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Posted: Tue May 17, 2005 3:17 am
by dougl33
Tim, All of the guys with 87 or later boats are running 2.5:1 trannies, inch and half shafts, and 23 inch props. The difference between 15% of 23 inches and 15% of 20 inches is less than 1/2 an inch. As we can tell from all of your experimentation, prop work is not an exact science. That being said, I always wondered why Bertram switched all the gas boats. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA
Posted: Tue May 17, 2005 4:14 am
by photo finish
i dont know why propping intrigues me so much.... i am assuming they went to the larger shaft to handle the torque of the bigger prop...but wonder why they went to the bigger prop?performance,cruise speed,handling,bigger is better,prop envy,size does matter? who knows... Tim Stamm Photo Finish 1981 33' Bertram FBC
Posted: Tue May 17, 2005 4:37 am
by jav
quote:Originally posted by photo finish i dont know why propping intrigues me so much.... i am assuming they went to the larger shaft to handle the torque of the bigger prop...but wonder why they went to the bigger prop?performance,cruise speed,handling,bigger is better,prop envy,size does matter? who knows... Tim Stamm Photo Finish 1981 33' Bertram FBC If you'll pardon the input of a non-Bertram owner (hope to be someday). its generally accepted that larger props are more efficient (efficient as in converting torque to thrust, not efficeint as in slip). Doug, your right on the 15% of 23 vs 15% of 20 being very slight but, the 23" prop is already 1.5" closer to the hull (for a given strut) so when you take that 1.5" into consideration, the 15% is blown away. I've followed this whole post and it's quite interesting. Your one of the few thats posted DQX info. I have talked to Greg at Michigan several times about props and especially the DQX. I was impressed enough to order a set until I found out my size won't be available til June... otherwise I would have. I have a diesel boat that runs around 90% throttle at cruise and its a toss up when comparing DJX / DQX as theres not much data out. Please keep us posted with your results... I'm very interested.
Posted: Tue May 17, 2005 7:37 am
by photo finish
John, why would you go with a 3 blade instead of a 4 blade on a gas boat? Tim Stamm Photo Finish 1981 33' Bertram FBC
Posted: Tue May 17, 2005 8:07 am
by jav
quote:Originally posted by photo finish John, why would you go with a 3 blade instead of a 4 blade on a gas boat? Tim Stamm Photo Finish 1981 33' Bertram FBC Tim, Sorry... slip of the fingers. I would go DQX on a gas carburated boat (not DJX). I would go DJX on a diesel boat that runs 85-90% throttle at cruise due to higher efficiency of a 3 blade prop. I'll edit my post.
Posted: Wed May 18, 2005 4:21 am
by Bob S
Here are some pics of my ongoing install. Starboard will go in on Sat. Port is in and I am working on exhaust plumbing and electrical. Shafts are being delivered today.[img]
www.bertram33.com/images/uploads/E:\per ... OATS\APRES SKI 33\Engine room photos\05-05-17 RAS\starboard.jpg[/img][img]
www.bertram33.com/images/uploads/E:\per ... OATS\APRES SKI 33\Engine room photos\05-05-17 RAS\port.jpg[/img]
Posted: Wed May 18, 2005 8:24 am
by dougl33
Bob, All I can see are red x's. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA
Posted: Wed May 18, 2005 8:45 am
by photo finish
the first time i tried to put pix on i got red xs... i made the pix smaller and that helped Tim Stamm Photo Finish 1981 33' Bertram FBC
Posted: Wed May 18, 2005 9:16 am
by Bob S
Posted: Wed May 18, 2005 9:24 am
by Bob S
sorry guys. I quess I'm not as computer literate as I thought. I will try one more time[img]
www.bertram33.com/images/uploads/c:\win ... p\port.jpg[/img][img]
www.bertram33.com/images/uploads/C:\win ... rboard.jpg[/img]
Posted: Wed May 18, 2005 9:26 am
by dougl33
Nope. Not yet. Try emailing them to Dave. Maybe he can post them for you. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA
Posted: Thu May 19, 2005 3:14 am
by photo finish
Bob, i checked on my shafts and they went from 88.5" to 85"...my engines had to be moved back about 5-6"and with the shorter transmission the shafts ended up 3.5"shorter...so i am assuming your engines are pretty close to the original spot maybe 1-2" moved forward? Tim Stamm Photo Finish 1981 33' Bertram FBC
Posted: Thu May 19, 2005 5:36 am
by Bob S
Actually my motors moved back about 3-1/2" and up 1". My new set up (motor and gear) is 7" shorter than my old. Old was BW 72 and new is ZF/Hurth 63A. That accounts for the 4" extension. Sorry about not being able to upload the photos. I am not sure what I am doing wrong.
Posted: Fri May 20, 2005 9:46 am
by Bob S
Posted: Fri May 20, 2005 10:06 am
by dougl33
Nope. Still red X's. Regards, Doug L. 1986 33 Bertram FBC Queen Elizabeth Marblehead, MA
