When you can incrementally introduce heat and friction through use, your marine engine parts will begin to wear against each other to conform to the shape that will provide the tightest fitting seal essential for achieving optimal, lasting performance.

Do you have to do a new diesel engine break-in? Well, no you technically don’t. However, it can be incredibly shortsighted and careless not to. Taking the appropriate steps to prepare your equipment for heavy-duty use will reduce your chance of leaking fuel and pressurized gas for increased fuel, economy, power and efficiency.

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How to Break In a Diesel Engine

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Your new or rebuilt engine break-in procedure is a relatively simple process and can be accomplished quite easily. While the steps in most cases are consistent, there may be variations in your break-in procedures depending on your make and model, and whether or not you’re doing a rebuilt engine break-in. When breaking in a diesel engine, you should always consult the factory-recommended specifications found in your boat’s operating manual.

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Break-In Procedures

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The ideal method for breaking in an outboard or inboard diesel engine is by running it on a dynamometer in a controlled environment. However, it’s also easily accomplished when already installed in your boat if you lack access to the proper equipment.

Before you start your new diesel engine break-in, you should always start by examining the basics of your marine engine. Look for twisted engine mounts and loose bolts. You should also ensure your wire runs look correct, your drive belt is tight, and the appropriate seacocks are open. Then, you can start your engine and let it idle for five minutes to ensure you’ve got cooling water flow at the exhaust port and full shift control. Check to make sure your oil pressure is stabilized and there is no leaking.

Following your initial startup checks, you can begin breaking in a diesel engine by first lightly operating it for either a few hours or 100 to 150 miles. It’s important to note that during this time, you should avoid prolonged idling as much as possible. You’re only looking to create a small amount of initial heat, so be sure to keep your marine engine in the highest possible gear and run it at no more than 75% to 80% of the power rating. Continue to ramp up the RPMs and load on the engine progressively – not at full tilt. You’ll want to increase the demand put on the engine until you’ve reached 15 hours or 1,000 miles.

If you’re wondering how to break in a rebuilt engine, the break-in procedure remains largely the same, except you’ll want to push it about 1,500 miles for better wear on the parts.

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Helpful Tips for How to Break In a Diesel Engine

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While running your engine break-in procedure, there are a few helpful tips you’ll want to keep in mind:

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