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422 acme |
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schultz227 
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Joined: August-20-2019 Location: Indiana Status: Offline Points: 49 |
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 Topic: 422 acmePosted: June-10-2020 at 10:16pm |
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1992 SNOB 351 1 23 1 tranny, put a 422 on yesterday and my rpms dropped from around 4800 to 4100. Had an acme 1868 on with the higher rpms. Just wondering if the lower rpms is ok on the engine. Boat runs smoother and quieter with the 422. I am happy with it as I don’t care about top end really. just want to know if my rpms being that much lower is correct for that prop.
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schultz227
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Joined: August-20-2019 Location: Indiana Status: Offline Points: 49 |
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Posted: June-10-2020 at 10:22pm |
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NOT High Output 351 , by the way
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3777 |
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Posted: June-10-2020 at 10:36pm |
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I have a new 422 Acme on our 95 closed bow Ski Nautique, 310 hp version, spins a touch over 5,000. Maybe it’s time for a power upgrade!
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TRBenj
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Joined: June-29-2005 Location: NWCT Status: Offline Points: 21198 |
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Posted: June-10-2020 at 11:12pm |
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If you’re not pulling a 422 4400ish then you’re either at altitude or in a poor state of tune... or your tach is lying. Get some reliable speed numbers to help us pinpoint.
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AAM196
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Joined: October-23-2012 Location: Pittsburgh, PA Status: Offline Points: 846 |
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Posted: June-15-2020 at 2:37am |
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agreed... I run my 422 om my 99SN gt40 at 2,465 ft above sea level at 4,860 rpms 46 mph...
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stepper459
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Joined: June-17-2007 Location: United States Status: Offline Points: 349 |
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Posted: June-15-2020 at 1:40pm |
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4,100 does seem a bit low. On my old boat I ran the 1868, 654, and 422 back to back just to see what the numbers would be. I saw a 200 RPM difference each time The boat wasn't a CC but it had a GT-40 and PCM 1.23:1 transmission.
1868 - 4700 RPM 654 - 4500 RPM 422 - 4300 RPM I'm curious to hear from NON-GT-40 people with a 422, what they're seeing for WOT RPM. |
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gun-driver
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Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
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Posted: June-15-2020 at 1:52pm |
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The OP has a ‘92 so non GT-40 not sure on which version HP motor he has.
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Jonny Quest
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Joined: August-20-2013 Location: Utah--via Texas Status: Offline Points: 3009 |
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Posted: June-15-2020 at 1:54pm |
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I'm at 4,400 to 6,000 feet of elevation with a GT-40 and I run the 654. My old boat had the H.O. carb engine and it also ran the 654. When I moved from Texas to Utah, I ran the 1868 at first, but the RPMs were too high at WOT. Great hole-shot, but I went down to the 654. I realize that your engine is NOT the High Output, so I would be leaning toward the 654.
I agree that 4,100 RPMs seems too low. As Tim mentioned, you should verify that RPMs are correct and that engine is properly tuned before making too many decisions. JQ |
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Current
2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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TRBenj
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Joined: June-29-2005 Location: NWCT Status: Offline Points: 21198 |
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Posted: June-15-2020 at 1:58pm |
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schultz227 wrote: