Our Leopard 45 came from the factory equipped with two 4JH45 marine diesel engines. It's a Yanmar common rail 4-cylinder inline diesel, and like all engines it requires regular checks and routine servicing to help it in top shape.
In this quick guide I'm going to run you through what we think are the key things to know about basic maintenance for the Yanmar 4JH45 and Yanmar 4JH57 marine diesel motors, including the service intervals, tools we keep aboard and main parts you'll need for servicing.
Difference between the Yanmar 4JH45 and 4JH57
Why is this about the Yanmar 4JH45 and Yanmar 4JH57? It's because they both use the same engine block, with the key difference being the tune on the engine.
Configuration | Yanmar 4JH45 | Yanmar 4JH57 |
Cylinders | 4 cylinders | 4 cylinders |
Displacement | 2.190 L | 2.190 L |
Bore x stroke | 88 mm x 90 mm | 88 mm x 90 mm |
Alternator | 12V - 125A | 12V - 125A |
Electric starting | 12V - 1.4 kW | 12V - 1.4 kW |
Dry weight without gear | 220kg | 220kg |
Engine dimensions | 870 x 589 x 627 mm | 870 x 589 x 627 mm |
Max. output at crankshaft | 45 mhp@3000 rpm | 57 mhp@3000 rpm] |
If you refer to the Yanmar Service Manual: Marine Engines 4JH45, 4JH57, 4JH80, 4JH110, the servicing requirements for the 4JH45 and 4JH57 are the same too. In our opinion workshop manuals are one of the best sources of information for servicing specifications and if you're planning to do your own servicing it's a good idea to get yourself a copy.
Tuning the Yanmar Marine 4JH45 for higher output
While our blocks are Yanmar 4JH45's, they now do 60 HP with the addition of the Steinbauer Power Modules.
These modules improve your engine tuning by optimising the injector cycle, following the same principles as OEM manufacturer tuning. They're a proven technology that's been used in a range of applications for years, and are now installed on multiple catamarans.
Yanmar servicing intervals
The first servicing interval for our Yanmar marine diesel engines was the initial 50 hours service, which was done as part of the run-in period for the engine. After that each item on the routine list of maintenance has a set time interval it needs to be done at.
Every 250 hours or yearly whichever comes first
Every 500 hours or 2 years whichever comes first
Every 1000 hours or 4 years whichever comes first.
Since the intervals differ you'll need to look across all items when doing a service to see which tasks need to be done
.
At the 250 interval it's only 250 hour tasks
At the 500 interval it's the 500 hour and 250 hour tasks
At the 1000 interval it's the 1000 hour, 500 hour and 250 hour tasks
How to service your Yanmar diesel engines
To service your Yanmar engines it's important to ensure you know exactly what you're trying to achieve and how to get there. While a basic service is relativity easy to do, a small error or misunderstanding could cost you thousands in repairs. Education, attention to detail and having the service manual are the best way around this.
If you're still building your skills you may want to take a course or hire a Yanmar mechanic or experienced cruiser to provide 1:1 lessons on how to do it. Having the workshop manual for your engine is invaluable and YouTube tutorials or blogs can also be helpful.
What needs to be done depends on the service, so it's a good idea to work through each step carefully and methodically.
Tools and equipment
Starting with the basics, here are the general tools and equipment that you'll use and likely to already have aboard.
Cleaning solvent like isopropyl or methylated spirits
Various funnels for filing oil and diesel
Empty oil container to store old oil for proper disposal
Now for the things that are more specific to engine and sail drive servicing.
These tools do get used for other things around our boat aside from the engines and sail drives, including installing parts, servicing the generator and fixing random issues that pop up. If you have any questions about them be sure to leave a comment at the bottom of the blog.
Yanmar impeller puller
When you need to replace the salt water impeller your life will be easier if you buy a Yanmar impeller puller (129671-92110). While you might not need it every time you do a service, it's a one off purchase that's not overly expensive and can save you time and a possible headache.
Servicing spares to keep aboard
At each servicing interval there are specific parts that need to be checked and changed. You may not always be near a Yanmar dealer, so it's useful to have the spares aboard.
We have a 2021 Leopard 45 with two Yanmar 4JH45 motors. Based on the service manual we have, these are the parts that are needed to complete the periodic maintenance on the 4JH45 and 4JH57. Keep in mind that some tasks, like draining water and sediment from the fuel tank, need to be done but don't require specific parts other than fluids.
Initial 50 hour service |
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Every 250 hours or yearly |
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Every 500 hours or 2 years |
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Every 1000 hours or 4 years |
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The part numbers above are a guide as they can change or become discontinued. For example, diesel filter (129A00-55800) has been superseded by diesel filter (129A00-55810). Its always a good idea to look at your current filters as they should have a part number printed on them.
Fluids
When completing a service you'll also need to have the right fluids on hand. We keep enough for at least one service on the boat at all times, just in case.
Coolant
Antifreeze coolant
Engine oil
Check your manual to ensure you have enough of the right fluids to complete the service you need to do.
For the engine oil, there is a difference in what you should use depending on the temperature. Use SAE10W-30 between -20°C to 30°C, and SAE15W-40 between -15°C to 40°C.
In regard to coolant, always follow the manufacturers instructions and check the compatibility. Never mix different brands or coloured coolants, and if you have a hot water unit onboard that heats from the engine make sure you know how much coolant it holds as well as your engine in order to have the right amount aboard for servicing.
Yanmar OEM parts VS knock off parts
In my opinion it's generally worth avoiding using knock off parts because despite the initial savings there's the potential for it to cost more in damages or excessive wear over time, and possibly leave you stranded.
The only exception might be if you're considering replacing a part with a high spec'd alternative.
HDI Marine exhaust mixer elbows
The Yanmar exhaust mixer elbows has made of carbon steel. Owners have anecdotally reported that they corrode and crack, leaking from the welds. HDI Marine makes an alternative out of stainless steel that has a thicker flange and tube wall compared to the OEM and being made from 316 stainless steel its ability to withstand corrosion is ideal.
Summing it up
Every boat owner and sailor should be capable of doing their own periodic maintenance and basic troubleshooting, not just to save money but also to develop an understanding of how their engines work. It could be the thing that saves you if a serious situation arises in less than opportune circumstances, such as the engine cutting out during an ocean crossing or a no start situation during adverse weather.
Doing these basic tasks will help to bring you more confidence in your vessel and mechanical skills, perhaps giving you the push you need to cruise in more remote and beautiful places.
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