Viper or Raker Propeller?

[SteuryLover]

If I am trying to correct a slight cavitation problem due to I believe outboard mounting height. Here is a quick question.

What is the difference between a Raker and Viper prop?
Which of the 2 will reduce my cavitation issue and provide more grip is rough seas?

I usually go 15 miles min offshore for fishing grounds, MPG is important to me, I know I want to stick with a 3 blade as I do not want to loose too much RPM. Currently running a 13.25x17 QL alum prop. 18' v hull 1500lbs with motor center console. I am getting approx 5k at WOT with the current setup @34knots with a light load. The boat is used for fishing only and loaded with an additional approx 1065 lbs on top of the boat weight of 1500 lbs including outboard. Thats a total of 2565 lbs while underway with a 1993 Johnson 88SPL. ALL opinions are appreciated. I have done some research and do understand the basics of prop design and sizing. Thanks for everyones help.

 

[Dhadley]

Re: Viper or Raker Propeller?

The little Vipers and Rakers are made to do different things. I'd think that in an offshore situation like yours the Viper would be a better choice between the 2 three blade props you've mentioned. The low top rpm is a concern to engine life.

Do not assume you'll always lose rpm with a 4 blade prop compared to a 3 blade.

 

[SteuryLover]

Re: Viper or Raker Propeller?

Thanks, you mentioned I may need to actually raise the motor more with either of these props. Currently the motor is mounted one hole below the top, so I have one more hole to work with to raise it. The current QL prop is brand new, and has a small cup. I will test it out one more time when the weather calms to see if I still have the issue. My first test was in 20kt winds and 4-6ft swells. I could not leave the break wall and even behind that it was pertty bad. Is there a basic SS prop that may help? Do you recommend going down to a 15 pitch or 17 SS to get RPM up? How about a 4 blade aluminum? Thanks for your time.