Who has experience with twin screw impellers?

[FSH 210 Sport]

Thanks!

Your density altitude was 2878’. I had to make some assumptions since I didn’t know the other parameters of altimeter and dew point. I don’t have a good feel for a SC engine and how it would be affected by that 2900’ elevation but I’m sure there is some affect, maybe 5% or 25 hp loss.



I don’t know the conditions when you tested the oem impellers.

I’m assuming you already have the 12/18’s, if not you could have Dave at leading edge take some pitch out of the ones you have, much less $$$ to do it that way.

If it was me, I’d try the 12/18’s or repitched first and see what rpms and performance you get out of those. I’m sure you will gain rpms, it will be interesting to see if the 12/18’s get you back up to the oem impeller rpms range / speed or closer to the rated max rpm of 8000 and should get you back up to the oem top speed?

If I remember correctly, the tuner will only give about 5 hp at the stock rev limit of 8000 rpm, raising the rev limit to 8500 is where the 25 hp gain would be seen, but that requires a lower pitch impeller to get that many rpm.

 

[jacoviii]

Well I just pulled the L13 cones off and went to stock. It revs much quicker. Now port is 7600 and Starboard is 7500 much better acceleration (punchy). Top speed 52-53mph. Before with the L13 I felt like the power and take off was very linear... I will still try the 12/18. With each cone. But we are heading to lake of the ozarks next week to watch the races. I know the impeller tuners have their value. But I'm looking to do as much in house as possible.

 

[F.M.]

Looking forward to the results of the 12/18 vs the 12/20. I hate that you had to pull the L13 cones to raise the RPMs. I fell like the L13s provided a noticeable difference in holehsot and acceleration on my '17 242X, but it seems like on the new 160mm pump they don't provide as good of results.

 

[jacoviii]

Looking forward to the results of the 12/18 vs the 12/20. I hate that you had to pull the L13 cones to raise the RPMs. I fell like the L13s provided a noticeable difference in holehsot and acceleration on my '17 242X, but it seems like on the new 160mm pump they don't provide as good of results.

They do in the wave runners and in a stock 160mm impeller boat. But I belive the L13 is a bit much with the twin prop. And factory nozzle size. Don't be put off with my top speeds 54mph was my best brand new. Maybe 55mph ish once.

 

[F.M.]

I would’ve thought your top speed would have been much closer to mine stock since we’re only at about 300’ of elevation difference. My top speed, unmodified, 2 people, half tank of fuel, roughly 75 degree temp, was 58mph. Fully loaded, full fuel, 4-5 people, 56 mph. Now in 90-95 degree temps I’m only getting 54mph.

 

[F.M.]

@jacoviii

How were the races and Late of the Ozarks?

Any luck on trying out the 12/18?

 

[jacoviii]

Day one we mostly got rained out. 50+mph winds. Day two was good. We seen a lot of nice boats. 12/18 are going on this weekend and I have a Maptuner coming too.

 

[F.M.]

Weather sucks sometimes. A least looking at boats is fun.

Really hoping you have good results. I’d like to get over 60 with just my current mods and impellers without spending the money for the tuner. Don’t think the wife will go for that this season.

 

[jacoviii]

Ok well it was 15-20mph cross winds at the lake and the water was busy. But what I was able to tell with the 12/18 was port is 7700 and Starboard is 7600 a little bit better acceleration ( still punchy). Top speed 51 but the gain in speed from 47 to 51mph is a bit slow. I'm still running stock cones on this test. I'm going to keep it set up this way and run it again, hoping the wind calms down tomorrow.

 

[F.M.]

51 is quick with 15-20mph cross winds. Boating at all with 20mph winds is pretty brave.

 

[jacoviii]

Ok yesterday was still a bit windy but port was 7800 and Starboard 7700 with a top speed of 53mph. I felt a bit of cavitation. So I will do L13 cones this weekend.

 

[FSH 210 Sport]

Ok yesterday was still a bit windy but port was 7800 and Starboard 7700 with a top speed of 53mph. I felt a bit of cavitation. So I will do L13 cones this weekend.

When / where did you experience the cavitation?

 

[F.M.]

Any luck with the L13s and the 12/18 impellers?

 

[FSH 210 Sport]

Ok yesterday was still a bit windy but port was 7800 and Starboard 7700 with a top speed of 53mph. I felt a bit of cavitation. So I will do L13 cones this weekend.

Were you able to get out and test with the L13 cones?
What were the results with the map tuner?

 

[jacoviii]

Yes I did a bit more testing. The L13 no shims helped a bit but nothing drastic. I'm out of season now and will be waiting till next season for the tunes. The 12/20s with no L13 cone was all around good. I'm going to start next season with the 12/18s & L13 but also try the 12/20s again. I'm also going to get the impeller degree gauge to better document what I'm working with.

 

[FSH 210 Sport]

Yes I did a bit more testing. The L13 no shims helped a bit but nothing drastic. I'm out of season now and will be waiting till next season for the tunes. The 12/20s with no L13 cone was all around good. I'm going to start next season with the 12/18s & L13 but also try the 12/20s again. I'm also going to get the impeller degree gauge to better document what I'm working with.

Thanks for the update!