Cummins diesel

[Dutchv]

I’m in the market for a new motorhome, I’m looking at a couple with the 300 horse Cummings, I was wondering is this the 5.9 L ISB
Any feedback would be great thanks

[ray999]

Can you give an idea of the make and size of the coaches? Not sure if 300 has enough power.

[Dutchv]

What size is the 300 hp Cummins?

[Tonkexpress1]

Not sure about your question, but be careful with the length ie. 40’,38’ or 36’. With only 300 HP that is not a big enough engine to handle long inclines or mountainous traveling. And, if you have a toad — more weight to pull too. Flat traveling would probably be just ok— nothing special. Personally, I would not even consider it for a class A rig. Good luck in finding what you want because it’s fun out on the road with new adventures.

[RunningHard]

I have a 5.9 Cummins in my 36’ rig. I pull a toad or a trailer with a RZR all over the NW. Not first to top of mountains, but not even close to last. Run 62-65 most of time, but will run 70 in parts of country. Have no complaints to date. More power would be nice at times, but not a big deal. Others may have opinions....��

[followingsea]

Originally Posted by RunningHard

I have a 5.9 Cummins in my 36’ rig. I pull a toad or a trailer with a RZR all over the NW. Not first to top of mountains, but not even close to last. Run 62-65 most of time, but will run 70 in parts of country. Have no complaints to date. More power would be nice at times, but not a big deal. Others may have opinions....��

Me too, also in the PNW. Love my 5.9L ISB with a Banks power pack for 300 HP. 175k miles.

If you think a MH is a sports car you would be wrong. That is my TOAD.

[banjopickin1]

No complaints here. We live in Western NC which means every trip in any direction involves mountains. Like Runninghard said, not the first to the top but not the last. Gets the job done pulling a TOAD with good fuel mileage.

[Randy125]

The 5.9 ISB is a good engine. I would look at the weight that the engine has to move and try to stay at or less than 1000 lbs to 1 horsepower ratio. In my opinion the remarks about mountain driving mostly don’t really stack up because most mountain passes have switch backs that usually limit your speed that you will probably be driving the speed limit anyway.

[Ljwt330]

I've had the ISB in a class A and now have the ISL. No complaints at all with the ISB and, as others have said, it gets the job done, is a proven workhorse and parts/service is a bit more available as it was the common power plant for Dodge pickups.


I would, however, use the rule of thumb of 1 horse power for every 100 lbs. of GVW. You will get up the hills just fine, regardless. I would look for an Allison 3000 series transmission with 5 speeds, at least, if possible. Don't know if the 6 speed is mated to the ISB or not. I do know that the ISB does not come with the engine brake, but does come with a very effective exhaust brake. Both work well.

[Crasher]

Our 96 36' Discovery had the 235hp 5.9 Cummins. I towed a Saturn with it and it took us where we wanted to go. Then our 39' Bounder had the 275 version of the 5.9. It also did the job for us towing a Chrysler minivan. Any coach that has the 5.9 engine will get the job done. With some, you will be slower that others going up the mountain, but that is a great time to take in the view. I could never understand the need for speed in a motorhome.

[Dutchv]

Originally Posted by ray999

Can you give an idea of the make and size of the coaches? Not sure if 300 has enough power.

It is a 36 ft Fleetwood discovery, with a 300 horse Cummings. My question is is this the 5.9 L or what leader is this.

[Ray,IN]

Originally Posted by Dutchv

I’m in the market for a new motorhome, I’m looking at a couple with the 300 horse Cummings, I was wondering is this the 5.9 L ISB
Any feedback would be great thanks

It will be a Cummins 6.7 ISB engine. It is a good solid engine, however it is under-powered for a 38- 40' MH IMO. My reasoning, it has lower torque than a larger displacement engine, and there is no substitute for torque.
The rule-of-thumb for powering a MH is no less than 1 HP per 100 lbs. if the driver wants to feel comfortable when climbing hills.
Don't take that wrong, the 6.7 will get the coach up the mountain, just slower than than nearly all other traffic.

[Gary RVRoamer]

The 5.9L and 6.7L are both the Cummins "B" engine but in different generations. The 5.9L ISB was typically rated at 275-300 hp in the early 2000's, and the 6.7L ISB was mostly rated at 340, but there were other Hp ratings available (different tune).


Discoverys used the 5.9L engine up thru at least 2000. Then they switched to a Cat 330 and later to the Cummins ISC 330 or 350. If you could give the year of the Discovery, we could stop guessing and look it up on the Fleetwood brochure website or at the Freightliner chassis website.


https://www.fleetwoodrv.com/shopping...arch/brochures

[Randy125]

Originally Posted by Ljwt330

I've had the ISB in a class A and now have the ISL. No complaints at all with the ISB and, as others have said, it gets the job done, is a proven workhorse and parts/service is a bit more available as it was the common power plant for Dodge pickups.


I would, however, use the rule of thumb of 1 horse power for every 100 lbs. of GVW. You will get up the hills just fine, regardless. I would look for an Allison 3000 series transmission with 5 speeds, at least, if possible. Don't know if the 6 speed is mated to the ISB or not. I do know that the ISB does not come with the engine brake, but does come with a very effective exhaust brake. Both work well.

Larry is correct on the weight to power ratio I must have had a fat finger.