VT-903M engines

[rufuschamblee]

I ahve VT-903M engines and TD 509 2:1 Gears 1975 42 C. I would like to talk to anyone with this configuration about HP ratings and CPL numbers . Mine were 400HP at 2600 RPM original. Previous owner had them set to 2800 RPM trying to get 425 hp--is this possible? Second, what are the corect prop configurations? My e-mail is rufusm@elcoyote.com

[tony 275]

The CPL,arrangment,or serial numbers can only be interpreted by a dealer.These engines will turn considerably faster than the stock 2600RPM's.The U.S.Coast Guard runs them in all their 42' utilities,and they are governed at about 3600RPM's.I'm sure you have noticed 42UTB's hooked up wherever they go,they are constantly cruised at 2600RPM's,and may be run at 3600RPM's for a period of 45 minutes only with the boat's engineer in the engine room monitoring the engines.These procedures where related to me by a friend in New London who is a retired engineer on a 42UTB.He wasn't sure what the horsepower rating was for these engines,but he said they were very reliable run in this manner.Between building Cummins engines for boats and drag strip trucks,I can tell you that the 855ci NTC can reliably and safely be built to 500hp,and I have seen them built to 800hp,and run every day and these are 6 cylinders.Rail pressure,injector size and ignition timing,and turbo boost,are the important the important factors in building more horsepower in your engines.Timing being the most crucial factor,Cummins uses 3 timing settings slow,fast and nominal,they must be right or the engine will suffer piston failure,or broken head bolts.So yes,your engines can be safely built to 425-450hp,by a knowledgable Cummins mechanic,they can turn faster if you wish,and your props I would guess at 400hp,and 2 to 1 are probably 24"X 28". Tony

[DeeRow]

Tony,
I'm considering buying a 42C with VT-903 engines. You have posted that the VT-903 is a good engine provided that it has good maintenance. Can a "good" engine survey uncover an engine that has been poorly maintained? How can I find someone who can provide a "good" survey for a VT-903 (or how can I find a good VT-903 mechanic)? If a VT-903 has been abused, can it be fixed at a "reasonable" cost? I live in Stuart, FL (you posted recently that you delivered your boat here). A local mechanic suggested that rebuilding a VT-903 can cost as much as $40K!!!

[tony 275]

One of the most important things to look for when surveying a big block Cummins is the condition of the coolant,particularly the PH,you can do this yourself by going to a Cummins dealer and buying a coolant test kit,they are very inexpensive and you read it immediatly.Open one of the oil fills on each engine and run your finger around under the valve cover to see if there is any sludge.Black and thick is poor oil change duration gray and thick is more than likely,bad liners or liner packings.The only way I could possibly imagine spending that kind of money on these engines is by replacing all the peripherals as well.The actual ordinary engine internals that are routinely replaced during an overhaul are VERY reasonable especially when purchased from a national fleet supply company.These engines take to an in the boat overhaul very well,because the block is extremely under stressed.Yes there is an excellent Cummins mechanic that specializes in 903's in Stuart,I don't have his card on hand,but I will get back to you.There are a lot more of these engines in the Palm beach-Stuart area than you realize.A lot of the 70's-mid 80's Monterey's,Merritt's.Rybovich's still run them. Tony

[DeeRow]

Thanks, Tony.
If you would rather not post names in a public forum, please send email to me at markdesrosier@hotmail.com
Mark

[rufuschamblee]

Tony,

Would like to talk to you about increasing HP on VT 903's. If you give me your number I"ll call you.

Rufus

[Daryl]

Can you help me find the torque rating (ft-lb) of the VTA 903 TR engine.
Thanks Daryl

[DaveP3]

Tony,
I am not sure who your friend is and what his experience with Coast Guard UTB's is but having run a 41 UTB with 903's (Never heard of a 42 UTB, not familiar with them at all) for over 10 years I have NEVER, NEVER seen nor heard of 903's running 3600 rpm's. At least not turning 3600 and staying together. Maybe I was never in the right spot, but 2400 was normal continous max and 2800 was absolute max. While I do agree with the 425-450 max hp rating (I think the CG ones were between 415-430 depending on who did the rebuild). If there are any certified Cummins mechanics, you can probably clarify, but coming from the factory none were rated over 425 I don't believe.

If you are looking at a 903 powered boat I think personally I would shoot for a cruise of around 2100-2200 and a max of around 2500-2600. Even the Cat 3208 which is a smaller stroke motor peaked out at around 2800 rpms. I think operating the 903's above 2100-2200 for sustained periods is asking for trouble. Remember the CG has mechanics and a government budget to repair and rebuild their engines, unless you want to be like the CG who routinely (at least in my experience) rebuilt their 903's after less than 700 hours of operation. This was mostly due to the fact that they are run hard in response situations. No marine diesel can sustain continued high rpm operation without continous maintenance and frequent rebuilds.

Bottom line is if you have unlimited funds(like the CG) then go ahead and plan to run 2600-2800 all the time. But be prepared to shell out for repairs and rebuilds as often as the CG does. In my opinion the 903's are decent engnes, but Cummins saw fit to discontinue them for smaller, more powerful C Series electronic engines to meet EPA and Global pollution specs. Sort of like the old 2-stroke DDC's, good engines but old design and no longer made.