22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

[ShellBack101]

I have a 22' Crest XRS, with a 2007 ETEC 115, 13 7/8 x 11 pitch prop. The boat gets up to 5700+ RPM. but only gets 18-19MPH (GPS). According to Evinrudes performance tests on their website this size boat / motor combo should be closer to 30MPH. Anyone have ideas on what is going on?

I marked to prop and hub to see if the prop was spun and that appears to be fine, I am not sure what is going on, any help is appreciated, or if you have a similar set up, your performance numbers would be helpful e.g speed & RPM.

 

[craigmack]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

I guess a few questions need to be answered... prop condition and motor height?

 

[Silvertip]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

There are lots of factors to consider when trying to figure this out. How high si the engine mounted. For starters, it should be placed full down on the engine pod. Outboards run in very turbulent water and if the engine is mounted a bit too high, the rpm may be ok but the prop has a great deal of slip due to aeration/ventilation. If it is already mounted as low as possible, then look for something on the bottom of the boat that is disturbing water flow between the tubes. If that's ok, experiment with trim. There may be a spot where the prop hooks up best. If that doesn't work, then one might suspect the prop is wrong for the task -- meaning the prop is intended for a V-hull (planing hull) rather than a workboat/pontoon. Pontoon/workboat props have large rounded blades. That style of prop in either a three or four blade would work best for you and also provide better thrust in reverse. Pitch seems about right but for some reason the prop does not seem to be hooking up (way too much slip). One last thought -- make sure the tach is accurate.

 

[rogerwa]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

Just for comparison, I am pushing a 25' pontoon with a v4 Evinrude 115 using the OMC Hydra 13P prop. I get about 5200+ RPM and about 25mph. The hyrdra is made for toons with bigger blades and cupping on the blades.

You may try a 13p prop and see where you are at.

 

[craigmack]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

Could it be a rev limiter is being reached? If so then I'd say the pitch is definitely too low.

 

[Old Screwball]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

I was going to say pretty nearly the same thing. My 75 came with a 13 pitch. I could get 5700 rpm, but not at WOT, the rev limiter stopped the revving. Put on a 15 pitch, now at WOT I'm spinning 5500 rpm and 24 mph.

 

[Silvertip]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

Could it be a rev limiter is being reached? If so then I'd say the pitch is definitely too low.

The rpm band for that engine is 5500 - 6000 rpm so the rev limiter is not a factor in this situation.

 

[Rancherlee]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

I know on another forum that a guy with a 2 tube 22' crest had a issues getting his DF140 to bite and installed under skinning which really smoothed out the water flow under the pontoon, still he only sees high 20's for speed. You should be in the 25-28mph range if your toon is a standard two tuber. Try to drop the engine as low as it will go on the transom and try that. Second, a Stainless pontoon style prop made a HUGE difference in bite over the old OMC 14x13 aluminum pusher prop I had.

 

[ShellBack101]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

I think that I am going to step up to a 13 pitch, it appears that the performance tests that I am seeing on Evinrudes site for a similar length / weight / style boat all had 13's.

http://www.evinrude.com/Content/Pdf/neutral/performanceReports/PE408.pdf


Owner of my marina, said I could try a few different ones out and decide, he suggested:

#177203 Hydrus (Evinrude)
or
#763302 (evinrude)

Thanks for the replies....

 

[rogerwa]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

The hydrus is what i am running. Since you are running a smaller and probalby lighter boat, it get you in the right range. Once thing you could do is to calculate your slippage to see how efficiently your prop is working right now. The slippage explains the difference between the theoretical speed you shold be running and the actual speed you are running.

With the numbers you provided you are running at about 36% slippage. That is assuming 5700rpm, 2:1 lu ratio, 19 mph, and 11p. Your theortical maximum with those numbers are 29.4 (I said theortical). With my setup I am getting about 25% slippage, which I am not happy about but am living with. The Hydrus prop will help with the slippage numbers due to the larger blade surface and the cupping at the edge.

 

[cc350]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

i have a 22' Oddessy 25" toons 2012 115 e-tec underskinned. Tops out around 37mph@6000 rpm with just me and 10 gallons fuel. Runs 32 mph with 2 people full tank (29 gals) cooler and gear. Running a 14x13 prop 32mph@5800 rpms

 

[Bamaman1]

Re: 22" Crest / 115 Etec - Got the RPM's but Speed is lacking......any ideas?

It's not clear what style hull you're running. If you're running a twin toon boat without strakes, you should be looking for a normal 25 mph top end. If you're running twin toons with strakes, you should be looking at 30 mph potential.

Your rpm's appear okay (or a little high), but I would expect such a boat to be running a 15 pitch prop.

You might want to start at a Prop Shop, if there's one in your area. Buy a prop from them and their expertise is free.

Or, find a good boat dealer that sells many pontoons--and that's experienced in setting them up. Not all dealers are equal.

A new prop is a good place to start.