Uncle Vic , pls some advice on Cummins 6BTA 260

[luis]

Walter told me that you have Cummins 6BTA 260 and because I'm dealing to buy same type engines (completely recon and at a good price), he told me you have propellers 20 diameter 24 pitch is this right ? Normal 20 x 24 or with any cup? I am thinking on mounting the old gearboxes B&W 72C 1.51:1 because it seems its ok and order 2 new propellers.
Can you give me some advice on these questions? And do you think B&W 72C are good for that engine? Sorry for so many questions but here on boats normally we don't find such kind of Cummins but I like them and here is the best place to ask for help.
Thanks and best regards

[In Memory of Vicroy]

Luis - I have the 6BTA 250s which are the same as your 260s. I'm running them through ZF IRM 220a Gears at 1.5 to one. Props are three blade Nibral, no cup, 21x22.

The boat is a 1972 FBC with half tower and full enclosure, a genset, etc.....loaded down with 222 gallons of diesel, and I guess her cruising weight at about 13,000# She turns 2650 WOT and shows 27 kts.....cruise is 2400 rpm at 24 kts and 16 gallons per hour, including the quarter or so for the 6.5KW genset.

My set up is underpropped.....the boat will go from 650 rpm idle to WOT in about 6 seconds regardless of load. Many of the guys on this board have been on her when she was loaded down to the gill wityh 13 big guys and all their gear for a week and no problem, she will tote the load all day long.

Just be sure you prop her to reach at least 2650 rpm WOT with a full load aboard. My favorite set up for a B31.

UV

[In Memory Walter K]

Luis- Aren't you glad you asked? I was part of that fully loaded boat and was duly impressed! Walter

[luis]

You know my Ber31 have a "aftcabin" made by a previous owner and we use her for full hollydays, sometimes 6 persons with full gear (ladies is the worst) and diesel and water (150 lts) and generator and spares&tools and and and , meaning (last time on the travel lift - just to know - ready to leave) about 15.000 Lbs.
3 years ago we went south, about 250 miles, we made it on 3 runs, cruising at about 14/15 knots, almost no wind, we made it mainly during the night, and as always it has a delicious trip. Is like going on rails.
I have a 4 blade propeller and I was thinking on going with your advise on diameter and pitch but you have only 3 blades. Should I go 3 blades ?
Thanks UV and Walter

[In Memory of Vicroy]

Luis - try the 4 blade if you alredy have them. The rule of thumb is adding a blade is the same as adding about an inch of pitch to a three blade, if my old, fading memory serves?? Am I off on this one Faithful?

The critical factor is to be sure both engines will turn up to

UVat least 2,650 RPM at wide open throttle with a full load - if they turn less, you are overloading the engines and they will not last, regardless of what rpm you cruise.

UV

[luis]

Thanks UV I'll try it. However I still have about 6 or 7 months till go to the water. I go to finish the deal on the engines and start looking for a Twin disc or a ZF gearbox (1.5:1). And keep on rebuilding.
Thanks again