Cummins diesels

[billy breeden]

I am looking at several used 28' CC's. It seems like most pre 2004 have Cummins diesels. I've heard from two CC owners to stay away from Cummins because of problems and to look for boat with either Volvo or Yanmar. Any comments. Thanks

[Captain Spike]

It seems that whatever motors you have someone will tell you a horror story about them. I have Volvos which many people hate but they've been ok so far. I'm sure I'd be happy with Cummins or Yanmars as well so long as I could get them serviced nearby.

[hooker]

Everyone has their own opinion. I would only buy a boat with Cummins. I don't care for either yanmar or volvo.

The reason being:

Both yanmar and volvo diesels are very high RPM engines in the smaller packages (typically over 3500 RPM). They run great for a while but have a tendency to have problems after 1000 or so hours. These issues include smoking bad and loss of compression, poor idle, and hard to start. Remember, diesels have much higher compression ratios than gasoline engines and the harder they run, the more wear you get. Think of it this way, a yanmar or volvo will turn approximately 1000 times more a minute at cruising speed than a B block Cummins. Thats 60,000 more revolutions in one hour. Thats 60,000,000 more revolutions on a yanmar or volvo than you put on a Cummins B block in a 1000 hrs. That is a lot of extra wear on your cylinder sleeves and your piston rings. Both yanmar and Volvo (especially yanmar) pull alot of horsepower out of very small blocks. This is done by raising engine speed and raising engine compression by placing larger turbos on them. While this may be fine in a car (because they rarely run at 80 - 90% WOT), it can be a death sentence for boat engines. Lots of heat and friction take place at these continuous speeds, and I would expect a reduced serive life on any engine like this. If you want these things to last, be stringent with the maintenance.

In the past, (I do not know if yanmar is currently having these issues) Yanmar has had issues with using aluminum engine parts on their engines. They had major crevice corrosion and failure issues because of this. This is a black eye yanmar is still trying to get rid of.

Volvo has had several piston problems with smaller engines.

Again, these are issues that these two manufacturers have had in the past. I do not know of these being current issues (they may or may not be).

Now, before everyone starts bashing me for stating this:

I'm not saying you can't have a volvo or yanmar run forever without having major issues. I'm sure there are several people on this forum that have had a wonderful experience with them.

I am just stating what I have seen personally.

Cummins has been getting a bad rap on this page. The B Block has been around since the early 80's. It is a tried and true engine, and has a fairly clean service record.

However, if you are considering a used 28 with 4B 250's, you may want to get a service history and have a surveyor look at the engines. I think the 28's were a little sluggish with the 4B's and the previous owner may have run them hard, (above stated cruising RPM’s for extended periods), which may result is future issues. This however, is not a manufacturer problem, this is abuse.


G'Luck.

[Tswann]

Cummins

Cummins diesels are solid engines. As has been stated before, no matter what you buy make sure your local services point is capable. As far as earlier 28s with the 4Bs, search this site and read. In a nutshell:

The 4B is based on the B block, but is a 3.9L, 4cyl version. They have had issues with the fuel side (injectors, etc.) but these appear to be down to a dull roar. Fuel economy with the 4Bs is very good and performance is decent as well . . . This is a cousin to the 6B . . . The 6B is a rock solid, high population motor in both industrial and marine applications. My 28 had 6B 330s in her and was as reliable as they come and fast as &%$# . . .

Of course, the new QSBs and QSCs (32 and 35 power plants) have been very well received and have a solid track record. . . .

As far as rpm's go, since the days of the mechanically controlled fuels system have given way to common rail and ecm's, the old paradigms fall apart. Most of the common rail diesels are turning higher revs -- including Cummins -- of course with some higher than others . . . Hell the QSC600 is a 3000 rpm motor and the QSB480 is a 3400 rpm motor. This is not necessarily a bad thing. Mechanicals had to turn up to generate the horsepower, meet exhaust standards, compression, stroke . . . or . . . name your brand related issue. Now with the near car-like efficiency coming out common rails diesels, max/cruise rpm concern is less and less important because the ecm is controlling fuel, mixture etc at every step of the process. Load factor is the more appropriate measure for common rail(s). By way of example, the 35 we delivered with QSC600s routinely runs offshore turning 2400 (600 of the top) at efficient cruise at ~75% load; my old Detroit 892s at 650hp turned 1900 (~275 off the top) at 85%+ load . . .

[Bullish]

I echo Capt Spike...go with the manufacturer that has service in your area.

[Fish HARD]

660 hp or less...cummins makes the best engines available..that is not to say the others are bad...just that cummins makes the best...in a used boat..I would take the engines that were best cared for. A poorly maintained cummins is not as good as a well maintains whatever...but new...go cummins under 660 hp.....check out www.boatdiesel.com...join the $25 is a bargin