Mystery Problem

[Jtgator]

Just bought a used a 2005 50 hp 2 stroke Merc on a 20 ft pontoon. The engine will not rev past 4000k RPM at WOT. Max WOT should be closer to 5 to 55k. Taken to 2 diff mechanics and cannot figure out problem. No water in ntoons,,firing on all cyls, correct prop, engine runs great just will not get up to speed....Only thing I have had done prior was reseal lower unit. Any ideas ??? This is a real head scratcher since it runs perfect except for low RPM at WOT. Its at Marine Max now and cant figure it out either.

 

[Grub54891]

Did you actually run in tge correct rpm range before the re-seal? Or has it been this way since ya bought it. Is there to much pitch to the prop? It may have preformed fine on a boat,but on a toon the setup is different. I swapped out a motor from a different boat,it preformed perfectly on its old setup. But once on my boat it had to be re-propped from 17 to a 15 to get tge proper rpm's.

 

[Jtgator]

I bought boat without water test. I did not try it out because it had water in lower unit. Dont know how it ran before re seal. Mechanic says prop should be O.K, I think its a 10 " I don't know the pitch.

 

[Barnacle_Bill]

Do you know if the tach ever read correctly? Look on the back of it and make sure it is set at 6P.

 

[Faztbullet]

1) either propped wrong 2) tach reading wrong 3)gearcase swapped out and wrong ratio