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

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.

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.

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.

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.

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.

Cummings ISB 5.9L Turbo Diesel 300hp | Good Sam Community

Dog_Trainer
Explorer
Jun 14, 2014
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.
bamaboy473
Explorer
Jun 14, 2014
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.
bamaboy473
Explorer
Jun 14, 2014
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.

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Cummings ISB 5.9L Turbo Diesel 300hp

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