Detroit two stroke

Scary,
Where do you come up w the 124hp?

Are you looking on a chart that tells how much power that engine develops at 2400rpm?

"urban legend" Haha It's what I hear and read. I talked to a man on BoatDiesel that said he thought that Detroit Diesels (NA) are about the same as an old Lehman....(16hp per gal per hr). The fellow talked like he was very knowledgable and said that the boat I was looking at w a 4-53 would burn about exactly as much fuel as a Lehman in the same boat at the same speed. I think the DD would suffer a bit more at low loading though. Sounds like you run yours at about 60 to 65% load so you're probably doing better than most DDs.

But compared to a newer Cummins or Deere an excellent but old 6-71 should be about 25% less efficient. Don't you think?

The Hp numbers come from the Detroit engine manual

manyboats said:

Scary,
Where do you come up w the 124hp?

Are you looking on a chart that tells how much power that engine develops at 2400rpm?

"urban legend" Haha It's what I hear and read. I talked to a man on BoatDiesel that said he thought that Detroit Diesels (NA) are about the same as an old Lehman....(16hp per gal per hr). The fellow talked like he was very knowledgable and said that the boat I was looking at w a 4-53 would burn about exactly as much fuel as a Lehman in the same boat at the same speed. I think the DD would suffer a bit more at low loading though. Sounds like you run yours at about 60 to 65% load so you're probably doing better than most DDs.

But compared to a newer Cummins or Deere an excellent but old 6-71 should be about 25% less efficient. Don't you think?

Click to expand...

The fuel burn comes from my boat and digital tachometers and flow scans. There is also a boat review in Motor Boating and Sailing published in 1976 testing a sister ship validates my data almost exactly. Back to my original question which was if there was a difference between the old DD two strokes and four strokes of that era. It it sounds like not much. No doubt any of the new Electronically controlled turbo charged inter cooled engines will provide improved economy. It is interesting to note they actually built some turbo charge electronically controlled 6/53's probably for the military personnel carriers and the airline luggage haulers.

"Do you think the common knowledge is another urban legend?"

Are we back at Global Warming?

The Consensus is......

Fred... This thread is no longer in OTDE. Thanks.

manyboats said:

... will the real cause of the DDs lack of efficiency please step forward.

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Mythology. Probably created by people whose previous knowledge of 2-stroke engines was limited to the hideously inefficient and dirty loop scavenged lawn mowers of the day.

It has become a favorite past time to trash DDs "just 'cause." For many reasons they are a fun and easy target with few defenders other than users but if you are going to claim 25 percent worse efficiency then maybe there should be some data to back that up.

I suggest comparing BSFC of 2-stroke DDs and other engines of similar power. Keep in mind that BSFC is a moving target that varies with load.

"Keep in mind that BSFC is a moving target that varies with load."

And the higher the load the higher the efficiency on diesels..

DD's biggest problem was with folks that do not understand that a real engine is rated for cont operation on the pin, its max loading.

Under loading a DD , esp using an engine built for 180 to 230hp CONT as a 60 hp loafer IS a poor concept.

In most cases folks would be far happier believing DD , load a 71 series to 20 to 30 hp per cylinder and live long and prosper.

I have seen Displacement boats with a 6-71 , when the 3-71 would have been a far better choice.

Even when wide open a 6-71 would only add 1K or 1 1/2K to the speed of a displacement hull, so the "get home in bad weather " is pure nonsense.

Another aspect that is not mentioned may relate to the noise a DD 2-stroke makes.

A fair number of posters have mentioned in threads in this forum that going to high idle (full throttle at no load) is a frightening proposition. They are not comfortable with the noise and being close to a machine that makes that kind of unfamiliar noise. Because of the type of blower used, A DD has earned the nickname "screaming Jimmy" and when compared to a 4 stroke turning the same rpm, that sound intimidates some people.

Unfortunately those same folks believe the engine is about to destroy itself and so surely must be very inefficient if it converts so much fuel to noise. Do you think the manufacturers of competing 4-stroke engines went out of their way to correct the myths that surround the legendary Jimmy?

Look where DDs were most popular, look at the throttle response those applications required to be successful. Ever wonder why "boom boats" almost univerally use Detroits?

Frequently yachtsmen look at their power graph and see that their engine develops X amount of power at that rpm and assume that when they are cruising at that rpm that's what their engine is developing or as some would say "putt'in out". Not even close to true. An engine at 75% of max rated rpm is probably "putt'in out" well below 50% of rated power. I mention this as many boaters are under the impression that 50% of rpm = 50% of power. Far from reality but a common misconception.

Just say'in for the benefit of non gear heads.

This has turned into a very interesting discussion

My last boat was Bayliner 4788 With Cummins 330b's mechanical engine controls. I just spent a hour on Cummin's web sight reviewing 330B hp, prop load hp, fuel consumption, and calculated hp per gal per hour. It averages 18.5 hp gal per hour. A little better than the 453 Detroit at 17-18. When hatteras built the LRC series we were in a period of time when we had a fuel shortage and they were looking to maximize range and economy. All of these boat. with the exception of the 42 were underpowered when compared to the semi planing hulls. The 48 had the 453's the 58 came with 471/or 671 and the 65 with 671's. The 58's actually needed the 671's on the west coast to power though the rough conditions. All of these are operating at 60-80% at cruising speed. My tractors and trucks that had Detroit's all seemed to running at near max output , especially my dump truck. Power skiffs that purse seiners use to pull nets seem to like the Detroit's as well.

Well Scary I see the difference is smaller than I thought. Perhaps I should go look at that boat w the 4-53 again. No time for that now though. And a DD in Willy would need to be a 1-53 and I do,nt think it was made. 2-53 would be about double the power Willy needs but glad to hear the DDs are more fuel efficient than I thought. Perhaps I,ll have one one day.

PS...If the 4-53 boat had a 3-53 I,d be more interested.

manyboats said:

And a DD in Willy would need to be a 1-53 and I do,nt think it was made.

Click to expand...

Don't know about the 1-53 but Wikipedia says there was a DD 1-71. 10hp. Would that be small enough?

Your in luck

They were made is these configurations, 253,353,453 all counter ballanced, 6v53, 8v53,12v53. sliver models were turbo-d. But if I were to repower it it would be with one of the modern Jap marine engines. Why mess with old technology given a choice.

DD

Sure are smoky on start up. Our neighbors boat disapears on every start up until the wind blows the smoke away.

Were great engines and have lasted a long time in the industry.

Messy, I don't like working on them because they tend to be dirty.

Scary said:

Power skiffs that purse seiners use to pull nets seem to like the Detroit's as well.

Click to expand...

All the net boats on the purse seiners around here, or at least most of them, are powered by big automotive V-8s.

Scary,
How are the counterbalancers configured. Are they like counter rotating camshafts or what and how effective are they? Some motorcycles have counterbalancers and shake like they didn't and some produce unbelievably smooth engines. I had a 3 cyl BMW that was so smooth I rode it 10 miles at about 70mph in forth gear (it had 5) before I noticed the gear position indicator light said I was in forth. It even had a counter rotating flywheel to cancel the torque effect. But it would be hard for a 4 cyl 2 stroke to vibrate much as it has as many power strokes per min as a straight eight Buick.

And Scary........I have a nearly new Japanese engine and I know of nothing about it that is high tech. Don't want high tech either but I'm sure there are seals made out of better material, more modern thin-wall casting blocks, more advanced metallurgy and other details. One of the main reasons I bought a new engine was to get glow plugs and the instant starting they provide. But that's not a new feature.

Countrer ballancers are gear driven the reverse direction of the camshaft

I believe the machine tolerances are better on the new engines. Gaskets and seals as well. I have to agree that my new Northern Lights generator which is a Kabota triple shakes the boat worse than my old 36 year old Onan 4 banger. The Detroits are very smooth. No rough idle , no shake, they are as smooth as a new gas v8. This might be why heat exchangers and accessories last so long on them, they are not subject to vibration. My Cummins 330B's shook the boat so badly you had to get up to fast idle 800 plus rpm before the dishes fell out of the cabinets. Doors rattled the widows rattled. The gear train layout below Detroit Diesel 4 53 engine specs are found at Barrington Diesel Club, whose aim it is to provide technical data, specs and bolt torques relevant to Cummins, Detroit Diesel, EMD and ADE engines. Engine start up smoke" mine don't smoke on start up or for that matter ever. My Cummins did a little.

manyboats said:

But it would be hard for a 4 cyl 2 stroke to vibrate much as it has as many power strokes per min as a straight eight Buick.

.

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Eric-- The 70-foot or so long aku boats (tuna boats) in Hawaii from the late 1940s through the end of the 70s when I left were all powered with 6-71s (single engine boats). I went out on them on a few occasions filming and the engines were very smooth but very noisy (dry stack).

Scary,
Yes Yes on all of it. Good to hear some objective talk on older stuff. Especially anchors and engines.

I was especially interested in the heat exchanger and vibration issue you mentioned because entirely on my own intuition I decided the heat exchanger didn't need all that 4 cyl 4 cycle vibration and had my HE mounted on the bulkhead slightly aft of the engine. My HE lives almost totally w/o vibration. Don't really know if it's better off but you're speaking about it gives me a lift.

Marin those Jimmie's are sweet (smelling if they are worn enough) and I really like the sound but as you say they are noisy. However I think sound insulation CAN tame the beast in this regard. Perhaps the reason they are seen to smoke so much is that they probably run great even when worn out and people just keep running them. Take a little flack from the green guys, pour in a bit more oil and get several years more use out of them.

Theres a saying

There used to be a saying in the construction industry. If you can get a Jimmy to start you got another days work out of it. When I was a kid I liked the busy sound of a Detroit. I'm not as enamored with it at 68. Mine start instantly, virtually at the touch of the starter button. Good compression, valve and rack adjustment are the key. In cold weather block heaters help. You can tell a lot about a Detroit on start up when cold if they smoke or roll at idle they could be starting to age. If compression is a little low, or the batteries aren't up to snuff, they tend to flood as the injectors are pumping away until combustion, rich combustion blue smoke. Block heaters keep the oil thin and the combustion air warm, let's the starter really spin the engine. Mine fire off without even hearing the starter. I run the block heaters most of the year. Now that I'm in the Cal Delta If unplugged them for the summer as an experiment to see if they start harder without the heaters in the warm summer months . so far instant starts.

Why would you ever want to change?

Have you got the noise issue under control?

manyboats said:

Perhaps the reason they are seen to smoke so much is that they probably run great even when worn out and people just keep running them. .

Click to expand...

I do not recall any of the aku boats I was on back in the 70s being smoky, even on startup. They were definitely noisy but it was not an irritating noise so much as just a loud one. The dry stack and big muffler gave the 6-71 a deep but loud rumble more than a sharp, ear-splitting crack which is what I've heard 8V-71s sound like on several boats I've encountered here.

It severely pisses me off that I lived with and saw these boats almost every day for some 30 years and never took a single photo of them, even when I got into photography in my early teens. They are my all-time favorite boat. They were all built locally in the late 1940s, early 50s, and were designed specifically for day-fishing (no ice or refrigeration) in the very rough water around Hawaii including the notorious Molokai Channel.

I've been on them, filmed on them, knew some of the skippers and crews, guided them to tuna schools from an airplane, looked down on them from the plane when they were netting their live bait in Pearl Harbor every morning, and never took one damn photo. I guess I figured they'd be around forever and I'd take some shots someday. Then I left and now other than a couple of derelicts, they're all gone.

These two pictures were sent to me a few years ago by an acquaintance in Honolulu. But you can see the big muffler and pipe setup they had.

Noise is under control

Hatteras did a pretty good job on sound insulation.
the cockpit being the the worst.
DB at 1800 rpm my cruising speed
Cockpit 76db
Salon 72.5db
Owners state room 67db
Pilot house 62db
Flying Bridge 56-1/2db
Of course the sound is that busy Detroit sound. I feel you have to raise your voice in the salon.

Interesting hull design, very fine entry with a very full midsection and hard chines, I would think they rode very well.

Mine don't smoke. They might but buy the time I get them lit up and jump into the cabin and run outside to see the smoke there is none. My starboard motor is getting alittle blue smoke at idle. Blue smoke good or bad? That's the one I'm going run the rack on because I'm getting a little smoke somewhere out of the valve cover or somewhere around that general area.

Scary said:

Interesting hull design, very fine entry with a very full midsection and hard chines, I would think they rode very well.

Click to expand...

If you're talking about the aku boat, they actually rode fantastic. They sliced through swells and waves like destroyers. Not a lot of pitching. They rolled, of course, but they didn't roll fast. And the change of direction at the end of the roll was guite gentle.

The reason for this was the way the boats were fished. A narrow plank, about 14 " so wide, was fastened across the transom just above the waterline. A small piece of quarter-round lath was fastened to the outboard edge of the plank. When the boat found a school of feeding tuna (marked by birds or later, spotted by a plane), the boat was driven into the middle of the feeding frenzy and a guy in the live bait well aft of the pilothouse started shoveling baitfish over the side as fast as he could. The baifish, grocking immediately what was going on, ran under the boat for protection from the tuna. But since the boat was idling forward the bait fish all ended up at the stern.

Four to six fishermen would stand on the transom plank barefoot or in rubber slippers with their toes against the lath for "support." Each one had a short, stout bamboo pole with a short length of heavy line tied to the tip of the pole with a huge chromed barbless hook on the other end. The hook was flipped into the frezy of feeding tuna at the stern, a fish would bite, and the fisherman levered the fish over his head into the fish well behind him. There a guy would whip the hook out of the fishes' mouth, give a yell, and the fisherman would flip the hook back into the feeding frenzy and repeat the process.

There were no raiings or lifelines. Besides having a really good sense of balance, the design of the hull also kept the rolling of t

Scary said:

Interesting hull design, very fine entry with a very full midsection and hard chines, I would think they rode very well.

Click to expand...

If you're talking about the aku boat, they actually rode fantastic. They sliced through swells and waves like destroyers. Not a lot of pitching. They rolled, of course, but they didn't roll fast. And the change of direction at the end of the roll was guite gentle.

The reason for this was the way the boats were fished. A narrow plank, about 14 " so wide, was fastened across the transom just above the waterline. A small piece of quarter-round lath was fastened to the outboard edge of the plank. When the boat found a school of feeding tuna (marked by birds or later, spotted by a plane), the boat was driven into the middle of the feeding frenzy and a guy in the live bait well aft of the pilothouse started shoveling baitfish over the side as fast as he could. The baitfish, grocking immediately what was going on, ran under the boat for protection from the tuna. But since the boat was idling forward the bait fish all ended up at the stern.

Four to six fishermen would stand on the transom plank barefoot or in rubber slippers with their toes against the lath for "support." Each one had a short, stout bamboo pole with a short length of heavy line tied to the tip of the pole with a huge chromed barbless hook on the other end. The hook was flipped into the frenzy of feeding tuna at the stern, a fish would bite, and the fisherman levered the fish over his head into the fish well behind him. There a guy would whip the hook out of the fishes' mouth, give a yell, and the fisherman would flip the hook back into the feeding frenzy and repeat the process.

There were no raiings or lifelines. Besides having a really good sense of balance, the design of the hull also kept the rolling of%

Scary said:

Interesting hull design, very fine entry with a very full midsection and hard chines, I would think they rode very well.

Click to expand...

If you're talking about the aku boat, they actually rode fantastic. They sliced through swells and waves like destroyers. Not a lot of pitching. They rolled, of course, but they didn't roll fast. And the change of direction at the end of the roll was guite gentle.

The reason for this was the way the boats were fished. A narrow plank, about 14 " so wide, was fastened across the transom just above the waterline. A small piece of quarter-round lath was fastened to the outboard edge of the plank. When the boat found a school of feeding tuna (marked by birds or later, spotted by a plane), the boat was driven into the middle of the feeding frenzy and a guy in the live bait well aft of the pilothouse started shoveling baitfish over the side as fast as he could. The baifish, grocking immediately what was going on, ran under the boat for protection from the tuna. But since the boat was idling forward the bait fish all ended up at the stern.

Four to six fishermen would stand on the transom plank barefoot or in rubber slippers with their toes against the lath for "support." Each one had a short, stout bamboo pole with a short length of heavy line tied to the tip of the pole with a huge chromed barbless hook on the other end. The hook was flipped into the frenzy of feeding tuna at the stern, a fish would bite, and the fisherman levered the fish over his head into the fish well behind him. There a guy would whip the hook out of the fishes' mouth, give a yell, and the fisherman would flip the hook back into the feeding frenzy and repeat the process.

There were no raiings or lifelines. Besides having a really good sense of balance, the design of the hull also kept the rolling of the boat to something the fishermen could handle.

These fairly narrow boats were also quite fast even with just a single 6-71 as power. On occasion I'd be fishing off the north shore of Oahu or in the Molokai Channel with my friend in his 28' Uniflite and one of these things would pass us in search of fish or heading back to Kewalo Basin and the tuna canneries. It was like being passed by a freight train. We'd be bobbing all over the place like a cork as we trolled and the aku boat would sweep past us like it was on rails. Very, very impressive boats. The crews were almost exclusively Japanese. (Japanese Americans for the politically correct crowd.) At the back of the bridge on every boat was a small shrine to Buddha and the crews would light incense and place offerings for Buddha every time they went out.

Hatteras did a pretty good job on sound insulation.
the cockpit being the the worst.

Yachts \have to spend the bucks , and do the engineering required to quiet their engines.

Most of the "NOISE!" complaints come from commercial or converted military boats where , usally, nothing was spent on sound abatement.

Amazing what a couple of boat bucks will do to retrofit some silence.

FF

I would like to show a picture of Chip (Anode of M/V Scout) working on those little 453's while underway in 8'-12' seas religiously doing a engine room checks. It was my Hatteras 48' LRC that we took from Panama to Guatemala and I was very happy to have Chip aboard as first Mate/Engineer and friend. I would ask him to help bring my boat anywhere. I also included a picture of the crew at chow time in San Andreas along the way and one of Chip relaxing while off watch
Also included a picture of "Island Spirit" that got us where we needed to go.
God Bless those little 453's that hadn't run for 4 years. Before I bought the boat they towed the boat from it's anchorage to the marina and around in the marina to move slips. After we got them running (new fuel & dockside valve job) we took her over 800 plus miles and ran those motors over 130 hours in 10 days and they never missed a beat (I am a believer after that trip). After we got to Rio Dulce, Guatemala I had the compression tested and they were all over the place (some in the high 300's and some in the low 200's).
I will have them rebuilt in the upcoming fall along with the gears while in Rio Dulce by Rick Vera a trusted Detroit Mechanic with many years of experience.

Thanks Perry for the great compliments and the glamor pics.

As you can see, I had no problems sleeping with those 4-53's humming along right underneath me.

Here's my little 2-53!