bertram31.com

1968 31' FBC

300hp cummins. full tower, genset.......

going to 1 1/2 inch shafts..

what props do i buy ?????????????? I'm guessing whatever i buy i'll end up tweeking, but where do i start? I plan on using the same struts that i had with 454 crusaders, previously 1 3/8's shafts.........

I like speed but don't want to sacrifice range and longevity of my 300's which i keep reading that I should treat like they are 250's.........so, if i had to say what was most important? i'll sacrifice top end for good economical cruise......

I have 250 Cummins w 21 x 22 4 blade nibrals 2200 rpm = 22 knots 2600 rpm = 26 knots, etc..... @ 750 rpm idle I'm doing 5 knots

jay ; nibral 3 blade michigan dyna-jet 21" dia/ 23 "pitch /full cup
no tweaking

HyTorq

I see that no one has mentioned a gear ratio. That means to me that the original ?? & the answers don't mean anything. Or are we just assuming that every one is 1:5 > 1.
Al

lobsta1 -- good point!

yes they are 1.5 to 1 ZF 220A

TD 1:54

I have the same exact setup in my 33 as do several other 33 owners. Most are running 3 blade 21X22 with a med (aka #5 cup). My cruise is 23-24 knots at 2400rpms. WOT is just over 2900rpms and speed is 28-29 knots. I'm assuming you've got cpl 0970's. Make sure you can obtain 2900rpms+ at WOT. I'd go with the Mich nibral DJX. That's Mich skewed blade prop. As smooth as their old 4 blade DQ's. Nibral is a must.

doug that is why i said full cup and 23 pitch . do to the extra weight and hull size you would have to go down a pitch size and less cup.jay has cpl 0970 and i want to make sure of the 2950rpm .

1972 B31 FBC, heavy with half tower, genset and lotta stuff. 1.53 ZF IRM 220As, 250 Cummins CPL 1247s, Michigan Dyna Jet 21 x 22 three blade nibrals with no cup. Same performance as Andre. WOT 2650. Make sure the CPL 0970s will turn 2900 WOT if you want them to last, and do run them like 250s, cruise at 2400.

UV

Q#1
Does $995 per prop for Michigan Nibral 3 blade 21 x 23 with 1.5 bore, cupped sound like a good price?

Background:
...........previously i was running 17 x 19 3 blade props on 1 3/8 shafts behind my 454's.

I am having bearings put in struts to accomodate new 1 1/2 inch shafts, hoping to use same shaft logs. will order new shafts at appropriate time.

Q#2
Is going up to 21 x 23 inch props coming thru old struts going to present any issues? do i have enough room under there without making any other changes?


Q#3
My shaft logs interior diameter appears to be 1 3/4 inches. Is that plenty of room to get 1 1/2 shafts in.

Price sounds real high to me. Try Jefferson Propeller in New Orleans, 504 340 7077, www.jeffersonpropeller.com I have bought from them and many others here have as well, always seem to be lowest prices. Seems like the last 21x22 three blade nibral Michigan I got from them was in the $500 range.

I have no trouble swinging a 21 inch prop and your struts should be okay with the new cutless bearings. I had to replace my struts due to Katrina damage and the new ones from Danny at High Tide are real beffy, but cost about 900 each...ouch...

UV

Vicroy thanks. My pricing turned out to be in line with them. I guess the only decision I have is to pull the trigger or chicken out and buy brass!!!

If the props are the DJX Nibral then that's a great price.

Fishlook, please see the PM I sent. Thanks.

I was told to have 1/2" clearance ,, 1/4 each side theoretically, might get a bit tight with only 1/8 " on each side of shaft,strut and motor alignment could already be off but not a problem with current setup

All metals are high