1957 Evinrude 35 HP thrust problems

[Win]

I have a 1957 Evinrude 35 HP Lark. I rebuilt the carb and tuned up the engine after it had been unused for a few years. It starts like a champ, engine has good compression and it goes into gear fine. In reverse there is no issue. However, in forward when you throttle up, the engine revs up, with little forward thrust. When you throttle back to idle, it puts along forward - appropriate to the throttle setting. What the potential cause / fix?

 

[joereeves]

Sounds like the hub of the prop is slipping.

Remove the prop nut... mark a line with a magic market on the bronze hub that extends into the propeller area. Replace the prop nut.

Now, run the engine with that marked propeller and encounter that problem again. Remove the prop nut and examine the mark you made. If it is now out of alignment, the hub is slipping within the propeller, in which case either have the propeller rehubed or replace it.

 

[Win]

Sounds like the hub of the prop is slipping.

Remove the prop nut... mark a line with a magic market on the bronze hub that extends into the propeller area. Replace the prop nut.

Now, run the engine with that marked propeller and encounter that problem again. Remove the prop nut and examine the mark you made. If it is now out of alignment, the hub is slipping within the propeller, in which case either have the propeller rehubed or replace it.

Thanks for information, It was the prop hub slipping. Replaced with spare prop and we're up and cruising at full speed.