difference in noise level between Perkins 6.354 and DD 453

I haven't had the opportunity to hear the two in a close enough time span to say whether the DD was significantly louder. I'm not talking about the exhaust note but rather the actual engine noise inside the cabin/ER. I was on a boat a while back that had a freshly rebuilt 6-71N and remember being just floored by how SMOOOOTH it was even at dead idle. It didn't seem abnormally loud in the engine compartment but I was wondering if that could just be perception because the boat wasn't moving with engine vibes at all. While I'd not repower my 34' with a 6-71 a 4-53 could be on the list esp. as cheap as they can be had.

The oldfishboat has a 453 DD na. Its quiet at idle and smooth through its RPM's. Its keel cooled dry stacked, the noise through the exhaust and out the end even pushing hard is quiet. Good mufler.

The noise level produced by the motor itself under load is not too bad up to 1600 / 1700 rpm. Still hear radio have a conversation in the house.

But over that its a screamin Jimmy. Insulation sure helped but they are loud at higher RPM.

Is what it is realy no secrets.

My experience any way. The tug here has a 471 DD na and I find much the same with it.

The Eagle's 671 idles in gear at 500 rpm with no movement. Cruise is 1500 rpm and it does not move. The 671 is hard mounted, so if it did move then there is a problem. However the gen set is soft mounted on rubber/springs so it does move.

So it might be the way the engine is mounted?

The Detroit's are all 2-strokes and of course they have twice as many power strokes as 4 strokes. Also (for the same power) the "strokes" are half as intense. The 3-71 has as many power strokes as a 6 cyl Lehman or a 6 cyl Perkins. A 4-53 has the same power stokes as a straight eight Buick. A 6-71 is like a twelve in this very important respect. To have a boat engine as smooth as a boat w twice as many cylinders is a very nice feature.

No question that have a love it or hate noise level

Detroit's are smooth, but they have a sound that just seems to penetrate. This may be the reason I cruise at 1800rpm instead of 2300. I think the noise emanates from the roots blower mostly. The exhaust note I think is very pleasant on the 453. My boat is big enough and well enough insulated that the db level is not an issue. It's the busy bee screeming that has you looking at the tack to verify that the damn things are only spinning 1800.

so even the 4 cylinders are smooth at idle? That's good to know because from personal experience I know there is a HUGE difference b/w Cummins' 6BT and 4BT engine's vibrations.
Anyone here running a single 4-53N who would share some GPH figures and boat specs?

Detroit specs

I will post fuel and hp specs tomorrow after scanning them out of my orignial GM manual. One of the major reasons that the 2/53-3/53-4/53 run so smooth is they run a balance shaft similar to many of the new 4 cylinder gas engines. The 53 series engine was first introduced in 1958 and is the most modern of the Detroit series 2 strokes. It has a four valve head, is of modular construction, meaning it was configured as 2-53n-3/53n- 4/53n 6v53n- 8v53n and turbo charged 3/53t-4/53t-6v53t-8v53t-12v53t. They were being built into the late 90's and may be still available in electronic form for the military. The 4/53n depending on injectors developed between 112hp and 124hp @2800rpm. The 453t was rated at 180 hp. The 453t silver series had many improvements and is actually 6db quieter and 15% more fuel efficient than the 4/53n. In spite of their noise these are very durable engines. My boat was built in 1976 and my engines are running original heat exchangers , manifolds, starters, alternators, circulation pumps, and all castings. One engine was rebuilt in frame after a blower came loose off the Baha coast spraying the engine room with oil. They tightened it back on and continued on to Seattle where North Harbor rebuilt it. The the other engine is untouched and I think runs better than the rebuild. I'm pushing a 66,000lb boat cruising at 1800rpm 7.5 knts if I crank it up to 2300 rpm I get 10.5 knts.

"One of the major reasons that the 2/53-3/53-4/53 run so smooth is they run a balance shaft similar to many of the new 4 cylinder gas engines."

A balance shaft is part of the Series 50 DD , 4 cylinder diesel.

For simple smooth 3 cylinder or a multiple of 3 is best

FF

So FF are you saying that the 353/371s would be even smoother than the same engines in 4 cylinder versions? That is really interesting as the more I consider a repower the 100HP 353 seems even more fitting for my 34' trawler. The 220HP Perkins is absurd. I am perfectly happy with my boat at 9 kts for a top speed. The difference between 9 and 12-13kts is really noticeable in the boats handling. I'm sure trim tabs would make it feel more stable at those speeds but I didn't buy this boat to go that fast. I'd much rather get rid of the big assed Perkins and its associated intercooler, aftercooler, multicooler, turbo plumbing and in the process simplify my power plant and gain some engine compartment space. Now don't get me wrong my engine now doesn't leak or burn a drop of oil, fires up in the blink of an eye and has less than 2K hrs on it, I'm just the type who is always looking to improve upon what I have for one reason or another. Sometimes I'm the only one who can see those "reasons".

DD two strokers will burn more fuel. Peruse boatdiesel.com and you will see a lot of statements about replacing DDs with a 4 stroke saved 20+%. The same was found in power generation and diesel driven pumps decades ago. DD two strokers died for very good reasons long before cleaner exhaust demands came along. This revolution started 35 years ago and was at its zenith by the late 80s when Cat and Cummins and GM themselves had ample evidence for saying "buy our four stroke."

Twisted, to change out a perfectly running four stroker for a DD two stroker would be like, well giving up your internet connection where you heard it was a good idea. Hummm

It might be cheaper

If all you want is a larger engine room, it might be cheaper to trade up to a bigger boat. I don't think making this kind of swap is a move forward, more of a step sideways.

Fuel consumption is only one relatively small part of trawlering cost and I know I'd go for a 53 series DD just to go from rattle rattle rattle to VEROOOOM. Now that I know they have balancing shafts......
Vibration is a much bigger issue w me than 20% of fuel burn so I'd consider it a very big plus to have a smoother boat and my Willy is about as smooth as a 4 cylinder diesel powered boat could/should be. The serious scream'in noise I can do without so if I could run one like Scary does I'd be in.........but not to the point I'd start jerk'in my engine out or pay'in to have it done. I think Detroit Diesels are under rated like wood boats. They have a lot of nice features.
I disagree w you FF about the smoothness of 3 and 6 cyl engines. A good place to experience and evaluate engine vibration is sitting on a motorcycle, or should I say sitting on an engine. A vehicle w an engine that is much heavier compared to the total weight of the vehicle has much more vibration when you come in contact w it. I've run many 3 cylinder motorcycles....2 stroke and 4 stroke. The 750 Yamaha triple was known for it's odd vibrations. The 3 cyl 2 strokes were smooth except for their slight buzzyness at very high revs. The 3 cyl BMW was unbelievably smooth but it not only had a balancing shaft or 2 it had a gear driven counter revolving flywheel. But w unaided (vibration wise) motorcycles the 4 cylinder engines were all smoother than the threes. I know there is a reason why 3 cyl and 6 cyl engines should be smoother than 4 and 8 cyl engines but it is theoretical and dos'nt measure up in practice. And I think the theory only applies to revolving mass caused vibration.....not torsional vibration. So your 6 cyl Cat is NOT going to be smoother than an 8 cylinder. Power strokes closer together is king in the vibration world but crankshaft configurations can make a big difference w engines that have the same # of cylinders. A 4 stroke twin w pistons up together or pistons one up and one down is a good example. But a 6-71 with as many power strokes as a 12 cylinder engine and a big heavy flywheel is going to be smoother than an 8 cyl Cat. But w most engines it's just number of cylinders. All the above is of course just my opinion.