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

13 Replies

Dr_Jay
Explorer
Jun 13, 2014
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
Explorer III
Jun 13, 2014
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
Explorer
Jun 13, 2014
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.

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Cummings ISB 5.9L Turbo Diesel 300hp

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