Marine diesel

[HPSimpson]

3412E 1015 BHP. finished weight around 6400 per engine. The Cummins (I think this is the one) KT38 dry was around 9000. It's not just the engines to consider but all of the associated systems that are proprietary to the Cat.

I think rebuilding current engines would be better choice considering the electronics's on newer Cat's with all there add on stuff there is a lot of weight involved. My engines have2500 hours and will need to be rebuilt this year.

 

[SnoKing]

I think rebuilding current engines would be better choice considering the electronics's on newer Cat's with all there add on stuff there is a lot of weight involved. My engines have 2500 hours and will need to be rebuilt this year.

2500 hours and need an overhaul? When we sold the 33 Bayliner after 19 years the two little Cummins had a little over that in hours and were "getting" broken in. Only thing I every did was water pump on one of them, raw water pumps regularly, start relays, and not much else.

 

[HPSimpson]

I was checking the engine hour-meters wow I guess wrong there 4654 hours been using oil somewhat spoke with dealer said your hour meters aren't working in some time hmm. I schedule for dropping off there in next couple of days

 

[BoeingDiesel]

2500 hours and need an overhaul? When we sold the 33 Bayliner after 19 years the two little Cummins had a little over that in hours and were "getting" broken in. Only thing I every did was water pump on one of them, raw water pumps regularly, start relays, and not much else.

Snoking, was that a blue water vessel, or Lake? 19 years is great but how many hours?

 

[EDankievitch]

2500 hours, 4500 hours? We call that a slow year. We would run our gen sets 28-30000 hours before even thinking about doing an overhaul.

 

[AH64ID]

2500 hours, 4500 hours? We call that a slow year. We would run our gen sets 28-30000 hours before even thinking about doing an overhaul.

Quite often gen sets are low on hp per engine size and marine engines are high. That alone has a major impact on rebuild time, as well as being a propulsion engine vs an aux engine.

 

[EDankievitch]

True.. Gen sets run at ether 1200 or 1800 rpm. All the time. Still that’s low hours for requiring an overhaul.

 

[SnoKing]

Snoking, was that a blue water vessel, or Lake? 19 years is great but how many hours?

I said a little over the 2500 hours noted.

 

[SnoKing]

Quite often gen sets are low on hp per engine size and marine engines are high. That alone has a major impact on rebuild time, as well as being a propulsion engine vs an aux engine.

Boats are going up hill 95 percent of the time. only in heavy seas does the engine(s) unload.

 

[AH64ID]

Boats are going up high 95 percent of the time. only in heavy seas does the engine(s) unload.

A lot depends on the boat and the engine duty cycle too.

Moat the bigger boats I’ve been around only run at high load a small percentage of the time.

 

[SnoKing]

A lot depends on the boat and the engine duty cycle too.

Moat the bigger boats I’ve been around only run at high load a small percentage of the time.

Corrected it to say up hill!

 

[AH64ID]

Correct it to say up hill!

True, but prop demand curves aren’t linear.

It’s rare for a marine motor to be at 100% load at less than rated rpms, unlike in a vehicle. Even then it’s not sustained unless the prop is pitched wrong.

 

[SnoKing]

True, but prop demand curves aren’t linear.

It’s rare for a marine motor to be at 100% load at less than rated rpms, unlike in a vehicle. Even then it’s not sustained unless the prop is pitched wrong.

View attachment 126895

Cummins rates their marine engines at max load for something like 5 hours out of 24 hour period. They can be operated at 85 percent continuous. My 4tb were rated to 2800 RPM and I ran them at max cruise of 2550 RPMs and about once a year ran them up to see that they would still turn 2800, which was usually just after have the bottom cleaned and fresh bottom paint. That said, they spent more hours at 1550-1600 which was 8 knots at 3 GPH combined for both running. With diesel furnace and higher cruising they averaged around 4 gal per hour over the 19 years of ownership.

 

[AH64ID]

Cummins rates their marine engines at max load for something like 5 hours out of 24 hour period. They can be operated at 85 percent continuous.

Cummins has more than 1 rating. Anywhere from continuous at rated rpm to 1:8 at rated rpm.

https://www.cummins.com/engines/marine-ratings

Cruise rpm is then based on rated rpm and also varies.

 

[JR]

Duty cycle and HP are directly related.

The higher the duty cycle the lower the HP.

 

[Ozymandias]

Excavators or Dozer go at least 20'000 hours before an overhaul.
We do 2200 hours a year with them - commercially.

If they would tell me that I need an annual engine overhaul- they could keep it.

 

[AH64ID]

Marine engine overhaul schedules are more like aircraft engine overhaul schedules. You often overhaul an engine that doesn’t need to to keep it from needing it when you’re at sea. Again, varies by use and rating.

I don’t know if the newer Cats still have the “Cat hour” meter, but it varies it’s time calculation based on rpms. IIRC the 3406C my dad had was 1:1 on hours ago 1600, below was slower and above was faster. That was a ~600 hp unit in his commercial fishing boat.

 

[EDankievitch]

Most American made diesels are rated 80-90% load 100% of the time. Engines built overseas (Europe) are rated at 50% load 100% of the time. Unless otherwise noted.

 

[SnoKing]

Excavators or Dozer go at least 20'000 hours before an overhaul.
We do 2200 hours a year with them - commercially.

If they would tell me that I need an annual engine overhaul- they could keep it.

Even the old Ford Lehman 6 cylinder marine diesels would go over 6,000 hours easily.

 

[BoeingDiesel]

Engine hours are a good barometer along with scheduled maintenance in terms of equipment reliability but it is by no means a guarantee. It's one thing to go on a local cruise and lose an engine, and the thinking person will most likely have a membership to an "Assist" service to be towed back to port but, those that venture out of that safety net are pretty much left to their own devices. So to me, which is the safer of the two; bet the 7300, or so, hundred hours on the twins is safe or increase the odds and rebuild the life source of the vessel that will get you and passengers back to port?
The ocean is just as unforgiving as the sky...and wise to expect the unexpected.
Just my $ .02.