Speed of 20ft Crestliner w/70hp Yamaha

[branman1971]

Re: Speed of 20ft Crestliner w/70hp Yamaha

Ok, when I get the spare money i will go to an 11P prop and see what she does. I also noticed that i get more speed with the motor trimmed all the way down. When I trim up I start to lose speed and I can only trim up a very small amount before i start to hear and feel slippage of the prop. It seems to run better just trimmed down. Make any sense?

 

[steelespike]

Re: Speed of 20ft Crestliner w/70hp Yamaha

There is so much turbulence with a toon any trim setting wouldn't be surprising.Not sure why we ended up with a 13 a 2 inch decrease in pitch typically nets about 400 rpm.increase.As you sauggested your better off at 5,000. Was the 5,000 with 4 and gear?

 

[branman1971]

Re: Speed of 20ft Crestliner w/70hp Yamaha

Was the 5,000 with 4 and gear?

Yes, it was with 4 folks, and about 10 gallons, a full cooler, pretty decent load but not slammed.

 

[quantico]

Re: Speed of 20ft Crestliner w/70hp Yamaha

Read my answer to top speed for a bentley in the pontoon section here ... hopefully some of that info will help you understand why you are getting better speed with the engine fully down. ( which is normal )

 

[VaGent]

Re: Speed of 20ft Crestliner w/70hp Yamaha

I"m unable to find a listing for my '87 Johnson 70hp VRO which I have on a 20ft Riveria 'toon & running a 13.75X15 prop. I will be using 2 batteries along with 22 1/4 gallons of gas with only a bench seat across the back so the weight should be very light. Can you advise me as to what size prop would be best for this engine & what kind of RPMs I shouldbe running? I don't have a tach on it at this time but I will have in a few weeks.

I have been reading all the above posts & am starting to learn a lot but right now I don't mind saying I am totally confused. Thsi is my first ever 'toon & I sure don't want to mess up the engine by using the wrong size prop. Looking for a good "all around" prop for crusing & "putting around" most of the time.