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Right prop for 98 SN 196 |
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Chicoman88 
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Joined: May-10-2018 Location: Idaho Status: Offline Points: 8 |
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 Topic: Right prop for 98 SN 196Posted: July-02-2019 at 8:19pm |
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I have a 1998 Ski Nautique 196 (5.8 GT-40) that I run at about 4500-5,000 ft elevation. What is the best prop? I bought the boat used and it had the stock Oj. I’m running an Acme 654 right now to see how it goes. Feels smooth so far, tops out at about 44 mph and 4500 rpm. Sound right?
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TRBenj
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Joined: June-29-2005 Location: NWCT Status: Offline Points: 21198 |
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Posted: July-02-2019 at 8:33pm |
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That’s not too bad, considering. 45-46 is pretty typical near sea level. 654 is a step down in pitch from stock (13x16/422) but holding you to 4500 means it’s still a tad larger than ideal.
1868 would have a little more punch out of the hole but isn’t likely to speed it up on too much (or any). 1458 might get you close to 5k and return pretty decent all around performance. 4800-5000 up top is usually optimal. |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3778 |
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Posted: July-02-2019 at 8:33pm |
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At your elevation I am not sure you can do better.
Our resident Prop guru will weigh in. TRBenj has a lot of prop experience. I use the Acme 422 at less than 2,000 ft elevation and it spins 4,900 RPM at 48-49 mph. I bet if I was at 5,000 ft it would be 3-5 MPH slower. |
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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: July-03-2019 at 11:12am |
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Different boat (heavier) but same engine and transmission: in my old Supra I tried a variety of different props because I had easy access to them.
Acme 1868 ran 4700 RPM @ WOT / 41mph Acme 654 ran about 4500 RPM / ~43mph Acme 422 ran only 4300 RPM / ~40mph The speeds aren't the most accurate but the RPM range is clear. Each step "up" (in pitch) brought the RPM down about 200 RPM at full throttle. I wanted to stay below 4,800 RPM at all times, but not load the engine too much with a fully-loaded boat. So I ran the 1868. In that heavy boat I could have gone another step "down" in pitch but never worrying about over-revving is nice, where I used to let lots of other people drive the boat, with or without me in it. |
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3778 |
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Posted: July-03-2019 at 2:02pm |
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My brother owned a Supra tournament boat, TS6M? It was carbed with the 351W.
His turned the 13x13 3 blade. He was always griping that his engine did not run right. I tuned on that thing for him, worked over the distributor and carb, checked compression and it ran as perfect as I could get it and struggled to turn that prop 4,000 - 4,100. I finally gave up and decided his boat was just heavy or had a bad hull design. It drove great, looked good and rode good but could not run with the rest of our group. We could cruise to our beach at 35-40 MPH without opening our four barrel carbs while he had to run wide open and suck up fuel. He never stepped up and bought a new prop. I know he could have picked up his RPM but not sure if it would have helped his MPH. |
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Chicoman88
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Joined: May-10-2018 Location: Idaho Status: Offline Points: 8 |
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Posted: July-03-2019 at 3:44pm |
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Which do you think is the better bet between the 1868 and 1458. Looks Iike I still need a little higher rpm’s yet over the 654.
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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: July-03-2019 at 4:00pm |
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Between the 1868 and 1458 I'm not sure there'd be a big difference, with the larger diameter 1458 you have less pitch, which will offset the size difference to a degree. Cup is different, too. Hard to say other than both are likely to bring the RPM up a little from the 654.
On the Supra, my father in law now has a 1989 TS6M ("tournament skier 6 meter") but I'm the only one who uses it to ski. It pulls fine and has a pretty flat wake. As for top speed and RPM, I really don't know. It has an ACME 422. Fun to drive but too easy to dive the bow. Mine was 21' and still easy to dive that bow haha. |
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Chicoman88
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Posted: July-03-2019 at 4:23pm |
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@Trbenj
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tryathlete
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Joined: April-19-2013 Location: Lake Villa, IL Status: Offline Points: 1799 |
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Posted: July-03-2019 at 9:41pm |
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I thought Supra’s were LH props. Isn’t a 422 a righty?
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KENO
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Joined: June-06-2004 Location: United States Status: Offline Points: 11191 |
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Posted: July-03-2019 at 10:46pm |
Supra's were kinda bisexual when it came to props. They went both ways  The started out LH then the ones with 1.23 to 1 transmissions used RH props, then when they went to Indmar engines they went back to LH |
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TRBenj
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Joined: June-29-2005 Location: NWCT Status: Offline Points: 21198 |
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Posted: July-04-2019 at 2:41am |
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How do you use the boat?
I might be inclined to go 1458 for barefoot but 1868 for dedicated slalom. |
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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: July-04-2019 at 2:47am |
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I run an ACME 654 as Tim mentions above. I'm in Salt Lake City and typically run between 4,400 and 6,000 feet of elevation. While my Ford 351W isn't a GT40, it is a strong runner and the 654 seems to be the right combination of engine and altitude. The 654 is 12.50" x 15.00" with a 0.105 cup. I did try an ACME 1868 at first, but it was a bit too high revs. The 1868 is 2.50" x 14.25" with a 0.75 cup. The standard sea-level prop would most likely be an ACME 422 12.50" x 15.50" with a 0.105 cup.
JQ |
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2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
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tryathlete wrote: