Cummins N855.

[nabb]

Hello, its good to be back. Well l am looking for advice on how to marinize a natural aspirated Cummins N855. First, is it possible to change this industrial type to marine application? If the answer is, then what type of turbocharger and injectors can l use to refit this engine. All advice and recommendations welcome. Thanks.

Nabb

 

[C lectric]

I deleted my first posting as I missed that you want to change from an NA engine to a turbo engine.
Simple answer, yes an engine can be converted regardless of type. Whether it is worthwhile or not is another matter entirely. On older engines like this parts may no longer be available to do so. It may require a donor engine for the missing parts from a shop that does repowers.

If the HP change you want is large then a total rebuild may be needed as pistons are often different, Piston oil sprayers may be needed that are not used in a NA engine.



I think you are going to have to talk to a Cummins dealer and /or rebuild shop.
If the HP increase is moderate then only the turbo may be needed but I do not know which ones are suitable.


You will need water cooled exhaust manifolds.
You will need a heat exchanger to cool the coolant
You will need a raw or seawater pump to pump seawater through the heat exchanger
You will need a gear oil cooler to cool the gearbox.

The PT pump will need to be modified. This and how it is setup will determine how much fuel the injectors spray which will determine the HP developed.

THe PT may also need to be modified to operate as a marine engine.

THere are several different governor setups:

--Marine-- where once you set the rpms you want the engine to maintain, the governor will maintain those revs by varying the quantity of fuel to the injectors.

--Generator -- where the speed is set for one speed to suit the generator. The PT will vary the fuel feed to maintain those revs as the load varies. But you have no control of the revs other than the generators needs.

--Truck -- Where the load and revs vary so the PT pump responds to the drivers foot to increase/decrease the fuel. But the PT will not do it automatically as in the marine version. This can be worked through and has been done with possibly more throttle adjustments.

-- Industrial -- I don't know where or if there are differences here which may well depend upon the specific use the engine was set up for. A water pump may be very similar to a generator setup but I don't know.

There is one owner here, Simi 60, who has one of these engines. But if he can help you I don't know. Maybe he will reply or you could send him a PM.


Thats' all I can think of at this time.

 

[Gdavid]

Staying with a NA configuration and using a dry exhaust / keel cooler set up would make your project far less complex.

 

[woolf]

Staying with a NA configuration and using a dry exhaust / keel cooler set up would make your project far less complex.

That sounds like a sensible approach. We have this configuration in a twin 195hp @ 1800 rpm set-up, and are very happy with it.

 

[Simi 60]

.

There is one owner here, Simi 60, who has one of these engines. But if he can help you I don't know. Maybe he will reply or you could send him a PM.

.

Can't really help much but what reason do you have for wanting turbo?

Ours is a turbo variant, NTA 855m but reality is that I doubt the turbo does much if anything for us as we rarely run harder than 1250rpm, 1150 rpm is the norm.

 

[kapnd]

Hello, its good to be back. Well l am looking for advice on how to marinize a natural aspirated Cummins N855. First, is it possible to change this industrial type to marine application? If the answer is, then what type of turbocharger and injectors can l use to refit this engine. All advice and recommendations welcome. Thanks.
Nabb

I’m sure it can be done, nothing is impossible!
But it will be complicated and expensive, and the end product will still be an outdated motor, with inherent parts procurement difficulties, and nobody but you will venture to work on it, much less buy it if you decide to sell.
Sounds like you must be handy with the wrenches, why not buy a couple of used B or C Cummins marine motors and build a good one out of the parts?
I’ve done exactly that numerous times, with great success, and very low cash outlay.

 

[Simi 60]

But it will be complicated and expensive, and the end product will still be an outdated motor, with inherent parts procurement difficulties, and nobody but you will venture to work on it,.

Parts are very easy to find and cheap.
Engines are relatively basic with no electronics
New ones are still being made today, so hardly outdated.

Engines are being used all over the world in mining sites, generators, pumps, trucks and commercial vessels so finding someone to work on them is relatively easy

 

[Jmarsh203]

Like gdavid said, dry stack exhaust, keel cooler, and add a marine gearbox and that’s about all that’s needed to put it in a boat. Now adding a turbo and getting more hp that may be more complicated, not acquainted with a naturally aspirated 855 but you may need different fuel pump, injectors, pistons, head, cam plus’s all the intercoolers and other assorted turbo stuff. Is it a big cam or small cam 855? That would be the determining factor on if it would be worth adding a turbo, The small cams were turds. May need none of those things though idk but many times those are the differences between the turbo and non turbo variants. Seen many many 855 big cams turbo motors, prob the best of the last generation of mechanical injection engines ever put into anything. Parts still super easy to find and very cheap, easy to find people that know how to work on them, and amazingly reliable. I’ve got no clue what these other people are talking about it being outdated or hard to find parts but an 855 big cam is a much much better engine than a B or C series, anyone who says differently doesn’t know much about them, they also all came out at about the same time period so they aren’t any more outdated than a 12v Bseries or a C series.

 

[Ken E.]

Cummins sells 855 Recon (remanufactured) engines which would be great for a repower. These are beefier than I thought, at 14 liters and 3100 lbs bobtail.

https://www.cummins.com/engines/n855

 

[Choices]

I worked for Cummins and did this for several shrimp boat owners, forty four years ago. Used parts are out there and very cheap.

With the net finding them should be easy.

None wanted the turbo, and the engines ran at low rpms compared to highway use.

Once you have the part numbers you can find everything pretty easy, heads, pistons, castings, etc.

Very tall compared to a vee. Most went with dry exhaust.

 

[roddy]

Cost for marine conversion will be prohibitive unless you have donor marine engine. Marine parts will be hard to source as all the new stock was gone 25 years ago.
Believe NH 855's have been out of production for years... Guess its possible for new engines to be produced for special customers. Some military vehicles still get new VT 903's from Cummins. Definitely not great engine.
Big Cam 1 started in 1976. Big Cam 2, 3 and 4 followed until introduction of N14. N14 looks like and is based upon 855, however block, heads and front gear set were redesigned, its an electronic engine and most parts are not compatible. N14 was the best engine Cummins built IMO. Years of working the short comings out of NTC series, paved the way for N14's.
However there are marine NTC's, NTA's and N14's available from repowers.
They are a very reliable long living marine engine when conservatively rated.
NTA 370's was the highest recreational rating. There was a truck NTA 420 that had longevity issues.
Think highest marine continuous duty was 270 hp??
These NH, NTA and NTC's engines were already in service when I started working with diesels in 1973.

 

[Simi 60]

Cost for marine conversion will be prohibitive unless you have donor marine engine. Marine parts will be hard to source as all the new stock was gone 25 years ago.
Believe NH 855's have been out of production for years....

Maybe read the earlier posts?

As a starting point, brand new NTA855m with all the marine bits right here.

https://www.filterdiscounters.com.au/cummins-nta855-m350-marine-engine-brand-new/

Brand new N855 with all the bits here
https://www.cummins.com/engines/n855-ccec

And obviously, parts a plenty.

 

[nabb]

N855

Thank you all for your advice concerning the turbo issue. I do not think it would be an advantage to go turbo from what l have learnt from you. So I have decided to take your advise and forget about the turbo. And rather use Dry Exhaust and keel cooler on the engine. Thank you.