Considering the info above, with my specific engine and prop, am am I hurting my motor using the 20 Raker on my 1979, 70 hp Evinrude? Will running a premium grade of gasoline help if I continue to run the 20 Raker?
Thanks for the good explination for the reasons for having the correct prop.
be beter if you started your own post. but wot rpm must be within reaonable limits to achieve maximum motor life. 93 octane is not the idea. the best gas is 87 with little or no ethenol. it is a 79' omc not a 2009 nascar. what is you wot rpm?
I currently have a 17 OMC stainless prop and a 20 Raker. The 17 will run 34 at 5600 rpm and the 20 will run 35 at 4900 at WOT. I have been told the '79 model has a lower rpm rating (5000) than new 70hp hp motors. It is had to get anything other than gas with 10% ethenol
I'd go with Jr's suggestion and work the set up to get the most out of the 20 Raker before buying more props. Going to octane higher than 87 is not recommended.
Thanks for the information guys. I will certainly take your advice. My anti- cavitation plate is currently setting even with the bottom of the boat. It is in the second hole from the top. What would you recommend as a starting point for the correct height? Should I go up one hole to begin with or two??
i would go one hole at a time untill blow ouit occurs with trim half way up. and id run that motor at 5500. the 17 is closer than the 20 at this point. maybe the 20 will come around with raising motor.
