Shorties
 

I know this topic has been beaten to death so I will be very specific in my question. I have a 2000 38 Lightning with 525sc's. I am installing a set of -2" IMCO's. My current prop is a 26 Q-iv hydramotive spinning in. My question is for those of you who have or had a 38 Fountain with small steps and have added the shorties. What props did you end up with for best overall performance and best top speed? Turning them in or out? Cut diffuser ring? Trying to get close to what I need before splashing and testing the boat.

I turned a 30 Bravo before shorties, and after tried the 30 Bravo, and 30 Maximus (cut down diameter) after shorties. I picked up ZERO. Boat runs flatter and rides better, but don't expect any gains based on my experience. I prefer the 30 Maximus, it's a bit over propped for me, spinning only 5000 to the wood, but it has a mean cruise.

What ratio are your drives? Are they regular Bravo or XR, XZ..etc. Reason I'm asking is your spinning a 26 now, so you might be a 1.36 . Back in the 90's and early 2000's they put a lot of 1.36 uppers in regular bravos for strength. I would run what you have (26) and see if you can borrow a set of 28 Bravo 1's and spin them in.

To my knowledge they are 1:50 standard Bravo's. Not the original set that come on the boat. I spin them in already and will start with what I have. Thanks.

I agree that they are prob 1.36, what are you seeing for top speed and at what rpm now? Seems like a lot of power for 26 pitch. My boat with 575s came with 32 that would hit the rev limit on cool days with 1.50 drives.

So you don't no for sure what the upper ratio is, but you got some -2 shorties???? How did you no what ratio gears to get in the lowers??? You may have changes you overall ratio from whatever you had. So, with that being said... you need a baseline (rpm & speed) of your original setup, then put on the -2 shorties and see what RPM & speed you get, and go from there.

Call bblades and test his props. Its realativly inexpensive. Thats where i got mine. 5 bl hydros is probably what you need. 2 inches does nothing unless you are close to the surface with the propshafts

I liked back on another thread, you stated you got 81.5 mph out of your boat at 5200. You have 1.36 drives. 1.5 doesn't add up in a prop calculator

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if they are bravos, would the lower gears change the ratio, i thought xrs were changed in the lower

Ok went testing today. I was gathering info on what I have on the boat. This is the assumption of 1:50 gears and I could be wrong. Having said that. 26 pitch hydramotive quad 4, 5400rpm, 1:50 gears (assume) 80.5 gps 9% slip on herrings calculator.

Ok. How do I tell what gear ratio I have??? SN? Stamped on gears??

With those props and that hull, no way are you at 9% slip. If that would be the case, someone did a hell of a job building & setting up that boat. As for gears.. All XR's have 16/19 gears in the upper, there is several different combinations that can be done with upper & lower gear sets on bravos... If you don't have an XR upper you could have like 4 different ratio gears in just the upper, then there are 3 different ratio's in the lowers for sporty's XR's etc....... You have to count teeth to find out what ya got.

and 18 percent slip to do those numbers at 1.36, man I don't know. 9 percent is hard to achieve on a v bottom, and 18 is too high for a stepped fountain. 13-14 is about average.

Like bawana said, 9 percent would be sick prop, lower and bottom work....but it is possible.

You can count gears, or you can pull the drive off and rotate 10 times and do the math on input vs output

On my 38 Fever I went from a set of XR sportmasters to a set of -2 imco's and it picked up about 5mph. I did however have to add a set of pressure relief valves because the pick up for the imcos are so much larger. The boat ran best and fastest with hydro P5-X's.

you don't have 1.5's. I run about 11- 12 slip with Herrings. Same hull, everything bluprinted. And that's a 5 blade. You having a 4 blade is gonna be higher than 12. Plus you are probably real deep in the water creating drag.. I'm thinking you are in need of better set up and props. ;) You should be around 15 -17 slip with your set up. so 18 makes sense