bertram31.com

Okay guys....things are getting more serious by the day for repower and I want to explore all my setup options. After much debate, I'm sticking with Yanmar or remanufactured Cummins. The following ideal set-up for Yanmar was posted by Capt. Pat in another post, to wit:

315 Yanmar
Trans Gear Ratio - 2:1
Shaft - Aquamet 1.5"
Props - 20 x 24 (4) blades
20 x 23 (4) blades

As I know nothing about Cummins, can anyone show me to the right direction. I fish and cruise 50/50 of the time. Not looking for extreme speeds.

Counsellor - the 270 Cummins 6BTA is a very fine engine and will give you a honest 24 knot cruise. The WOT rpm is 2600 so a 1.5 gear is what is used vs. the 2:1 on the higher rpm Yannies. Most of us with the 250-270 6BTA Cummins run 21x22 or 21x23 three or four blades as the Cummins has more torque at lower rpm than the Yannies and will turn a bigger prop. Use 1.5" Aqumamet AQ 22 shafts. I have ZF IRM 220A gears, 1.53 to one, and they have been nearly flawless over thousands of hours. The Twin Disc is a good gear also.

The higher hp 6BTAs use a raw water cooled aftercooler vs. a fresh water cooled one for the 250-270s and the raw water cooled ones require regular maintaince (disassembly and cleaning) vs. zero for the fresh water cooled ones.

A lot of people have gone with the 300 hp BTAs (CPL 0970) and there are some issues if they are run hard or overpropped. The 330 and higher hp 6BTAs make the B31 a rocket ship and are good engines.

I have the 6BTA 250s and if they ever crap out (they were built in November, 1989, so may never) I'd go back with the 270s, the same engine with a different rating. The Cummins remans are new engines with 'reman' on them to dodge the EPA.

You won't regret converting to diesels as it makes a totally different boat in a lot of ways.

UV

Huesso

We put in the 270 Cummins remans. I run light, no tower, no hard top. I get 30.5 knots on the top end. Recommended cruise is 2000 but the dealer tells me I can run it 2400 all day.

I am running 20x23 4 blade with a slight cup. I hit the top at around 2650 RPS. We were at 2700 initially but added slightly more cup to tweek it down a little and picked up a hair more speed.

We are really happy. Only issue is I have to out the creek on one engine. Two engines in gear at idle is a little too fast. One engine is no problem with Capt. Pats rudders.

The 31 with diesels and Capt. Pat's rudders turns the thing into a Porsche.

I was going to go Yanmar but a $10,000 difference made me think about 2 seconds about it. I also thought about going up one to the 315 Cummins but the dealer talked me out of it. Would have cost me about 6,000 more plus since the turbo is sea water cooled it would mean more maintence. The 270 is freshwater cooled. The other part was like the dealer said, hey its a 30 foot boat, how many times are you going to able to run that fast.

He was right, so we put in the 270's.

Good luck and if you need more information on the 270 remans let me know.

tony you have the right idea; ADD cup not pitch to bring rpm down .also increases effiency . -----push the most water you can with the prop don`t spin the hell out of high pitch prop and let half the agitated water do absolutely nothing toward propelling that boat forward like reving the hell out of a car in the mud with balled tires!!!!props are a science no two boats are the same .if you go with 315 hp cummins they put out 681 pounds of torque at 2200 rpm almost two hundred lbs more then yanmar all you have to do is know how to harness it.and create effient fuel economy with the use of torque and prop design!!

Ive got the 330 hp remans.. Real pleased with them. With a tower & 3 baittanks/ full fuel & people,heavier than most.. ..29knots.keeps going faster everytime I check.. 900 hrs so far.
Oh I spent the $10,000 (yanny)on a rotator cuff ..
Wayne

wayne that was one of the most painful injury i ever had .the boat barrel rolled and i think my shoulder hit the wheel or side of boat . tears in my eyes as the emt cut the one piece racing outfit out from me.

last three weeks playing run and gun with the bass . i have been going 34 knots out there i wish i had 370hp in a behia-mar! last 3 years bass moving east to west stop offshore along fire island beaches feeding on sandworms . bite is over at 8:30am or when boat traffic arrives , sometimes you back the boat to 20' from beach in 8' of water because the bass chase the bait right up on the beach . very dangerous situation with the surf breaking under the boat . fourtunately north/northwest winds calm the waves in the surf.normally they past in november in 60' of water and you jig ------never say never

Anybody want to chime in on the 1 1/2" shafts vs. keeping the 1 3/8" shafts?

I understand using the largers shafts for the cummins repower, but how about the Yanmar?

I'm repowering with 250hp Steyr's and plan on keeping my 1 3/8" shafts and I was using info off of Yanmar repowers to be comparable.

Don't want to hijack Hueso.... just looking for all points of veiw.

Ray

Its good info I would think for Hueso!

I re-powered with 240 Yanmars. I kept the 1 3/8" size but put in new aquamet 22 shafts. I didn't know the age or history of the old ones. I consider them to be wear items after a certain point.

If I had put in the 315's, I would have upsized to the 1.5" shafts.

Dug

I have 1 3/8" shafts on my Cummins 210's turning 20 X 20 cupped props.

I have 1 3/8 aquamet22 with 250 cummins-so far so good. New shaft because the length was different and I didn't know the type of shaft or age (37 years i bet).

Ray,
I don't know how old your boat is, what trannies are you going to use?, but I would pull your shafts your going to change out the cutless bearings and packing glands anyway)have the shafts checked for true and magnafluxed for cracks, by a good prop company.

I have talked to Bruce about this a couple of times, I was thinking of repowering my 31 with 256 hp Steyrs. Mine has 1-1/8" Aquamet 22 with intermediate strut bearings and 1:5:1 Hurth 63A 8 degree down angle gears. Right now I run Mercruiser 7.4L Throttle bodied fuel injected 310 hp FWC 1997 engines with 5" exhaust system, no back pressure and 18x18 3 blade nibral props no cup. Boat runs 41.8 MPH@ WOT @4300, 29MPH@3000 Cruise,and can troll on one engine at 700 RPM at 3.5 MPH.
My struts are low profile angle, only 9-1/2" from the hull bottom to the bottom of the strut barrel with intermediate struts, he largest prop I can turn is 18".
I think anything bigger than 1-3/8" shafts on 256 hp Steyrs would be overkill. Gear ratio, prop set-up and shaft angle are the main things on a 31 Bertram. Extra Dry and Sandy Bird both run 240hp Yannies with 1-3/8" shafts and 1;5;1 gears and turn 28 knots at WOT from my ld data base. ust my 2 cents worth

With the 270 Cummins we had to up the shaft size to 1 1/2 aquamet 22. Bored out the old struts and put in a thin wall cutlass bearing.

hueso with 315hp cummins reman. you would use 1.5" aquanet 22 shaft with 21" dia. 23" pitch and full cup and if you have a trusted prop garu a 4to 5 degree rake . eliminate the " flaps" on the stern and you will have a package that will last a lifetime and then some.

Good input coming in on the shaft size everyone's using... thanks.

Pete,
I'm going to be using the 63a's also, but with a 2:1 ratio. I've got one gear being shipped right now and I'm still in the market for one more.

I replaced one of my shafts when I first rebuilt the boat around 1986 and I don't know the material... was aquamet available back then?

My B31 repower/rebuild won't start till at least next summer... way too many projects going on now... but I picked up the Steyrs for such a great deal IMO ,so I don't mind warehousing them for a bit.

I have a B28 w/240hp Volvos (1.25" shafts) that I would at least like to hang a for sale sign on before I start on the B31 again. But then again.... who ever said you can have too many boats.. ;->>

Ray

Ray,
My shafts are 1-1/4" not the 1-1/8" I posted earlier, Aquamet has been around for quite a while, yours are probably are Aquamet, too many pain killers since knee operation. On prop sizing make sure you have atleast 1-1/2" of clearance between blade tips and the hull bottom, you don't need to have cavation burns in you hull. The 63 A Hurth trannies are pretty good, I did have a noise problem at low speeds with my gassers, both trannies sounded like a coffee can full of bolts, changed out the spark plugs and noise went away. The original spark plugs were AC's from factory, an old timer at the marina told me to change out the plugs, it worked.

Pete what fuel burn numbers are you seeing in gph total and mpg? Thanks.

I'd like to know as well your numbers Pete, thanks. The TBI, is that an aftmkt system? And maybe some numbers on cruise say, at 18-20mph?