1974 Johnson 70HP

[psm99]

While on the lake last weeked

While on the lake last weeked motor starting "spinning" out at higher RPM/throttle.

Ideas how to start figuring out problem?

 

[galamb]

Spinning out?

You mean rpms

Spinning out?

You mean rpms increased but boat slowed down?

 

[psm99]

Motor roared when increasing t

Motor roared when increasing throttle. Ran fine in idle and lower speed.

 

[jwbmarine]

try another prop......

try another prop......

 

[galamb]

"Yes, prop hub is "spun&#3

"Yes, prop hub is "spun".

The inner hub has a rubber sleeve around it and both are pressed into the prop.

It's designed that way so if you hit something hard, the prop will spin, hopefully saving the blades from severe damage. But as the rubber gets old it loses it's grip and starts to slip - at higher speeds at first and then progressively worse.

The hub can be replaced, but it's not a "do it yourself" project - most prop shops charge about 50 bucks or so to press in a new hub..."

 

[psm99]

"galamb,
Thank you for the de

"galamb,
Thank you for the detailed explanation makes sense. Could have been deteriorating all along and last weekend was the final straw."