Hi...I have a 1979 50hp Johnson SeaHorse, model # 50RL79C, on a 15'
Hourston runabout. It's been running strong lately, no problems at all. I
took it out yesterday afternoon, and suddenly it is churning the water and
not much else at WOT. Its moving as I would expect at low throttle, but when
I throttle up it doesn't go much faster. The bow of the boat porpoises
upwards, ands thats pretty much it. I'm figuring the bulk of the extra
thrust is coming just from the exhaust. I've tried a couple more times since
then, same result.

The motor is fine, shifting in/out of gear is fine. The only thing I can
think of is that the rubber is slipping in the prop hub. I tried having
someone hold the flywheel still while in gear, but I couldn't make the prop
slip on dry land. I don't see any signs of shredded rubber or anything
either, but I'm guessing I probably wouldn't anyhow. I know I can't put the
kind of torque on it that it probably gets in the water at WOT either. The
propeller is older, and was going to be replaced this season, so...

Does this sound familiar to anyone? Am I correct in thinking its the hub
slipping? I cannot see any kind of a clutch in the exploded diagram of the
leg, so I'm thinking thats the only possible place for slipping.

p.s. None of the weights in the boat have not changed, nor has their
location. The bilge is bone dry, nothing is dragging, and the motor is
indeed aligned correctly with the keel. No rocker or hook in the keel
either.

Any tips or advice would be greatly appreciated, thanks!