Mercury 50 outboard problem need help

[frankji]

Hi, hope someone can give me a clue about this problem.
I just had the powerhead of this 88 merc 50 2 stroke rebuilt.
The engine starts well and idles well. It has new plugs. I can toot along at low rpm and move my 17' slowly. The problem occurs when I try to et some speed by advancing the throttle over 2500 rpm, the engine speeds up but no power seems to be going to the prop - so the boat goes nowhere while the engine rpm keeps going up.
I should also mention that I had the water pump serviced before the powerhead rebuild - but no other lower end work was done. Any ideas gratefully accepted!
thanks in advance

[Mark Cahill]

I definitely suggest having the mechanic that did the rebuild take a look at it. You no doubt paid a good bunch of dough to get it done, don't be shy about making sure he tested his work thoroughly. It's generally implied that he'll provide a working motor. Also, they can't always test everything in the tank - often problems with no power can't be diagnosed until the engine's hanging off the boat.

Just my $.02

[Frequent Fly-er]

If the motor checks out ok, it could be a spun hub on the prop. To check this out just replace the prop with your spare and test. Common Merc problem.

[frankji]

Frequent-flyer:

The problem was indeed a spun hub on the prop. Spare prop worked OK. Only evident on hi-torque. I could not get it to spin manually.

Thanks!!