175 is not a foot pedal hydro and no RIO. Speed control is a lever on the fender deck. No RIO is one of the reasons I kept my 1988 185.The switch that might be hiding between the frame rails is the switch for sensing if you're stepping on the reverse pedal. I don't know if the that was a thing in the days of the 175 or 185. Do those models have the engine kill if PTO is on and you try to move in reverse without operating a yellow button or switch ("RIO" it's called)?
No not yet it’s on my list to check, I’ll let you know the results, thxThe only switch under the fender deck on my 185 is the neutral safety switch that makes you hold the brake pedal down to start it. The only safety I recall that affects the PTO is the seat switch and you’ve already ruled that out. Have you inspected the PTO wiring for a chafing short? I’m also wondering if maybe the voltage regulator fried and the PTO is dragging down the electrical system when engaged.
I wouldn't have expected another "PTO/Safety Switch" hiding somewhere without the RIO. But I guess that's how it enforces the safety rules on that model. Interesting! I'm only familiar with the newer stuff that uses a set of relays (100 series) or the ECM unit (X300+).And then again I could have been wrong. The PTO safety switch may be the one hiding under the fender deck. I don’t remember this one but the last PTO wiring gremlin I had was on my 160 about 20 years ago. I don’t know or remember where this PTO switch lives.