How to install a common rail diesel engine on a boat

Tired of battling the tides, John Willis installs a new common rail diesel engine in his pilothouse yacht

The end of the evening turned into night as Reinette apple battled the opposing tides off the windward Corbi̬re, his old Yanmar battling the elements like a featherweight pushing Mike Tyson. To be fair with the engine, Reinette apple Рalthough she is slender Рweighs 8 tons of comfort, so it took me an age before I could tear down and let the sails take the strain.

Sure, Reinette apple is a sailboat, but sometimes I’m completely wrong and the formidable tides of the Channel Islands turn against me, or I just want to go home for the Southampton game. I’m not a sailing purist and an extra knot from Jersey to Guernsey saves me a good chunk of an hour; do those 100 miles and it’s over 3 hours.

As I was once again seated admiring a near-static seascape, I decided that it was not unreasonable to want my boat to sail and power to its potential; maybe it’s age related, but i dreamed of a Reinette apple capable of improving 6 knots at 70% max rpm and picking up hull speed for the first time in 24 years, a dream I could finally afford thanks to a timely home sale.

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But nightmares followed. What brand of engine? “Common rail” or “conventional”? On the internet there are millions of arguments in favor of most engines, except common rail diesel engines for small yachts.

Scary research

I poured my agony into comparison spreadsheets and it led to a quick decision because I hate faffages; a decision which brought another wave of doubt as I had chosen a £ 8,000 Yanmar 3JH 40CR. Yes, it’s a common rail diesel engine (the smallest in the world) but the internet is full of terrible warnings.

However, like the first hint of a sea breeze, I feel the tide of opinion turning to embrace this not-so-new technology, an embrace I happily made because I can no longer mend a mechanical thing than fix a defect. on an electronic control unit – but I can do the basic maintenance required by any diesel.


The original engine struggled to keep Reinette apple move against the tide

Then there is the environmental issue. Although well maintained, my old Yanmar stubbornly cried his vital fluids, straining every 950cc to provide forward movement, his obvious sweaty works from the smoky gray transom and a thick beard of pollution along the line. of water, which I conscientiously scoured from time to time. By comparison, this common rail diesel engine is cleaner, slightly more economical and comfortably produces more torque than a well-known “conventional” competitor.

I calculated the cost of the project and then doubled it by entrusting it to an expert. The total engine installation would later amount to £ 12,000; an old boat like Reinette apple has tight spaces requiring custom installation, not to mention the inevitable discovery of things to be fixed.

Dismantling the old engine

Getting the old 130kg motor out was easy enough and it was a shock how tidy it was, as it sat sadly in the workshop, weeping softly. By comparison, the new 1642cc 192kg beast looked huge, so I rushed to measure the companionway again to decide it was impossible! But the engineer disagreed with calm and who am I to argue, so I snuck in to don coveralls and clean the engine bay.


Old broken down engine and time to tidy up.

The new engine had to be mounted further forward, so a longer propeller shaft was required, which could not be installed with the engine in situ due to the location of the rudder.

A larger propeller was impossible, but Darglow engineers looked into the problem and sent in a new hub cartridge to change the pitch of the 16 inch feathering propeller blades – it was perfect.

Significant “surgery” was required to create additional space; no surprise but scary all the same. After some thought, the engineer deduced a way to open the engine compartment.


Longer driveshaft was needed

He lowered a non-structural longitudinal subfloor bulkhead next to the engine and cut a cutout in the transverse subfloor bulkhead just ahead.

9mm thick stainless steel flat bars were then machined to fit over the top of the mounts to accommodate the new engine mounts.

Bigger inside, bigger outside

The larger engine required more cooling water, which required a larger opening in the keel and a new sea inlet – a great opportunity to remove the old raw water strainer from the bottom of the bilge and place the replacement Vetus unit next to the engine.


New Vetus lock

Bigger in bigger, so a larger diameter tailpipe was fitted as the money meter inexorably kicked in. Somehow, a Vetus water lock was stuck under the cockpit and a bigger exhaust pipe went up high in the stern and down to a new, larger hull fitting.

An anti-siphon unit has been installed inside the wheelhouse locker, with a drain in the cockpit.

One thing a common rail diesel engine must have is meticulously clean fuel. Having encountered a diesel bug before, I had a Racor fuel polishing system installed that can polish a full tank three times per hour, with or without the engine running.


Racor gasoline polisher

A small electric fuel pump was reused to recharge the Racor engine pre-filter (not really necessary) after changing its filter, and we added a water alarm.

Unexpected problems

Unexpected problems have arisen. For example, to accommodate the fuel line from the fuel polisher, a new stainless steel fuel tank top plate with additional fittings was made and, in the process, the original fuel filler pipe (which was made of the wrong material) broke, as did the hose breather.

Naturally, the joinery had to be dismantled to replace these pipes and the bill was getting higher and higher. With everything open it was possible to remove some old redundant wiring and tidy up the area under the wheelhouse floor.


New propeller pitch cassette

I also had the internal throttle and unused cables removed, leaving only the hydraulic internal steering. A Yanmar C-35 engine control panel was installed as well as a new fuel gauge. I was fed up with the old gauge used to say ‘Full’ before suddenly diving to ‘Empty’, so a vertical lift float sending unit was installed to replace the old swingarm unit.

With the end in sight, we turned to making a new engine cover and came up with a simple design of sliding panels in marine pleats, installed between the captain’s seat on the port side and the galley on the starboard side.

Insulated with soundproof material and finished in veneer and Treadmaster, it replaces the old heavy motor housing and makes a great seat for kitchen work.


Motor housing doubles as a convenient seat for kitchen work

Common Rail Diesel Engine Costs Rise

Stunned by spiraling costs, madness overcame me; for a penny for a pound, so I sanctioned other projects such as installing a Raymarine sonar, re-glazing the main hatches and replacing the old cooker with a simple hob and grill, which opened up a large area below.

You can never have too much storage and the second one suggested it was perfect for a storage box to hold my little travel luxuries like Marmite, Gentleman’s Relish, Ketchup, and boxes of smelly fish stuff.

Even the best engineers and carpenters aren’t usually known for their housekeeping, and that, added to my hoarding habits, meant the cabin was now filled with a huge bonfire of dismembered furniture and newly redundant pieces.


Reinette applehelm station

It wasn’t bad as several long-forgotten items revealed themselves in various strange places.

The lockdown took place on the scheduled launch date, so it wasn’t until several weeks later, on a cold March day, that Reinette apple slipped gracefully into the water and the engine fired for the first time.

At sea in calm conditions, she bounded quietly towards St Martin’s Point with hull speed on the clock and the smile of a Cheshire cat on the skipper’s face.


Relaunch time for Reinette apple with a new common rail diesel equipped

Reinette applethe hull speed is just over 7 knots, and she now settles comfortably at around 6.75 knots with 70% throttle in acceptable conditions, 1.5 knots faster than before, which should save over 2.5 hours on a cross channel trip to Weymouth – although I prefer to sail it.

The whole project cost £ 20,000 but hopefully I’ll never have to look at the Corbière for two hours again… as much as I love the place.

About the Author

John Willis, 66 ¼, is an ex-soldier, businessman and thrifty. He has traveled more than 20,000 miles, mostly solo, on small boats sailing north to Shetland and south to the Azores. He is the current guardian of Reinette apple, a Frances 34 Pilothouse, and her mantra is that there’s never a better time to go – so go ahead and do it.

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This feature first appeared in the November 2021 edition of Convenient boat owner. For more great items like this including DIY crafts, money saving tips, great boat projects, expert advice, and ways to improve your boat’s performance, subscribe to a subscription to the UK’s best-selling boating magazine.

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