Re: mercruiser outdrive disengaging under load?
Don's the expert, so I will tell you what I know but it's not gospel. Always be careful not to hurt anyone when working on the boat.
I did lose my coupler recently. As Don said, it spun once and was gone. Once I got the boat home, I confirmed it was the coupler. I DISCONNECTED THE BATTERY CABLES (!!!!), put the drive in gear and worked my hand down the back of the engine, over the coupler to where two fingers were on the sterndrive yoke driveshaft. I had my kid turn the prop in the direction it was in (ccw, as I recall). I could feel the shaft turning and the coupler wasn't turning at all. Now my case may be different than others--the aluminum splines on the inside of the coupler were sheared off. If they were partially gone, or if the rubber part was failing, then turning by hand might still turn the coupler, but it may slip on the lake under load.
On your prop--I had the EXACT same problem for my first season or two. The prop was just "blowing out", losing its bite on the water, especially under load of tubing or wakeboarding. The two or three props I got with the boat from the previous owner were all too low of pitch. I was lucky--a local boatyard let me take one refurbished prop out at a time--as long as I returned them in the same shape, I didn't have to buy them. I found that a much higher pitch worked a lot better but still blew out on high speed turns. I eventually found an in-between pitch that hardly ever blows out, only on rough water at high speed and usually in turns--and I don't do all of those together very often. Finding that prop pitch was like getting a new boat.
Hope you get it nailed down!
