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01-30-2013, 04:50 PM #1
Hydrostream Valero YT - Chasing +90 MPH
My fully restored and blueprinted (2012) '86 Valero YT (Mod-VP type hull) runs a soild 87ish MPH with two people and 89 MPH solo (a bit dicey solo). The motor is a healthy 235 Crossflow Johnson spinning at 6300 RPM; the prop is a 28" Chopper II that has been blueprinted and cupped; the propshaft is about 1.5" above the pad. In order to get the last few MPH out of the boat I currently have to trim it higher than I'd like.... it feels like its standing on its tail.
Goal:
A stable +90MPH boat with two aboard.
Question:
What prop will get me there?
Thoughts:
I'm thinking I need less bowlift and something that will lift the stern a bit more out of the water. Would a 30" Lightning E.T. be the ticket?
Additional but somewhat unrelated:
I'll be adding hydraulic steering and high compression heads this season.
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01-30-2013, 04:54 PM #2
I bet a 30 Cleaver or a 29SRX would put you there and some.
I've got a few props that ran really well on my V that you are welcome to come out and try.
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01-30-2013, 05:15 PM #3
Is this gps or speedo? a 30 et should get you there but the numbers do not add up if gps, it is like 1% slip, I had a ltv, similar bottom, and it liked the srx 29 and 30 et style props, good luck, Matt
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01-30-2013, 05:52 PM #4
Oldschool is right, either the tach's a few hundred low (you're actually turning 6600+) or the speedo/GPS is happy.
Not that your combo isn't capable of those speeds...it surely is. But, a few words:
-That propeller and gearcase/skeg combo is not doing you any favors. Enlarge the skeg slightly for more control, and go to a welded torque tab that's blended in. You'd better pin the carrier and stake/loctite the propshaft seals while you're at it. The OMC gearcases do not like being surfaced with large high-pitch props for very long.
-That propeller has too much positive rake, skew and blade area for that boat. You'd be much better off with a more moderate propeller like a Mazco RE or Lightning ET. With less blade area and less bow lifting rake, you'll turn more rpm and likely be a few mph faster.
-With the 235, especially if you plan to run higher compression heads, you will need 100+ octane fuel and very good oil at high mix ratio (32:1 min) to pull high rpm for extended runs. You will surely detonate pistons with standard fuel and standard oil. If you run less than 100 octane, you'll need to back the timing off from 28 to 25. Others may advise not to run 28 even with good fuel.
John
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01-30-2013, 05:58 PM #5Screaming And Flying!
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Sounds like it's running good..... If you can turn a 32 cleaver it will do 90+
83 V-King, 96 Mariner, 200 hp ff block 2.5 w/a 28p choppa
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01-30-2013, 06:08 PM #6
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01-30-2013, 06:47 PM #7
Yes I was told this prop runs like a 29, my boat is quite light and efficiet so you'd expect very low slip numbers. However as was pointed out I may have not recalled the tach after the 89 mph runs. I don't like running it past 6200 so generally let off after a few seconds. It's likely tacking closer to 6500 - which I know is not good for a cross flow. This is Part of the reason why I'm looking for more prop. Speeds are all GPS. Lower unit is from an 89GT and has a welded on torque tab and a bob's nose cone.
Would my boat really turn a 32?
The tips on longevity of the motor are noted. I always run 94 octane and good oil; I'll start mixing it a bit richer too. It should last fine with stock porting, 6200 RPM and about 115 psi of cold cranking compression. Should it not?
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01-30-2013, 07:17 PM #8
should turn a 32 no problem especially light load. I drove a friends valero yt with a 150 60* rude and a 30 et it ran 88mph first pass eye balled engine height. Im sure it would run 90s with more prop or any attempt at setting it up.
I wouldnt worry about the motor if its all stock. Just dont put 5 people in the boat and pull a tube with the 32.
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01-30-2013, 07:52 PM #9
A cleaver will really loosen up the tail and let it fly, as long as you have the setback or load balance to carry the bow.
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01-30-2013, 08:23 PM #10
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01-30-2013, 09:40 PM #11
I guess I've set up a few YTs and blown up more than a few 235s.
The 1" pitch addition is not a constant, nor a universal "always" to every equation. The engine is turning more than 6300.
It will turn a 32" as long as the load is light, and the prop does not have a lot of blade area (i.e. not a 32" V6 chopper). However, more pitch = less RPM = more load = potential detonation. Lap the flywheel/crank mating surfaces and keep RPM between 6300-6800. I'd stick with 30" or less.
recommended strong octane fuel for several reasons. One, because the engine is going to be happier with it. Two, you cannot guarantee that 93 octane pump fuel is always 93 octane pump fuel. 100LL is always 100, guaranteed.
John
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01-30-2013, 09:49 PM #12
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01-30-2013, 10:23 PM #13
Subscribed, id like to know how much set back you have? i have a 88 thats in process of recore right now kinda pumped after hearing this
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01-30-2013, 10:27 PM #14
The chopper II are big and hard to turn. They are probably a bit steeper then labeled, then plus the added cup.... In my experience bow lift is the last thing a YT needs at 90 the 30 et was a great wheel for it with similar power.
I had 3 different tachs read 3 different things on the same boat and a 2010 e-tec powerhead/harness. Chances are the older ones are off a bit.
So what do we have? A questionable tach, no idea what the actual pitch of his current wheel is and a GPS.
Try every wheel you can get your hands on. I'd keep that 28 for load and a big wheel for light passes/fun but thats coming from someone who cruises with a 34 and im looking for a 38 for the new ride
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01-31-2013, 09:18 AM #15
Wow - now there is some helpful advice!
John: I've been reading on here long enough to know to respect and listen to your advice. Unfortuantely I don't have access to anything more than 94; and I run this boat enough in the summer that race fuel would bankrupt me. When I mention high compression heads I'm speaking about the 638, 639 heads cut .020". My compression is currently 102-105 PSI in all holes, when i bolted these other heads on for fun last fall the cold cranking compression was around 115 PSI - I never tried to run the motor. My timing has been backed off to 26°. Do you think I'll be ok? When you mention pinning the carrier I assume this is so that it doesn't try to spin in the housing due to the torque applied to it by the bearings and seals? Additionally, what in your experience is the max speed i can realistically expect from this combo without turning the motor into some radical impractical thing or breaking the bank?
Baja: Wow those are some impressive numbers with a 150 on a YT! I'm leaning towards a 32 ET now; and will keep the chopper around too. The motor easily turns +6000 RPM and 85 MPH with 4 people with this prop. All the gauges are brand new and digital; I'm likely just not remembering the RPM right for those top speed passes (I should really get into the habit of using the recal function on the tach)
Phil: I have 8" of setback on a manual jackplate. It will run with 1-4 people without any changes to the engine height.
Pyro & Xstream: You're likely right that a cleaver will be the all out best prop for top speed; however at this point I think I'll go for less of a drastic change with an ET.... for now.
Pman: We might have to meet up this summer so I can take that cleaver for a rip. Thanks for the offer.