Detroit Diesel 4-71 NA

[mike66]

Any general knowledge about these engines in general and suitability for pushing a Hatteras 58 at displacement speeds? I believe they are 175hp each. Not much extra in reserve I'd think, but maybe adequate for ICW/inshore cruising? Hours unknown at this point.

Thanks.

 

[Portage_Bay]

175HP seems high. Screenshot from boatdiesel.com

 

[C lectric]

If I remember correctly some of the Hatts., the LRC 58' used them. THe 65' LRC went for the 6-71s.

THose boats were intended to be slower passagemakers, not planing boats by any means.

I did meet someone that brought his 58 LRC to the Broughtons, mid west coast B.C. from Hawaii but that was 20 +yrs ago. He did have the 4-53s.


You might also consider looking up the Hatteras forum and asking there.

https://www.samsmarine.com/forums/index.php

 

[Mako]

@mike66, with over 450 posts you're not new here and I'm surprised you haven't read the many, many previous threads on Jimmies.

Personally I'm surprised they didn't put 3-71's or 4-53's in that boat. My 65 footer had twin 6-71's and it was way over-powered. I wish I had a single 6-71 instead. I ran 1325 rpm at 8.25 knots and did not like running those engines so slowly, especially on those continuous, 5-7 day long runs.

 

[CaptBud]

Detroit 471 is more in the 130HP range. For a 58 footer you would need two

 

[mike66]

Just getting started on my research. Own a Lehman single and know quite a bit, but no reason to know anything about Detroits. The Hatteras has twins.
Just was looking for any feedback on general reliability such as Great!, Run Away! Easy to maintain!, nightmare!, that sort of stuff. I am a 95% DIY type of guy. Seems being NA it cuts down on some maintenance, probably overall engine stress by not being pushed to produce too much power.

 

[tiltrider1]

The 6-71 is probably the most common engine in the world. The 4-71 is basically all the same parts. I think this is a better engine than the 4-53 but we are talking insignificant differences. I see no reason to run and finding service and parts will be easy.

 

[Comodave]

We were looking at 53 LRCs a couple of years ago. It had 471s in it. They are a great engine, easy to maintain and parts are available everywhere and fairly reasonable in prices. I posted a speed vs rpm vs fuel burn that we found on one of them. I no longer have the table, when we decided to go with an express cruiser I deleted all the Hatteras stuff. You may be able to find it here on TF by searching, maybe. I loved the boat but my wife couldn’t get past how dirty it was so we didn’t make an offer on it. Great layout.

 

[Alaskaflyer]

We were looking at 53 LRCs a couple of years ago. It had 471s in it. They are a great engine, easy to maintain and parts are available everywhere and fairly reasonable in prices. I posted a speed vs rpm vs fuel burn that we found on one of them. I no longer have the table, when we decided to go with an express cruiser I deleted all the Hatteras stuff. You may be able to find it here on TF by searching, maybe. I loved the boat but my wife couldn’t get past how dirty it was so we didn’t make an offer on it. Great layout.

https://www.trawlerforum.com/forums/showpost.php?p=960423&postcount=3

 

[Mako]

8 knots 1400 rpm. Seems like an ideal point

 

[sbman]

71 series Detroits are great for a DIY guy. I've got a thread here detailing an overhaul of a 671, it's really the same engine, just two cylinders longer.

If have a bit of clearance in the engine room you can do an in-frame rebuild right there in the boat if you so desired. If you can find an old salt to show you how to run the rack and tune the governor you'll be able to do all your own work on one no problem.

 

[sbman]

Some how this was a duplicate!

 

[Mako]

If OP wants to run those 4’s a bit warmer (say 1600-1700 rpm) then it’s easy enough to use smaller injectors. Could drop the rating down to the 110-120hp range. Repitch your props.

 

[Comodave]

https://www.trawlerforum.com/forums/showpost.php?p=960423&postcount=3

Yup, that is it, thanks for finding it. And my thumb looks great, doesn’t it…

 

[Comodave]

71 series Detroits are great for a DIY guy. I've got a thread here detailing an overhaul of a 671, it's really the same engine, just two cylinders longer.

If have a bit of clearance in the engine room you can do an in-frame rebuild right there in the boat if you so desired. If you can find an old salt to show you how to run the rack and tune the governor you'll be able to do all your own work on one no problem.

In the 53 Hatteras LRC there is about 6’6”, or more, of headroom in the engine room. Quite a bit on the outboard side too. Great engine room to work in.

 

[Scooby5959]

71 series Detroit is probably one of the best engines ever made some I will argue the 60 series is better nevertheless one of the best engine that you could possibly have fairly easy to inframe as already been stated most of the people reading this form should be jealous of that Engine

 

[Mako]

Best of all, they are really, really quiet. Hence the double layer of foam earplugs and ear muffs that I always wore, just to be stylish of course.

 

[Comodave]

Best of all, they are really, really quiet. Hence the double layer of foam earplugs and ear muffs that I always wore, just to be stylish of course.

Ha ha, at least they have a throaty sound not an annoying whine.

 

[Lepke]

The inline 71 series are probably the most reliable Detroit, but 53s are a close second. I've been running them or most of 60 years, private, commercial, and in the military. If you learn the adjustments, they are very reliable, low maintenance engines. But don't let the average marina mechanic touch them. I suppose a marina mechanic could learn to change oil and with some instruction, the fuel filters. There is no bleeding necessary like injector pump engines.

If you keep the fuel and oil clean, once the adjustments are made, they go about a decade with just the occasional check. I run 2 micron fuel filters and haven't changed an injector since 2011 when I had these rebuilt. Until covid, about 500 hours a year.
My engine room is well insulated and directly under the salon. At full rpm, twin 671s, I can carry on a typical conservation. You push the button, warm them up, and go.

 

[DNT99611]

My old fishing partner has a 3-71 in a 53 foot skookum. Puts 6000 hours a year on it. Rebuilds it every 5 years. Engine has been rebuilt 3 times so over 100,000 on it. Not sure how you can get much more reliable than that. Trusts that engine all year long in the gulf of Alaska and the Bering Sea.

 

[mike66]

Thanks all. Very helpful. Now it's down to this particular vessel.
Love this forum! Guess I'll be spending time on Hatteras owners sites.
I may be two boat owner. My Albin 40 isn't going anywhere soon.
Our plan is keep a boat in RI and one in FL, and snowbird it. Funny cause we live oceanfront in RI. Gotta love the boating life!

 

[Mako]

@Lepke, my old Gray Marines generated about 16.3 hp/gal-hr but the more recent 4 valve head models were about 18-ish. These are all naturals of course.

I’m wondering if it’s possible to build an X-71 which is super efficient. Perhaps turbocharged for efficiency butwith tiny 45 injectors, to keep the power-rating down to 150-180 hp, and hopefully pushing 19+ hp/gal-hr.

What do you think?

 

[Comodave]

Have you founf a particular 53?

 

[Juliet 15]

I’ve owned a Hatt 58 LRC now for about 4 years with 4-71 naturals in it. It’s our 4th boat. I love these engines. Simple, super reliable, parts available, and yes - they’re loud.

They push the 110000 lb (full fuel and water, clean bottom) boat at 9.66 knots at about 1950 RPM.

If you want to talk more send me a PM I’ll give you my cell number.

 

[Lepke]

@Lepke, my old Gray Marines generated about 16.3 hp/gal-hr but the more recent 4 valve head models were about 18-ish. These are all naturals of course.

I’m wondering if it’s possible to build an X-71 which is super efficient. Perhaps turbocharged for efficiency but with tiny 45 injectors, to keep the power-rating down to 150-180 hp, and hopefully pushing 19+ hp/gal-hr.

What do you think?

If I remember right, the blowers produce about 6psi at full rpm. Normally a turbo Detroit has a lower compression ratio. With turbos on a natural you'd get much higher temps and combustion would be much hotter, shortening the time between overhauls, maybe burning valves and injector tips. And with smaller injector, a much lower fuel/air ratio. Fuel is part of the cooling. Fuel is passing thru the injectors all the time, cooling the tips between firings. And even though the fuel is heated from passing thru the head, it's 1000° cooler than the piston tops. And with smaller injectors you get some lesser amount of cooling. My experience with smaller injectors is loss of higher rpm. The governor doesn't know what injector is installed, so it just opens the injector as far as it can until it's wide open. It still takes fuel to create hp.
The nice thing about naturals is long life, at least 3x longer than turbo models. It probably costs a lot more to rebuild the engine than buying more fuel.

I get better mileage out of my engines by adjusting each cylinder to have the same exhaust temp by how I adjust the rockers, and I use a fuel conditioner (archoil AR6200) that does the usual stuff, but also makes the fuel combust better and gives me 6-10% better fuel economy depending on how much conditioner I use. And I have self made hydrogen generators that break down water into 2 hydrogen, 1 oxygen molecules that is fed into the intake. The hydrogen is additional fuel and the oxygen improves the burn. That gives more than another 10% improvement. So while I should be burning 6 gallons/hour per engine at 1800, I burn a little less than 4.25 gallons/hour. If I did the math right, about 30% better mileage.

 

[FF]

The usual of Thumb on 71 series is 20-30 HP per cylinder for long life.

The best operating range is 1200-1800 RPM


If starting one that has been out of service for 6+months be SURE to remove the cover and observe that all cylinder injectors are free to move.

If not a "stuck rack" (from one injector) could cause very high RPM with only cutting off the fuel or air to stop it.


The WWII Grey Marine instruction book is the best tutorial for 71 series and worth the purchase price.

 

[rslifkin]

If I remember right, the blowers produce about 6psi at full rpm. Normally a turbo Detroit has a lower compression ratio. With turbos on a natural you'd get much higher temps and combustion would be much hotter, shortening the time between overhauls, maybe burning valves and injector tips. And with smaller injector, a much lower fuel/air ratio.

The extra air should help keep combustion and exhaust temps down and avoid those issues. Adding turbos on the higher compression engine should be ok in that sense, you just can't fuel them as hard as the lower compression ones (so you'll get less power before starting to hurt durability). EGT gauges would probably be necessary to get the setup dialed in.

 

[Scooby5959]

The usual of Thumb on 71 series is 20-30 HP per cylinder for long life.

The best operating range is 1200-1800 RPM


If starting one that has been out of service for 6+months be SURE to remove the cover and observe that all cylinder injectors are free to move.

If not a "stuck rack" (from one injector) could cause very high RPM with only cutting off the fuel or air to stop it.


The WWII Grey Marine instruction book is the best tutorial for 71 series and worth the purchase price.

As close to 1200 as you can get would be my choice .Probably about 1400 if you get the power you need There

 

[Mako]

At what rpm is that big blower cooling down the block in an unhealthy way? I always felt my engines were happier at 1400rpm or higher.

 

[Mako]

I’ve owned a Hatt 58 LRC now for about 4 years with 4-71 naturals in it. It’s our 4th boat. I love these engines. Simple, super reliable, parts available, and yes - they’re loud.

They push the 110000 lb (full fuel and water, clean bottom) boat at 9.66 knots at about 1950 RPM.

@Juliet, what is your fuel burn at 8 knots?