Diesel or hybrid engine on a boat – repowering considerations

Esper followtheboat installs a Beta 60 diesel engine in their boat


Welcome to the written version of our FTB Extra repowering video, in which we discuss in more detail Esper’s engine issues. After posting our initial issues up on social media we received an overwhelming level of support from around the world, from advice and ideas to links to spare parts and even a couple of engines. We really appreciate it, thank you to everyone who contributed.


We’ve taken on board all your suggestions and carefully considered each option. In this essay we break them down for you and look at repairing the engine, getting a recon engine, consider an electric/hybrid engine alternative and look at new diesel engines.

Note: this is an almost direct transcript of the original script for the video. As such some parts may read


To help put all this in context it’s important to examine our situation and our requirements whilst living aboard. This alone has an impact on a couple of options so let’s look at this first.

We’ve been living aboard Esper for ten years and we spend most of our time at anchor. We’ve crossed a number of seas and plan to do so again soon but right now we are cruising in between anchorages, reefs and rocks. Sometimes the weather can get hairy and in the past we’ve had to run our engine for hours at a time in order to get ourselves out of predicaments.

We have cruised and plan to cruise some more remote places. These remote places are sometimes a hundred miles or more from habitation. This has a significant impact on parts and availability.


Esper runs on 6v batteries in series (then parallel)

Esper runs on 6v batteries in series (then parallel)

We love our technology and run laptops, tablets, smartphones and have a number of items to charge throughout the day, not least cameras and drone batteries.

We watch movies, play music and have other creature comforts that means we consume a fair amount of amps over a 24 hour period.

So, we put high demands on our domestic battery bank and we do not day-sail between marinas. This means we are relying on the boat to keep our batteries topped up daily. We don’t return to the mainland to plug in to the grid.

It’s worth emphasising that, despite not wanting to admit it, we rely on our engine daily. Sailing is all very well but the engine is the heart of Esper and as important as the sails. Many of the places we have visited in the last ten years wouldn’t have been accessible without the engine.


To summarise, we have four options:

1. Recondition the head
2. Buy a reconditioned engine
3. Install a new electric or hybrid engine
4. Install a new diesel engine


A number of people recommended we recondition the head. Here’s some of the comments we received.

Michael Zietlo:

“In the US aluminium heads are repaired by heating up with a torch, grinding out the corroded spots, refilling the pits with a heli-arc welder and sanding it all smooth again”

Shaun Sim suggested that the head needs to be skimmed.

Tony Paul:

“Ali head – clean and weld it up. Far cheaper than new”

Steve Hock agreed and said:

“If it’s just a cracked head perhaps an expert aluminium welder could patch it”

And Tim Donaghey wrote:

“You’re in the place of cheap labour. Surely there is a back alley machine shop there who can weld and machine that head for some crazy low price.”

We discussed this option with our mechanic who had the same opinion as us. It may be possible to repair it but the corrosion that has set in to the aluminium head is pretty substantial. Take a look at the footage.

A workshop would have a hard time getting into the structure of the head without removing a large part of its integrity. In order to build up the corroded parts we’d first have to blast away the old corrosion, and that wouldn’t leave much left to work on.

Even if we were to go down this route how happy would we be installing a badly damaged part, reinstalling the engine and motoring away in the hope that this would keep us sweet for the next however many years we’ll continue to live aboard Esper? It’s an unknown quantity and not something we’re prepared to risk.


The advantages of finding another Perkins Prima M60 is that it’s a simple plug-and-play solution. Take the old engine out, put the recon in and away you go. No fitting issues or different parts to mess around with. No gear box ratios to match or problems with old imperial parts fitting new metric parts.

First we have to find a match. Fortunately a couple of viewers pointed us to an engine sitting in Dorset, UK, that was a match. The problem? We don’t know its history. We have no idea what condition the engine is in. And exactly how corroded is that head? By putting in a recon engine we a) inherit the same problems as our current engine and b) risk it breaking down due to some other age-related issue. Does it come with a warranty? What happens in the event of a breakdown?

A couple of people commented that fitting like for like is the obvious choice. But when we’re long and gone and Esper is still sailing, will she always need to be fitted with a recon Perkins Prima M60? These engines date from the 80s. They were fitted in the Maestro They are already obsolete and going down the recon route with an unknown engine is only putting off the inevitable. It could also open a new can of worms.

Of course to circumvent these issues we’d need to spend quite a bit of money on reconditioning an engine. A properly reconditioned engine is expensive. Here’s a great quote from Uncle Muir from our youtube channel:

“A rebuilt engine can mean many different things to different people. Mine means what isn’t replaced, block rods and crankshaft, are machined. Pistons can sometimes be oversized and the bore machined or stock size pistons (new) with new sleeves. New camshaft and followers, valves, springs, new or refurbished head, injection pump rebuilt also. That is a great expense if done correctly. Many try to shortcut the process, by the time you have a problem you may be far away or in a country where you will have no recourse.”

Another quote from Darren J2 on youtube:

“You may want to think long and hard about replacing with new. I had a gear box fail on the engine, then the engine died, that was re built, labour ate up most of the cost, then the starter went, more cost, then the fuel pump died, again more cost. I was fighting fire with the repairs. Had I foreseen what was going to happen, I could have had a brand new engine, gear box and ancillaries for considerably less money that stripping the old, replacing and rebuilding and then waiting for the next weakest link in the chain to break.”

Our friend Sam said something similar regarding this old Perkins. He claimed to have spent so much on repairing the engine he’d have been better off buying a new one.


We received this quote from Allen Helton on our youtube channel:

“I sail on one of these Hunter hybrids on the Chesapeake and it has a Volvo generator and whenever the batteries get to 20% it kicks in recharges the batteries for about an hour to hour and a half and then you can go a couple more hours before the generator has to kick in again but my understanding is that you could do that indefinitely as long as you have fuel so the only difference is that while the engine would run constantly on a standard diesel, on a hybrid for extended motor cruising the generator would only be on half of the time. Also when the motor is not on, the water turning over the prop turns the electric motor on the boat into a generator to charge the batteries Also while the generator is on it powers the motor if it’s running and charges the batteries at the same time.
In general, electric motors with only one moving part are extremely durable, of course you would still be dependent on the diesel generator for rapid recharging, so a diesel would still be the weak link in the chain. However if you did lose your generator, wind, solar and the prop generator could at least give you enough electricity to maneuver into a slip if your generator did go.”

One of the more controversial options is an electric engine, or a hybrid. It’s something we’ve looked into and assessed.

Firstly let’s just quickly look at what an electric/hybrid engine offers. They’re quiet, small, have great torque and run off either lithium batteries that are small, light, fast to charge, or thin plate pure lead batteries (variant of AGMs) and can be discharged down to 15% of their charge. They’re often sold as the green option but for us this is misleading since the way in which lithium is mined isn’t exactly green.

We also looked at hybrid engines. A serial hybrid system uses a large electric engine to cope with most of the propulsion and a large generator to recharge, whereas a parallel system uses a diesel engine to cope with heavier demands and reverts back to a smaller electric engine to manage the smaller maneuvers.

Serial hybrid engine

Parallel hybrid engine

Practical Boat Owner Diesel Hybrid EngineThere’s an extremely comprehensive report in Practical Boat Owner magazine written by boat maintenance guru Nigel Calder who spent a considerable amount of time examining the efficiency of these systems. It’s pretty technical so without going into too much detail he concludes by saying that the main issue is regeneration of energy whilst at sea – essentially wind and solar. In demanding situations, or rather situations where you are moving faster than slow-speed maneuvering in a marina, the energy required for propulsion is considerable. If relying on batteries you’d rapidly deplete them so in the serial hybrid set-up the generator would have to kick in – making the system less efficient than a standard diesel engine. The key to an efficient hybrid system is therefore the battery set-up. In Calder’s tests he claimed to charge 4 days worth of domestic power in 15 minutes through the generator, but the set-up costs put this way outside of our budget. He states that there are design compromises to the generator that would make it prohibitively expensive in the real world.

For us there are some major issues with the electric engine option. In no particular order we’ll look at each of these in turn:


1. The range
Our biggest concern is the range an electric engine can supply. In one case study where a boat owner installed a 7kw system the range is up to 20 miles at three knots, or ten miles at 5 knots. This is fine for a bit of small coastal hopping or sailing on a lake, but we cover a lot of miles. Take, for example, Jamie’s 90 mile solo sail covered in a recent followtheboat episode. The batteries would be on constant charge. How is this achieved? By installing a diesel generator.

2. The cost
In order to match the battery capacity required to not only power the engine but supply us with our high-demand domestic requirements we are looking at a new engine, a large bank of fast-charging batteries and a generator to charge them all. There is no cost advantage. In fact we’d end up outlaying a lot more.

3. Parts and availability
Electric engines require parts that are not yet readily available. When the brushes go on the engine, can I expect to find replacement parts off the west coast of Indonesia? When the control box between the engine and the batteries goes, can I find a replacement whilst anchored off an island in the Maldives?

We applaud those people out there experimenting with electric engines and hybrids. Sailing Uma. If we were building our boat from scratch with no budgetary constraints I think we’d look into this in more detail. Sadly our needs, requirements and budgetary constraints outweigh what is currently available. As permanent liveaboards living off the grid and visiting remote places we don’t feel a hybrid is is a sensible option at the moment. We are positive, however, that this is the marine engine of the future. The idea of being able to maneuver and motor quietly is an attractive feature.


Esper followtheboat installs a Beta 60 diesel engine in their boat

We opted for a Beta 60

Esper, and her engine, are approaching thirty years old. She’s traveled from the UK to Thailand via some difficult passages and the engine has clocked up many thousands of hours during that time. The thing is, we’re hoping to sail her for another thirty years, or until we drop, whichever comes first, and we need an engine that is going to see us through more difficult passages for many years to come.

A new engine comes with a number of warranties, not just those written on paper. We’re buying peace-of-mind. It should run trouble-free for many years, providing we look after it and service her properly. We’ll configure her to our specification and we’ll get to know her intimately.

A diesel engine is the obvious choice for the following reasons:


1. Established technology
Diesel engines have been around a long time and are established technology. They’re a known quantity

2. Easy to maintain and repair
Perhaps our biggest concern was what happens when something goes wrong. A simple diesel engine is easy to fix. Take, for example, our current situation. Any issues with an electric motor or specialist batteries would be difficult to deal with in the north of Phuket, Thailand. Importing is expensive.

3. Cheap
Despite the outlay, the cost of a diesel engine and the fuel it consumes is relatively low in the long run. Parts are also cheap providing the engine is made from off-the-shelf components.

4. Longevity
A diesel engine, if maintained properly, should last 30 years or more.


Our assessment of the repowering project depended on our electrical consumption concerns and the ease of maintenance. As heavy consumers of battery-powered products a cheap and reliable charging solution was of paramount importance.

The sailing range we encompass, which takes us off-shore and to remote places, also played an important part in our considerations. Finding parts and services for a simple diesel, naturally aspirated engine is a concern.

We love the idea of hybrids and believe they will play a much larger role in the future of cruising. Our budget played a big part in crossing this option off the list. So, too, does the concern for additional charging components (from generator and alternative battery installation).

The aim of this essay, along with the accompanying video, was never to offer a recommendation. With the current availability of parts and the early developmental stages of hybrids, however, we felt that a traditional, marinised diesel was the way to go for us currently.


Beta Marine: http://www.betamarine.co.uk/

Elco electric engines: http://www.elcomotoryachts.com/

Exide: http://www.exide.com/

Practical Boat Owner article: http://marinedirectory.ybw.com/reprints/results_related.jsp?tem=ybw&id=89141

Article on LiFePO4 batteries: http://www.pbase.com/mainecruising/lifepo4_on_boats&page=1

How you can support followtheboat: https://www.patreon.com/followtheboat


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2 Comments on “Diesel or hybrid engine on a boat – repowering considerations”

  1. How about recycling the alternator from the Perkins and the prop from the outboard? Simply epoxy a two to three foot rod into the hub of the prop, epoxy or weld a link of chain to the free end of the rod, snap a sturdy length of rope to the chain link and toss the prop overboard while sailing. The prop and rope will spin the alternator and provide another source of 12v providing the alternator spins the right way around. A simple method of reversing the spin direction may have to implemented. I know you are up to the task, Jamie. (This might be the subject of an extra blog.) AND I FOLLOW THE BOAT!!!!!!!!

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