69' rude @ 5000rpm but slowing down!

[ryan04]

Hey guys. Quick questions on my 1969 55hp evinrude. when I'm at wot my rpms are at 5000, but then sometimes the boat will slowly start to slow down but the rpms stay the same. Before I know it I'm doing less than half my speed with the same rpms. It happened the other day on the water so I pulled the boat onto a bank and pulled the plugs out. They all had a little bit more than usual amounts of oil on the plugs. IT looked like maybe just enough to foul specifically #3 and #2. Once I cleaned them off and hit the water again it would be ok. Would that cause me to slow down? Even if it does why do my rpms still stay at 5000. All that aside the motor runs good. Any thoughts?

 

[OBJ]

Re: 69' rude @ 5000rpm but slowing down!

Check the prop hub Ryan. Might be slipping. Easy to check....put a reference mark from the rubber hub out to the metal part of the prop. Use some marker that won't wash off in the water. If the engine does it again, check the reference mark. If the mark on the rubber bushing is not lined up with the metal on the prop, the hub is slipping. The prop can be rehubbed if that's the problem. Or swap off the prop with a known good prop and see if the problem still happens.