Johnson 140 V4 Cavitation ?? Help

[heavydem]

Hi all, I have a Johnson 140 and am at an end with this problem. When I throttle up to get out of the hole, the engine over revs and I go nowhere. The prop is still turning but I am barely moving. If I ease on the throttle from neutral, and get on plane slowly, then I can run no problem. If I am pulling a tube and turn sharp, it does it again. People are telling me it is cavitating and my leg is too short?

1. I have had the lower leg inspected and rebuilt. No wear or gear issues found
2. Added a 'dolphin fin, no change.
3. Prop hub is not slipping
Any help would be appreciated. anyone tell me how long theirs measures if they have a 140 ?


thanks for any advice.

[Solarman]

Can't tell from pic if 2 or 3 blade prop. If 2 blades it is a speed prop, notorious for bad hole shots, but top speed great, though it does have cavitation problems. Can borrow a 3 blade sometimes to try/test, just don't over rev motor, past 5500 RPMs.

if 3 blades, check level of cavitation plate, it should be at, or slightly below bottom (no more than 1/2” above) of boat? If motor is at lowest bolt hole, you may have to buy a hydraulic jack plate assy, and remount to get lower, or invest in parts for longer/deeper foot, and raise motor accordingly.

A jack plate may cause tilting problems unless raised up first, and may require longer cables and wiring for motor if not enough slack to move motor back for adding jack plate unit.

Good luck.