Cummings ISB 5.9L Turbo Diesel 300hp

[Octanefam]

I'm new to the diesel engines so how many different Cummins engines do they normally use for RV's? Someone was telling me that the ISB 5.9 is small for a diesel pusher?? So please done rip on me if this is not accurate.

Oh BTW we are looking at 1999 - 2002 Diesel pushers.

THanks

[bamaboy473]

explorenorth wrote:
My thought is that if I can get in under 120,000 km (80,000 miles) for under $55k, it will work out well. Any thoughts on that will be appreciated.

Having just bought a 2006 36' DP with less than 10,000 miles, I can assure you that you will be able to find one of 2002 32' DP, and those miles for MUCH less money than you're budgeting.

[bamaboy473]

Dog Trainer wrote:
Look at the weight and length and if you are in the 100 hp per 1000 lb category the 5.9 will be adequate. We have put many thousands of miles on our B5.9 12 Valve and as others have stated she is not a speed demon up the hills. On the flat she really likes to run and I can get an honest 11 MPG with my Allison 6 speed but then again I am just at 22,000 lbs.

We've heard that 1HP/1000 pounds is a decent rule of thumb that manufacturers use to mate engines to their DPs. Ours weighs 28,000 pounds, has the 300HP engine, gets between 9-9.5 going 62-65.

[Dog_Trainer]

Look at the weight and length and if you are in the 100 hp per 1000 lb category the 5.9 will be adequate. We have put many thousands of miles on our B5.9 12 Valve and as others have stated she is not a speed demon up the hills. On the flat she really likes to run and I can get an honest 11 MPG with my Allison 6 speed but then again I am just at 22,000 lbs.

[Canadian_Rainbi]

explorenorth wrote:
I'm looking at buying a 2002-2005 Winnebago/Itasca 32-footer with the 300hp (several possibilities at the moment). It will be towing a Chevy Tracker, with lots of mountain routes - the 32-foot maximum is to get into some odd places in the Yukon and NWT in particular. I've already ruled out the 275hp models as not having the power I'll need (ie the Winnebago 32T), but the 300hp will do the job, I think. I spent the last 35 years of my working life driving diesels, 350 Cummins and old Detroits, so have a decent knowledge of the pros and cons. The big question is the $/mileage one - what sort of mileage can I buy and still expect to put lots more on before the big bills for maintenance start arriving? My thought is that if I can get in under 120,000 km (80,000 miles) for under $55k, it will work out well. Any thoughts on that will be appreciated.

Our 32' Itasca Horizon, Cummins 5.9, Allison trans. . . 140,000 kilometers since 2009, Vancouver Island to Mexico every year, once the long way around via Alaska and the east coast--a 10 month trip.

No engine or trans problems except: Blew the serpentine belt on a Mexican toll road--7 hours to get going again: NO SPARE BELT :S I have one now :B We now have a very slight rear seal leak that we will have taken care of this summer.

We towed a Chevy Tracker 2 door for a couple of years with this rig(including the Alaska Trip) and then a 4 door Jeep Wrangler convertible for the next three. It handled both quite well. Just don't be in huge hurry. It handled better than the older (97) 30' gas Class A we had before.

The cruise control and exhaust brake make going down hills a piece of cake. As I said though, don't try to rush. According to our Silverleaf PC we have averaged 8.3 MPG over the last 20,000 or so miles. We tend to keep the speed down to about 60 or a bit over (lets 6th gear kick in) unless traffic dictates otherwise (busy traffic in 65 or 70 zones.) We NEVER drive it at 70.

PS: Had the slide motor fail in Whitehorse. Waited almost two weeks for parts then drove about 5 K down the Alaska Highway with both slides out to the shop!

[explorenorth]

I'm looking at buying a 2002-2005 Winnebago/Itasca 32-footer with the 300hp (several possibilities at the moment). It will be towing a Chevy Tracker, with lots of mountain routes - the 32-foot maximum is to get into some odd places in the Yukon and NWT in particular. I've already ruled out the 275hp models as not having the power I'll need (ie the Winnebago 32T), but the 300hp will do the job, I think. I spent the last 35 years of my working life driving diesels, 350 Cummins and old Detroits, so have a decent knowledge of the pros and cons. The big question is the $/mileage one - what sort of mileage can I buy and still expect to put lots more on before the big bills for maintenance start arriving? My thought is that if I can get in under 120,000 km (80,000 miles) for under $55k, it will work out well. Any thoughts on that will be appreciated.

[klm]

I am a fulltimer, my '02 Newmar Kountry Star has the ISB 5.9 300hp. I am not engine tech knowledgeable, so I can't give you any specs, etc. I can tell you I have traveled up and down many, many mountain passes - not at jack rabbit speed, but that's A OK with me. I have 98k miles on that engine, and plan on putting on lots more.

I did have a fuel pump failure, if I remember right (it's been several yrs ago), the particular pump was known for problems - a Bosch 44 - . That has been my only engine issue.

The rear radiator needs to be cleaned on a regular basis, otherwise you might start running hot climbing.

I have gotten 10mpg, but generally more like 9 - 9.5. I tow a Honda Fit, about 2500 lbs.

[liveneasy]

As a full-timer... my Holiday Rambler weights in at just under 25,000 pounds and I pull an '03 Tracker that weighs in around 3,500 pounds. My coach has the 6BT 5.9, that's the manual 12 valve version (with the Banks Turbo kit) instead of the ISB 24 valve engine... and I've driven it through all 48 states, Canada and down through Mexico to Guatemala a couple of times. While I won't be the first one up a long grade, I can keep up with the best of em on the down grade... so I consider it a wash, besides I'm retired and not in a hurry. The engine is very reliable, will cruise at 62 all day with power to spare and starts darn near instantly every time. I've never driven another DP so I don't know what if anything I'm missing with the smaller engine. Bottom line, I'm happy with it's performance and it's consistent 10 MPG.

[Fishinghat]

The ISB Cummins is a good engine and will get you anywhere you want to go. It is the smallest of those used in motorhomes, with the ISC 8.3 preferred for larger coaches. The ISL 8.9 is a "improved" version of the 8.3 with even more torque and power. Finally, the ISM and ISX are rated up in the 500+ HP ratings for even more power. Now, if the ISB was "enough", none of the manufacturers would install the larger engines.

Going south over the Siskiyous in Southern Oregon and Northern California can be taxing in an ISB couch, but you'll eventually get there. Ditto with Snoqualmie. Otherwise, trips to the coast or north to Canada won't be a problem. You won't be passing anyone, but you won't be holding up traffic either.

Depending on weight and how you drive, you'll get probably something between 8 and 9 mpg, regardless of which engine you get. Fuel economy is a TINY cost of RV ownership. Depreciation is the big one.

[Gjac]

My friend had this eng in a 34 ft Bounder DP. I liked the MH because of the size. He though it would get 10 mpg but never did better than 9. The performance was a lot worst than a gas MH of the same length. He only had it for a year and had a lot of other problems with the MH not the eng. I would have bought it from him but did not like the performance. If you never plan to take it out west it may be ok for you.

[JimM68]

In that age range, the majority of smaller DP's will have the 5.9.
Good engine. Not a speed demon or torque monster, but reliable and many who own them claim MPG's that seem unheard of for a heavy DP motorhome.

[Dr_Jay]

Great diesel. Had it on my Dodge Ram 3500 pick up. I used this pick up to haul my 12K pound fifth wheel up and down hills and mountains with no problems and enough power to spare. Now my truck loaded w/o the fifth wheel weighed about 7500 lbs add that to my 12K fiver and you have a total weight of about 19.5K pounds.
Good luck and happy trails.

[Ivylog]

The 5.9 is a great LITTLE engine and does well if the MH is not very heavy. The next size up is the newer ISB 6.7L, then the Cat 3126/C7 at 7.2L, then the ISC 8.3L, and then the ISL 8.9L in the 400 HP and less. A ISC 300 HP will have 1000 ft lbs of torque while a ISB 300 HP will have 660 a BIG difference for pulling even small hills.

[Gale_Hawkins]

The 5.9L is a good engine I read until you drive on with more power. 🙂

If you are driving in the rocky mountains pulling a 20,000 pound trailer you need more power than driving from Houston to Gulf Shores MS for example.

Some can do a 30 day trip and drive 8,000 miles and others may do a 30 day trip and not drive the MH 80 miles (common here in the KY Lake region) so what is OK engine wise will be determined by usage.