Evinrude E-NATION, for those dedicated to water, power, fishing and fun
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Skipper
Posts: 12
Registered: ‎07-16-2017

Should I try a different prop?

Not surprisingly, I am loving my new 115 H.O., which is a huge upgrade from the original 2005 Honda BF 90. It's a whole new boat.

 

With respect to props, we started with a 17 pitch Viper. It was pretty obvious from the outset that we needed to go with a higher pitch. I could easily hit 6000 RPM under a variety of conditions. I could sense that I was hitting the rev limiter and still had some throttle left.

 

Now we're working with a 19 pitch Viper. I couldn't test it right away at WOT due to sea conditions but I finally found some flat water yesterday. It was just me and a full tank (29 gal), which is pretty much my normal load. I monitored RPM on my Garmin via the NMEA2000 interface, which I assume comes right off the EMM. I found the digital data was 100-200 RPM higher than what my System Check tach was showing.

 

On two runs I was able to eek out 5900 fully trimmed up -- maybe with a bit of a tail wind. On other runs I could regularly hit 5800-5850 irrespective of wind direction. From what I've read here and elsewhere that's still a little high but am not sure if it's worth trying to dial it in further or if I should leave well enough alone.

 

The 19 pitch gives me a pretty comfortable 4000 RPM crusing speed and it appears my mpg has gone up some (up to 4 mpg in calm conditions). I have plenty of top speed (about 38 mph) and the hull I have gets on plane very quickly. But, although I'm not 100% sure I'm calculating it correctly, my prop slip seems to be in the high 20's at WOT. (I have a fair amount of wind resistance since it's the Maritime model with the pilot house, so maybe that's normal?)

 

Do folks think I should try an even higher pitch? My overall goal is to dial it in for crusiing efficiency more than anything else.

 

Thanks in advance!

Admiral
Posts: 8,432
Registered: ‎07-14-2011

Re: Should I try a different prop?

 

 

Does your motor have the V4 or V6 size gearcase? 

 

The Viper series is good for speed but not the most efficient at cruising speeds. You may want to try a Rogue if you have the V4 gearcase - 13 spline shaft - or a Rebel with a V6 gearcase  - 15 spline shaft.

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.


Skipper
Posts: 12
Registered: ‎07-16-2017

Re: Should I try a different prop?

Thanks Bill.

It's the 20-inch so I believe it's the V4 gearcase?

Model A115SHLAF
Serial 05492584

If I try a Rogue should I back off on pitch or stay where I am?
Admiral
Posts: 8,432
Registered: ‎07-14-2011

Re: Should I try a different prop?

 

 

Start with the same pitch as it should come out close to the optimal rpm range. It will be trial and error.

 

 

 


"There is never just one thing wrong with a boat";
                    -- Travis McGee, main character in a book series by John D. McDonald 


 



***************

The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.

The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.


Skipper
Posts: 12
Registered: ‎07-16-2017

Re: Should I try a different prop?

Thanks, as always, for the quick response.