance without going to a mariner. I have never had a problem getting parts, either second hand or new- thanks ebay and iboats
First, do a compression test on all 4 cylinders and post the results. Buy yourself a waterpump kit complete, and chage it. To change the waterpump, you need to drain the lower unit oil ( makes it lighter), so change it as well.
Buy yourself a workshop manual- I reckon the Clymers is the bomb.
If compression is good, and you change thw waterpump etc, then go from there.
Cheers