Tough-Steering Pontoon

My M-I-L’s got a roughly 10-year old Northwoods pontoon w/ 40 HP Merc on it. It’s pretty bare bones. This year, the steering has gotten really stiff. I’m not aware of any damage, though I haven’t gotten a chance to inspect things yet. My thought is that it might need a new steering cable. Is there anything else I should check first? Any definitive way to know if it’s the cable? How easy/hard is that to replace?

I have the same pontoon. While my steering has not gotten stiff I did recently have to replace the throttle cables for that reason.