Checking Engine Drive Belts and Pulleys

Diesel engines have a great reputation for incredible longevity, yet most recreational marine diesels fail well before they should. The two primary killers are 1) overload (discussed at Diesel Engine Overload and Tony Athens’ Engine Life vs. Engine Loading) and 2) poor maintenance & operating conditions. Both are easy to avoid with a bit of knowledge, particularly overload.


On the second big killer, poor maintenance and operating conditions, it’s clear that a high quality scheduled maintenance program is a good investment. Beyond that I’ve adopted two simple techniques that have really paid off for me: 1) spend a bit of time with the engines, and 2) know your specific engine’s weaknesses and failure modes.


For the first one, just spend time in the engine room. If you know what it should smell like down there, what sounds are normal, and you frequently visually inspect, it’s amazing what you will find before it becomes a dangerous problem. From spending just 30 seconds in the engine room each day, I’ve found a variety of problems that could have become more serious. For example, the support bracket for the engine-coolant header tank broke once. At that point, the header tank was hanging from the hoses. If the hoses break or abrade, there is a good chance the engines will overheat, one of the quickest ways to shorten diesel engine life. Spotting this early means it’s a complete non-issue. In another engine room sniff, I smelled diesel. It never smells like diesel down there, so I looked more closely and found a fuel-tank vent-hose clamp had rusted through. If you keep the engine room clean and well lit, any leak from any component can be seen quickly. I’ve had several raw water pump failures, each of which was proceeded with a raw water leak at the pump seal (Changing the Raw Water Pump). Catching these problems early keeps the engines safe.


The second of my two simple techniques is to know your engines and their failure modes. This one also is incredibly easy. Find a forum where your engines are broadly discussed. For Cummins Marine, Boat Diesel is an excellent resource. From reading about your engines, you’ll start to learn the weak points and where a little extra attention is well worth paying. In the Cummins B-Series engines, I keep a close eye on the raw water pump and engine accessory-drive belt-idler pulley. Both fail more frequently than they should and warrant a bit more attention. I just posted a short article on checking the engine accessory drive belt and idler pulley: Belts and Idler Pulley.


James Hamilton


If your comment doesn't show up right away, send us email and we'll dredge it out of the spam filter.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.