1978 Mercury Black Max, kicks out of gear or something. Help!!!

[Bohunter21]

Today I took my 1978 HydraSport With my 1978 Mercury 150HP Black Max out on the river for the first time this year. I have owned this rig for about five years and have never had any serious problems with it, until today. I'm not to sure if this is serious or not and I need a little help identifying the problem. We had been on the water for about five hours (not catching any fish) so we decided to head for home. I was running a little harder than I usually do, cranked her up to around 5500 RPM's and was cruising when all of a sudden it acted like the engine went into neutral, the RPM's went high and the boat lost all power. I immediately let off of the throttle, let the engine idle a few seconds and then put it back in gear. All seemed well until I got the RPM's back up and the same thing happened again. I didn't want to take the chance of getting stuck a mile down river from the dock so I put it back in gear and ran it at about 2000 RPM's back to the dock. When I got home I pulled the prop to check the fit and look at the splines. There was a little play but not enough to allow this kind of a slip (as far as I could tell). This thing acted like if you were racing down the road in your car with your foot on the gas and put it in neutral at the same time. Do you have any ideas what would cause this?
Thanks for your help.
Bohunter......

 

[Bosunsmate]

Re: 1978 Mercury Black Max, kicks out of gear or something. Help!!!

It does read like a prop slip.
Mark the back of the bushing with a straight line across it and onto the prop casing and have another run with it.
If that line does not keep straight across the bushing/spline and onto prop casing it is a spun prop bushing.
If its the gears on those it normally makes a bad noise going into reverse

 

[Bohunter21]

Re: 1978 Mercury Black Max, kicks out of gear or something. Help!!!

Re Bosunsmate, you were right on the money. I did as you suggested and after the run the marks were misaligned. I am happy this is all it turned out to be. Thanks for your help.
Bohunter....