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| outdrive question bravo 1 https://www.smwebhead.com/phpBB3/viewtopic.php?f=13&t=4573 |
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| Author: | blairjbyrd [ Tue Sep 15, 2009 7:16 pm ] |
| Post subject: | outdrive question bravo 1 |
I have a 89 241 lib with a 454 and a bravo 1 outdrive. My gps says 43mph and my tach is at 4800 or around there. I have a 21 pitch prop. How can I get a higher top speed but not lose the preformance off the line. It planes pretty quickly. Thanks in advance. Byrd |
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| Author: | ht32bsx115 [ Tue Sep 15, 2009 11:27 pm ] |
| Post subject: | Re: outdrive question bravo 1 |
Oh no....not another Liberator!! You left out a rather important detail. Drive ratio. I'll assume that you have a 1.5:1 drive because that's probably what I'd put on that Lib......(mine is 1.81:1) Away with a 1.5:1 drive, Using the Prop slip calculator, http://www.go-fast.com/Prop_Slip_Calculator.htm : At 4800, you should be going about 55 mph with 15% slip which would probably be about right for your boat if the engine is running correctly.... But something is very wrong if the RPM is correct and the drive ratio is REALLY 1.5.......that makes your slip at 33% indicating that you're either REALLY heavy (waterlogged?) or the bottom is literally COVERED with marine growth. So, you need to do a couple of things to proceed. 1. You need to verify your tach. (make sure it's accurate) maybe even get another one and see if it's the same .......... My tach recently has started registering low at high RPM for some reason..... 2. You've verified your speed. 3. determine your drive ratio. (is it really 1.5?) 4. Try a different prop. (is yours a 4 blade...is it SS?)......Try a 3 blade 21p SS prop (4 blade props are usually a little slower than a 3 blade although not THAT slow) If the RPM is correct. (and the GPS is correct.....I haven't ever seen a GPS be wrong) then something is "holding" the boat back. (waterlogged, dirty hull, etc.......you dragging an anchor?) If the RPM is NOT correct, then the tach is screwy....AND you have engine problems. rebuild the carb, correct the timing, check the compression etc. For that boat a 21p prop should be close to "right". When I had the 460 and King Kobra in mine (1.41:1 drive, 20p prop) I ran 60 mph at 5000 RPM. I was a little slow out of the hole though.........even when it was brand new ..... but not now...... POST PICTURES!! It's always neet to see another Liberator!! Cheers, Rick |
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| Author: | blairjbyrd [ Wed Sep 16, 2009 10:22 am ] |
| Post subject: | Re: outdrive question bravo 1 |
Could the prop hub be bad. I just bought the boat. I had to put a new engine in it. It has been sitting for 2 years. The bottom of the boat is clean, there is no anchor dragging. I will find out what the ratio is for sure and get some pics for you. Thanks |
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| Author: | ht32bsx115 [ Wed Sep 16, 2009 12:47 pm ] |
| Post subject: | Re: outdrive question bravo 1 |
blairjbyrd wrote: Could the prop hub be bad. I just bought the boat. I had to put a new engine in it. It has been sitting for 2 years. The bottom of the boat is clean, there is no anchor dragging. I will find out what the ratio is for sure and get some pics for you. Thanks It's pretty unlikely that the hub is bad. When they slip it's usually an "all or nothing" slip. And it doesn't last for long until it just completely destroys the rubber "snubber" then you don't go anywhere. I would still try a different prop though. You really need to know your drive ratio. It should be on the (port) side of the drive on the serial number sticker (unless someone changed it) If you cannot find one, you can pull the plugs and turn the engine exactly 3 revs with a wrench and if you're a 1.5, the prop should turn exactly 2. A boat that size should probably get a 1.5:1 drive. Four Winns did put the Alpha drives behind the 454 for a couple years and I think they used a 1.36:1 ratio. Mercruiser found that the 454 was too much for an Alpha and came out with the Bravo around 89. (maybe yours came with the Bravo?) There's a lot of Liberators out there with 454's and Alphas.....maybe someone can jump in here and report their ratio/prop-pitch & performance. When my Brother bought my boat new he drove both of them ( 330hp Merc 454& 340hp OMC 460) and thought that the 211 with the 460 was a little faster (he was all about speed!)......with only a 10hp difference. I bet there was no difference.... The only way you're going to get more top speed is probably to crank up the RPM if you don't have a rev limiter. If you go to a higher pitch, you probably won't go much faster and your hole-shot will suffer. Also, you need to trim the drive while you're underway. You can improve the hole shot by running the drive all the way -IN until you 're up on a slow plane. Then trim the drive OUT in small bursts while you watch the speed. You can tell when you get trimmed out too far because you'll "porpoise" more in light chop.... but trimmed with the bow down too far on a fast plane will REALLY slow you down. You have to experiment... I would also run the boat and trailer over a public scale so you can see where the weight is just to rule out weight....... |
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| Author: | blairjbyrd [ Wed Sep 16, 2009 2:59 pm ] |
| Post subject: | Re: outdrive question bravo 1 |
I will check when I get a chance to go to the marina. Thanks for your help |
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