is my motor cavitating? pulling more air than water?

[tholdah]

We just upgraded from our very underpowered 35HP to a 70HP on our 17' jon boat. We had to raise the transom 4" so that the cavitation plate would be 1" below the bottom of the boat (which is what was recommended everywhere I researched). When we power it up and try to plane out, it's like it's slipping. I would desribe it like a clutch slip in your truck. I was told that it's cavitaing or sucking air?

 

[huntinfool]

Yes that is what it sounds like. 4" is probably not enough raise on the transom. I would put the cavitation plate even or even up to one inch above the bottom of the hull.

 

[Quackrstackr]

Could be cavitation, could be a spun hub or it could be vents that are too large (if your prop is so equipped).

 

[huntinfool]

I assumed when they said they upgraded that he meant new power. It could be a spun hub if it is a used motor.

 

[tholdah]

I assumed when they said they upgraded that he meant new power. It could be a spun hub if it is a used motor.

The motor is an 88 suzuki. the only thing we did was tune it up and put on a new prop.

 

[Quackrstackr]

Do you still have the old prop?

I would swap them out and take it for a spin before I started moving the motor around.

 

[stinkynathan]

Could be cavitation, could be a spun hub or it could be vents that are too large (if your prop is so equipped).

Excuse the pedantry here, but...

....wouldn't that be ventilation, instead of cavitation?

https://www.boatinglife.com/article/Maintenance/Ventilation-vs-Cavitation-The-Facts

 

[Quackrstackr]

At this point, it could be either.

My last ski boat was prone to cavitation. It would burn the paint off of the prop.

 

[Specknreds]

You can also try a 4 blade or have someone cup your prop for more bite.

 

[rick50]

I would defininately try the old prop first.