Cummins V8-300-M

[SeaEric]

Does anyone here have experience with the old 1970's vintage Cummins, I think the model is V8-300-M? This is a 300 HP, non turbo that I believe to be the same 785 cubic inch V-8 block as the turbo VT-370-M which is 370 HP. I realize that these are heavy, old, for the most part old technology with not much horsepower for their weight. I also understand that internal (rebuild) parts, although expensive, are still available. Some of the externals like heat exchangers are no longer available new, but some good used stock exists. What I want to know is: are there any inherant problems, known defects, scary stuff to be concerned about in owning a boat powered by these old motors? Are they any better or worse than an old pair of GM 8V53's of the same vintage? The boat in question is a 1970 model in beautiful cosmetic condition, well maintained as far as is apparent (pre survey) and the subject engines have 3200 original hours since new, never rebuilt. Any thoughts, comments, observations?

[SKYCHENEY]

I may be wrong, but I believe that the Coast Guard runs a bunch of these old Cummins still. I'm not sure which models, but it has been said that they also have many of the spare parts tied up for their own use. I believe that these are good engines because if they were not, you wouldn't see the Coasties still using them.

[Banshee36]

Would that be the famous 9 0 nothings?

[SeaEric]

I assume that you are referring to the 903, which is a 903 cubic inch engine. If I understand correctly, the 903 was introduced later, after the V8-300 and VT-370, but I may be wrong about that. Still lots of those old 903's out there crashing around the seascape, for sure.

[mstailey]

SeaEric;
Shoot DLCameron2 a message. He's a great source for Cummins.

Sky Cheney;
That would be the Cummins VT903M used in the Coast Guard 41UTB. Very much in use today. Great engines for those who know what they're talking about.

[mstailey]

You may also want to try Cummins - Bridgeway LLC.
3 Alpha Drive
Pittsburgh, Pa. 15238
(412) 820-8300

[SKYCHENEY]

There was another VT that shared many of the same parts with the 903. I just can't remember the model. If you call your local Cummins dealer, they are usually pretty good about sharing info with you, especially if you have serial numbers off the the engines

[mstailey]

Sky Cheney,
That would be the VT555M engine.

[dsharp]

Seaeric, You're right, it's is the same engine as the 370 hp but naturally aspirated; My dad repowered several boats with them years ago and they hold up fine. It's an earlier engine than the 903 series. In my opinion it's a hell of alot better engine than an 8-53. Doesn't sling oil everywhere. You can still get parts for them. Some people didn't like the capitol gears that they put behind them; they didn't shift as fast as an allison. It took them about 1-2 seconds to shift from forward to reverse. When you're about to hit the dock that seems like an eternity. He still has one in the barn that has been rebuilt with a new crank in it. Needs new heads. I didn't get them drained in time and I let it feeze and it cracked a head and the circulating pump. He's still bitching about it evertime he walks by it - it was only about 25 years ago.

[Avenger]

Would that be the famous 9 0 nothings?That's funny, I thought that was just a local expression here on LI. Knew a guy who had one in a truck, put bearings in it every 30K miles. :(

[Avenger]

Sky Cheney,
That would be the VT555M engine.Are you sure you're not thinking of the 504? I know they share the same stubby 5/16" plunger injectors, but the 903 has regular PT injectors. But I'm not an expert on Cum-a-parts, so you may be right. However I think it's a long way from the triple nickel to a 903 if we're talking cubic inches (I can assure you it's not horsepower). :confused:

[AquaNav77]

As the new kid on the Hatteras Owners Dock, this is my introductory reply to a thread. The Cummins V8-300-M was the predecessor to the 903. As stated, it is the non turbo version of the VT8-370-M. Both of these engines were 785 cubes in displacement and both rated at 3000 RPM. At that time the Cummins 300 and the 8V53 were considered to be medium duty engines hence their high RPM. The Cummins 300 had over the 8V53 much quieter operation and better fuel consumption because of its 4 cycle nature. The Cummins engine was heavier than its DD counterpart and both were available with the Twin Disc 506 marine gears. The Cummins engine was also available with the Capitol gears. Longevity should be rougly the same and parts are expensive and sometimes difficult to locate for both. BTW, the Coast Guard never used the 785 cube engine. They started using Cummins engines in their patrol boats when the 903 came unto the market.

Jim

[hatterasboatguy]

I had one of those vt903 engines in a semi..and the only thing I would ever use one for now would be to {a} tie a rope to it.
{b} throw it in the water
{c} tie the other end to my cleat
{d} go fishing!
Jim

[TGarth]

As the new kid on the Hatteras Owners Dock, this is my introductory reply to a thread. The Cummins V8-300-M was the predecessor to the 903. As stated, it is the non turbo version of the VT8-370-M. Both of these engines were 785 cubes in displacement and both rated at 3000 RPM. At that time the Cummins 300 and the 8V53 were considered to be medium duty engines hence their high RPM. The Cummins 300 had over the 8V53 much quieter operation and better fuel consumption because of its 4 cycle nature. The Cummins engine was heavier than its DD counterpart and both were available with the Twin Disc 506 marine gears. The Cummins engine was also available with the Capitol gears. Longevity should be rougly the same and parts are expensive and sometimes difficult to locate for both. BTW, the Coast Guard never used the 785 cube engine. They started using Cummins engines in their patrol boats when the 903 came unto the market.

Jim

I have a 1970 Hatt 53MY with the Cummins VT8-370-M engines and I believe the transmissions are the Capitol Gears variety. Do you know if there were certain Capitol Gears transmissions used? I can find no plate on the transmission and the only piece of paper around the boat says it is a Capitol Gears 12400, but I can't find any info saying they ever produced at 12400. Would love to lay my hands on a manual or even a list of quantities! BTW, my engines were rebuilt about 15 years ago and just keep chugging along. No issues so far. Touch wood.

[Avenger]

I had one of those vt903 engines in a semi..and the only thing I would ever use one for now would be to {a} tie a rope to it.
{b} throw it in the water
{c} tie the other end to my cleat
{d} go fishing!
Jim

That was about all I heard of them in trucks as well. Main bearings every 30K miles. They didn't call them the 9-0- nuthin' for nothing. Marine and military applications seemed to fare better.

Quick trivia. If anybody remembers the TV show Movin' On with Claude Akins playing Sonny Pruitt they had a Kenworth with a Cummins. The show only ran two seasons. In the first season you could see the big proud numbers on the valve covers whenever the hood of the truck was open, 903. The second season, the V-8 was gone and there was some variant of the venerable 855 in it's place. Apparently it didn't even hold up well enough for a TV show where the truck didn't actually have to do any real work.

[hatterasboatguy]

The best advice anyone could give you regarding the eight cylinder Cummins engines is to run like the wind.
Cummins knows how to build motors however they do not know how to build V-8 engines. I owned one in a truck the replacement parts were hideously expensive hideously hard to find and when you were done you still ended up with a heavy expensive to repair piece of junk. They are heavy they don’t have much horse power
and they eat fuel like I eat turkey at Thanksgiving in other words don’t buy it.