The Most Reliable Diesel Inboard - (moving up MAYBE)

[RWS]

OK I'm anal, no SUPERANAL about the boat.

I am, however considering moving up in size

I realize this forum is not all about express cruisers, however thats what best fits my needs.

I continue to be delighted with the 15 year old Yanmar 6LP's that I purchased new, installed in my 38 year old boat.

FLAWLESS mechanical diesels.

NO electronics.

Other than normal maintenance, a started solenoid and one raw water hose (my bad) has been the only parts to fail in 15 years

Seriously thinking about moving up size-wize to a non pod drive express above 40' with mechanical diesels

Back in the 1980's I ran a fleet of off/on road Mack trucks and heavy equipment. Two shifts/day 5 days/week. Trucks were six cylinder inline mechanical diesels. I want no part of HDPI, electronic injection or computers in a wet, salty marine environment. Just mechanical diesels, pyrometers, Floscan & boost gauges.

In looking at the possibilities I'm going to start with the engines first to narrow the possible boat choices.

While I don't care about Tier I, II, II etc I'd prefer not to go prehistoric with a 2 stroke setup

I also want to avoid those power squeezed series that end up with a short life

I am SERIOUS and do appreciate your input.

BEST !

RWS
__________________
1983 Trojan International 10 Meter
Twin Yanmar 315 Turbodiesels
Solid Glass Hull
Woodless Stringers1983
Full Hull Liner
second owner - since 2001
Vessel Survived Hurricanes: Andrew Cat 5, Eye of Charley Cat 4, & Eye of Irma Cat 2
Was featured on the floor of the Convention Center - 1983 Miami International Boat Show
TROJAN INTERNATIONAL WEBSITE - www.TrojanBoat.com

 

[Larmex99]

Jumping in here as there has not been a response. If it was me I would start with determining which brand of engine is serviced in your area and then find out which of them are the most highly regarded by the boating community there. After that you should have a short list of makes that members of this forum will be happy to discuss.

 

[OldDan1943]

Readily available parts at a reasonable price.

I do agree with you, if possible a naturally aspirated engine.
One other point, easily accessibility for maintenance.

 

[twistedtree]

I personally disagree with the aversion to turbos and electronically controlled engines, actually preferring both. But your choice, your values.


For a 40+ foot express boat I think you are probably in the 500 hp range each with twin engines. I think all those will have turbo's, but you didn't mention and issue with them, so I'll assume it's only OldDan who doesn't like them.


Cummins would probably be my fist stop, but I don't know specific models in that power range. Cats too, but I know even less about their models. And obviously Yanmar. Maybe MAN, and probably MTU/Detroit. But I think to get a mechanical engine you are looking at an early 2000s or older build.

 

[RWS]

Thank you all.

I'm still in the learning phase of this exercise.

Seems that common rail has a better track record than I thought.

Turbocharged, intercooled diesels are a requirement in this size

The application is not a trawler, but rather a planing hull, express cruiser 40+ feet in length.

BEST !

RWS

 

[ktdtx]

The problem is that with planing hulls the engines have most likely been run more aggressively than on a displacement hull. The question is how much more aggressively and for how long and how have they been maintained. Not always easy answers available.


I wold think, nowadays, most express cruisers would have turbo/intercooled engines to get the HP needed.

I too believe that most of the electronically run, common rail engines have proven themselves to be reliable.

 

[OldDan1943]

I personally disagree with the aversion to turbos and electronically controlled engines, actually preferring both. But your choice, your values.


For a 40+ foot express boat I think you are probably in the 500 hp range each with twin engines. I think all those will have turbo's, but you didn't mention and issue with them, so I'll assume it's only OldDan who doesn't like them.

OldDan has a Cummins 380 (5.9 QSB.)
The turbo is just something else to go wrong while cruising. Without an operating turbo, I am not sure if or how the engine will behave, if at all possible?

 

[Comodave]

We just bought a Formula 41PC with 420 Cummins 6CTAs in it. I wanted Cummins. The other choice that Formula put in was Volvos. I will not own another Volvo. If a boat has a Volvo in it I immediately move on to another boat. Volvo parts are too hard to get and too expensive. For some parts it can take months to get and that can be half or more of a season here in Michigan. So far we love the Formula, great build quality and excellent support from Formula for a 23 year old boat. I could get new seat skins from Formula after 23 years, amazing.

 

[rslifkin]

OldDan has a Cummins 380 (5.9 QSB.)
The turbo is just something else to go wrong while cruising. Without an operating turbo, I am not sure if or how the engine will behave, if at all possible?

Depends on how the electronics are programmed. If they do a good job of referencing fuel to boost (which they likely do to avoid smoke), it'll probably run, just with error codes and greatly reduced power if it's not making full boost.

 

[GFC]

I had Cat 3406C's in the boat and now have a Cummins 340hp in the motor home. My experience with Cats was excellent. Never a problem with the turbos or any other parts of the Cats. In 10 years of cruising with them they performed flawlessly.

 

[twistedtree]

Thank you all.

I'm still in the learning phase of this exercise.

Seems that common rail has a better track record than I thought.

Turbocharged, intercooled diesels are a requirement in this size

The application is not a trawler, but rather a planing hull, express cruiser 40+ feet in length.

BEST !

RWS

I had a 47' planing hull boat for a number of years with twin Cummins QSC 500hp engines. Turbo charged, after cooled, high pressure injection, and ECU, so evil in every possible way. They were fantastic engines and I wouldn't hesitate to have them again.

 

[GoneDiving]

Jumping in here as there has not been a response. If it was me I would start with determining which brand of engine is serviced in your area and then find out which of them are the most highly regarded by the boating community there. After that you should have a short list of makes that members of this forum will be happy to discuss.

I'd agree and the easiest way to answer these questions is to walk down your local commercial dock and start asking questions when the guys aren't too busy. There is likely to be one or two common brands Their choices will be determined by operating cost, reliability and serviceability. Asking recreational guys introduces emotions and personal preferences. No offence to anyone but it's rare to find someone who spends $100k on engines in their pride and joy then admits it was a mistake.

I'd agree that a 500hp non turbo is going to be a serious lump of iron and that engine management can add to reliability. Look at a Toyota Camry vs a 30yo Detroit product. One just runs but isn't wort rebuilding when it does expire. The other is probably less reliable but is so easy to repair that it can be kept alive forever. Everyone's preference is different.

 

[Arc]

OldDan has a Cummins 380 (5.9 QSB.)
The turbo is just something else to go wrong while cruising. Without an operating turbo, I am not sure if or how the engine will behave, if at all possible?

The answer is yes it will run with a complete stuck turbo. You will come home . A QSB turbo will last 30,000 hrs. if:
Engine is installed correctly
Not overloaded
Intercooler serviced
Run @ or below 70% power
Routine oil changes
Engine never overheated

 

[Blissboat]

I'd agree and the easiest way to answer these questions is to walk down your local commercial dock and start asking questions when the guys aren't too busy. There is likely to be one or two common brands Their choices will be determined by operating cost, reliability and serviceability. Asking recreational guys introduces emotions and personal preferences. No offence to anyone but it's rare to find someone who spends $100k on engines in their pride and joy then admits it was a mistake.

Good advice!

 

[gsholz]

Turbos are very reliable as long as you keep salt water out of them. Too many installations do not provide sufficient dry riser height before injecting sea water into the exhaust. Many installation have a wet riser which is bound to leak salt water into the engine due to corrosion at some point. Something to check before buying.

The biggest maintenance headache in modern diesel engines are seawater cooled after/intercoolers. They require constant maintenance and replacement. E.g. CAT requires replacement every 6 years, removal and pressure testing every two years. If neglected, catastrophic engine damage ensues. Replacement can cost 10s of thousands. If given a choice, I'd prefer a jacket water cooled after/intercooler. Not very common but some larger CAT engines have them.

In my mind, the most reliable modern diesel engine would
- have dry risers for turbos with sea water injection on the downhill side
- have jacket water cooled after/intercooler
- reach WOT+ rpm fully loaded
- produce less than 60 hp/liter displacement
- be run more than 300 hours per year

 

[fgarriso]

Given your desires I would recommend a pair of CAT 3406-B motors. No electronics, purely machinal motors. HP 200 to 500 depending on how they are setup. AND, they run forever.

 

[dhays]

Thank you all.

I'm still in the learning phase of this exercise.

Seems that common rail has a better track record than I thought.

Turbocharged, intercooled diesels are a requirement in this size

The application is not a trawler, but rather a planing hull, express cruiser 40+ feet in length.

BEST !

RWS

Since I know nothing, I’ll jump in here.

The common rail engines are very reliable from what I’ve learned provided you provide them with clean fuel and clean electrical power.

I ended up replacing an engine due to my ignorance of the later. In short, keep your engine start battery pretty isolated from any outside interference and you will be fine.

My power requirements are a lot less than yours, but I’d sooner get rid of my turbo-charger than I would the electronically controlled engine.

Again, I know nothing and my experience is limited (outside of the small diesels in my sailboats) to the two Cummins 5.9L QSB engines that I’ve owned. Notice that is two engines that I’ve owned in my one single engine boat.

 

[bowball]

I’m looking at a boat with twin Cat 3208 turbos, 435 hp. It’s a semi displacement hull and low hour engines. Rarely run at anything close to higher rpm as not fuel efficient for the speed.

 

[Jeff F]

I too believe that most of the electronically run, common rail engines have proven themselves to be reliable.

Agreed. I'd go one step further and say that for high HP applications I'd have a strong prefence for computer control. Anecdotally I'd suggest that the worst generation of marine diesels in terms of longevity is the last of the mechanically controlled engines, when they were trying to wring more HP out of relatively small engines without robust monitoring and control.

 

[Comodave]

I’m looking at a boat with twin Cat 3208 turbos, 435 hp. It’s a semi displacement hull and low hour engines. Rarely run at anything close to higher rpm as not fuel efficient for the speed.

Make sure you get a good survey on them from a qualified Cat mechanic. 435HP is about the top power, if I remember correctly, that they pulled out of that engine. Depends on how they were run on how long they will last. In the NA version they just about last forever.

 

[bowball]

Make sure you get a good survey on them from a qualified Cat mechanic. 435HP is about the top power, if I remember correctly, that they pulled out of that engine. Depends on how they were run on how long they will last. In the NA version they just about last forever.

Thanks. I think they had a 450hp version too. Yes, they are getting surveyed and the same quality boatyard has maintained them their entire lives and speaks highly about them.

 

[DavidM]

For a 40' express cruiser that I wanted to run at 20 kts all day long I would choose a pair of 450 hp Cummins 6Cs, a totally mechanical engine of 8.3 liters.

You can repower a run down pair of these with an essentially new Cummins reman of the 6C.

But I agree with the other comments that common rail, electronic fuel injected engines are quite reliable. They are a bit smoother, quieter, and produce much less soot than their mechanical predecessors. Just look at a modern diesel car and compare it to one 20 years older.

David

 

[darkside]

The OPs Yanmar 6LPs are a wonderful engine based on a Toyota Landcruiser. I had two in my last boat.
The only thing I didn't like is the fuel shut off solenoid was normally closed. That means even though it is a mechanical injection, you still need power to keep it running.

but I’d sooner get rid of my turbo-charger than I would the electronically controlled engine.
Not sure there are any common rail engines without turbos?

Our NA specified Yanmar common rail 4LVs on our current build, but then we found no availability till February 2022. We swapped to the mechanical 4LH and I must say I am quite happy with that turn of events. The local supplier said he would have chosen the 4LH in the first place, if asked.

 

[Comodave]

For a 40' express cruiser that I wanted to run at 20 kts all day long I would choose a pair of 450 hp Cummins 6Cs, a totally mechanical engine of 8.3 liters.

You can repower a run down pair of these with an essentially new Cummins reman of the 6C.

But I agree with the other comments that common rail, electronic fuel injected engines are quite reliable. They are a bit smoother, quieter, and produce much less soot than their mechanical predecessors. Just look at a modern diesel car and compare it to one 20 years older.

David

We are getting 26+ mph at 2200RPM with our 6CTAs in our Formula 41PC. So far they have been great.

 

[Lepke]

Currently my Ford diesel PU is dead, again, because of a sensor. I be screwed if I was out to sea with a singe electronic controlled engine. I've got lots of stories about commercial fisherman and electronic controlled engines breaking down. When they're brand new, you got a few good years.

Turbos are reliable, but they burn more fuel. If you don't keep the oil reasonably clean, one of the first problems is restricted oil flow to the turbo bearings.

 

[ranger58sb]

I realize this forum is not all about express cruisers, however thats what best fits my needs.

Seriously thinking about moving up size-wize to a non pod drive express above 40' with mechanical diesels

In looking at the possibilities I'm going to start with the engines first to narrow the possible boat choices.

While I don't care about Tier I, II, II etc I'd prefer not to go prehistoric with a 2 stroke setup

I also want to avoid those power squeezed series that end up with a short life

Turbocharged, intercooled diesels are a requirement in this size

The application is not a trawler, but rather a planing hull, express cruiser 40+ feet in length.

We had Cummins 8.3CTAs (in-line 6 cylinder Diamond 450Cs) in our previous 42' convertible. They worked very well in that application, were relatively easy to service, I liked 'em.

I've read re-man versions are relatively cost-effective, if you find a boat you like with engines you don't like.

For your application, I'd now prefer the common rail QSC versions... but then I'm not you.

-Chris

 

[rslifkin]

Currently my Ford diesel PU is dead, again, because of a sensor. I be screwed if I was out to sea with a singe electronic controlled engine. I've got lots of stories about commercial fisherman and electronic controlled engines breaking down. When they're brand new, you got a few good years.

Turbos are reliable, but they burn more fuel. If you don't keep the oil reasonably clean, one of the first problems is restricted oil flow to the turbo bearings.

With diesels, if you compare a smaller turbo engine with a bigger naturally aspirated one, both making the same power, the turbo should be slightly more efficient.



As far as reliability goes, that's the difference between good electronics and bad. Some implementations are rock solid, some are finicky. And availability of good documentation and tools for diagnosis is critical too. It's hard to band-aid or fix a problem if you don't have enough information to figure out what's misbehaving.

 

[guy with a boat]

Thank you all.

I'm still in the learning phase of this exercise.

Seems that common rail has a better track record than I thought.

Turbocharged, intercooled diesels are a requirement in this size

The application is not a trawler, but rather a planing hull, express cruiser 40+ feet in length.

BEST !

RWS

It usually takes people longer to make that conversion, so congrats on a fast assessment. And welcome to the 21st century.

 

[mvweebles]

If you want to go fast, you need a high power to weight ratio and modern electronics to make an engine efficient. A friend's 2014 52 foot power cat makes close to 20 kts while burning around 38 gph through his 425 hp Cummins twins. Another guy I knew had an older 60 foot motoryacht with larger engines turbo/intercooler and burned over 60 gph to do 18 kts.

Pick your poison. But if you want to go fast, suggest leveraging modern technology vs throwing more diesel at the problem.

 

[darkside]

If you want to go fast, you need a high power to weight ratio and modern electronics to make an engine efficient. A friend's 2014 52 foot power cat makes close to 20 kts while burning around 38 gph through his 425 hp Cummins twins. Another guy I knew had an older 60 foot motoryacht with larger engines turbo/intercooler and burned over 60 gph to do 18 kts.

Pick your poison. But if you want to go fast, suggest leveraging modern technology vs throwing more diesel at the problem.

There is a bit more too the powercat to SD comparison that just power to weight.
That said we are expecting around 15gph at 20kn in our new 40' build. With mechanical injection engines.

However for an express cruiser and running mostly in local waters nothing at all wrong with common rail from the supplier with the best reputation in your area.