Engine Life

Engine Life

I’ve seen more than my share of premature failures of Cummins B’s and C’s long before they should have occurred.. Many of these failures have been “unexplained” in the “warranty world” but this is usually due to keeping public relations at an acceptable level.. In actuality, the failures could have been traced to the following (put in an order of relevance from my experience):
1. Over propping – plain and simple. There seems to be a perception in this industry that if an engine is rated 2800 RPM and the manufacturer says that you can cruise at 200 RPM less (2600,) that “200 off the top” still applies if the boat can only reach 2710 RPM on one engine and 2735 on the other engine in a very typical twin engine boat. The “little bit” (actuality a lot) of over propping puts the engine WAY outside of it designed application/designed power curve. Take a 3800 RPM rated engine; it typically is even more sensitive to being over propped.

On this same subject, I’m still waiting to see builders, installers, and operators (all equally guilty, although I feel the root of this problem starts with the builders of new boats,) really understand the concept of having a boat propped to its “working weight” and “working bottom” and NOT the unrealistic sea trial condition of the boat. Just filling the bait tank, fuel tank, and/or water tank can easily put the engine at serious risk as it now operates in a varying degree of light to serious overload.

I fielded a call from a guy who just had his boat repowered w/ a set of new 450 Diamonds.. I had done a “kind of bid” on this repower myself about a year ago and knew the boat well. A heavy 38 footer with big swing loads (bait tanks, fuel and gear) of 6000 + + lbs. He’s wondering about black smoke, and why he can’t get over 2450/2550 RPM (or so) when he’s loaded up to go fishing. By the way, he loves his 450’s and their performance, I just hope he follows my advice and gets his boat propped correctly and installs boost gauges to actually measure his load, BEFORE he’s done the initial damage.

2. Lousy operating environment – I put this ahead of poor maintenance because I’ve seen so many problems with engines due to salt water dripping on the motor or being sprayed or sucked into the intake. A lot of engines that I’ve seen failures on have had good maintenance as far as oil changes, etc., but the owners were oblivious to the tell-tale signs of salt water damage. I cannot stress enough that a clean, dry engine room with good ventilation is one of the most important parts of engine longevity. And, realize that very high performance diesels are even less tolerant of salt water ingestion.

3. The nut behind the wheel scenario – This is pretty self-explanatory and probably covers items 1. and 2. along with lousy maintenance and general care of the boat. This is a guy that “operates on the edge” of everything, and I see this a lot with operators w/ “Detroit Mentality”. Sorry Detroit fans, but I deal with a lot of commercial fisherman.

4. Installation related failures – Poor exhaust design leading to water intrusion is the single worst culprit that I’ve seen (see the Cat/Mainship thread.) Sailboats are notorious for this because the engines are typically at or below water line level. Here is where good solid engineering, along with experience, will make or break an engine. Exhaust leaks and high restriction can also lead to shorter engine life. There are many things to do with installation related failures such as ( fill this in Karl)…., I could go on and on.

5. Just plain old poor maintenance – Along with not doing the scheduled stuff (oil changes, valve adjustments, filters, etc) there are many operators who wait until a simple thing fails which leads to catastrophic damage.. A typical example is: Belts and coolant hose failures that happen at high cruise HP levels when things are really churning and you lose cooling “all of a sudden”.. The lighter diesels that drive this market do not have much reserve to tolerate these kinds of over heats.. You see blown head gaskets, cracked manifolds, cracked turbos and heads. These lighter wt engines that put out in excess of 1 HP for every 4 lbs of cast iron, just don’t have the extra beef like the old Detroits did (do) that may only develop 200 HP and weight 3000 + lbs.

I’ve seen alternator bearing failures lead to a rebuild of the engine as, when the bearing finally went, it took the belt and cooling circuit with it… The early design of the idler pulley on the front of the B Cummins had enough warranty failure rates to where the engineers re-designed the support of that pulley to add strength. Usually, bearing failures like these can be caught by sharp operators if schooled correctly by a good mechanic.. Take your belt off once a year or so and free spin these things and “listen and feel”.

6. Fuel system failures – These are close to “ALL preventable” from my perspective as an operator should see signs of trouble before its too late.. Most modern diesels have very high fuel flow rates and need not only much higher capacity filters, but higher quality filtration than diesels with fuel systems designed 20+ years ago.

Gosh, it’s getting late again and who knows how many more horror stories are out there from operators who have had such bad luck.. Of course, I don’t believe that (bad luck,) especially in this case, Mike, as I’ve got a sneaking suspicion that your bad experience(s) can be traced to something I’ve mentioned above.. Although I don’t sell Green engines, I’ve seen too many of the 60’s & 70’s run for 1000’s of hours and have happy owners to boot. The 63 Volvo has a lot of good history behind it and you need to take a serious account of your problems, try to put them down in a logical format and let Karl help find out what’s the matter.