Electric Motor now or later?

In Zero Fossil fuel sailing and other posts we have written about a long term goal to replace the diesel inboard engine in Vida with an electric motor. That with a battery bank charged from renewable energy (regen from the propeller when sailing plus solar and wind electric generation).

However, the Yanmar 3JH5E engine is only a few years old with under 400 hours of use. So it seemed to make economic sense for us (one aspect of our goal of sustainable sailing is that it should be financially sustainable for us) to wait for a few years while minimising the use of the engine.

At the moment we seem to be changing our minds. As we have been getting to grips with other jobs we have been discovering more about the engine installation, and it hasn’t been good news.

Diesel tanks and supply

We have realised that when the engine was replaced the fuel tanks and supply pipes were left as they had been. So we have 42 year old stainless steel tanks, fuel pipes and taps. We didn’t know much about diesel systems but the more we learn the more this worries us.

Whilst, this would have been a first class installation when new (which is why it has lasted 42 years) it doesn’t meet the standards that we are reading about in our boat maintenance books. So there is no access hatch to allow the tanks to be inspected or cleaned. There seems to be no way to get sludge out of the tanks (or even discover how much is there). There doesn’t seem to be a sump to collect sludge either and the supply to the engine appears to be coming from low down in the tank (on modern tanks the fitting would be on top with a pipe extending down inside the tank, this makes it less likely that it will pull sludge from the tank and allows it to be taken off to clean it).

We hadn’t realised that diesel engines have a fuel return to the tank, we have found this on the port tank (inside the cockpit locker) but not on the starboard tank alongside the corridor to the aft cabin.

The fuel pipes are really confusing, there are many more of them than we can make sense of, with about 9 taps on them – none labelled and many of which we don’t know the purpose of. Sadly, quite a few look quite corroded but access is very difficult. We have found a “transparent” (well once transparent more accurately) pipe in the engine compartment which serves as a fuel gauge, we just can’t “read” it.

We knew one of the fuel filters was leaking, but they are surrounded by a mass of pipes and taps, possibly so that you can choose one or other fuel filter.

This leaves us very concerned. Fuel contamination is a really common source of problems for boat diesel engines. Modern diesel often contains a proportion of bio-diesel, if you don’t have enough additives in the tank this “grows” sludge that can clog pipes and filters very quickly. That is especially a problem when rough seas stir up sludge (often just when you want the engine the most) and where supplies around the world can be of very variable quality.

So we have a very old fuel system we don’t understand, that is going to be very difficult to clean out and which may need multiple, inaccessible parts servicing or replacing.


Again when the new engine was fitted the “drive train” appears to have not been updated. Some parts of this we know need replacing (cutlass bearing = which is the tube like bearing that the propeller shaft comes into the boat through) or servicing (stuffing box – what stops water coming into the boat through the hole for the propeller shaft).

What we have now discovered is that the coupling to the gearbox on the propeller end looks original and is rusty. From what we have read and seen from others is that this means it is highly unlikely that we will be able to successfully remove this. Without removing this we can’t slide the propeller shaft out of the boat (needed to replace the cutlass bearing). That would leave the options of somehow cutting the propeller shaft and replacing it or lifting the engine out of the way to pull the propeller shaft out into the boat.

Bilge access

It has taken us a while but we have now found where the lowest part of the bilge is (this is where any water inside the boat will naturally drain to). Very inconveniently, it is under the engine. There is a glass fibre “tray” (sort of like a false bottom) under the engine so that oil leaks etc don’t mix with water in the bilge. So there is one hose for the old manual bilge pump going down by the side of the propeller shaft into the bilge behind the engine tray.

For safety reasons we want to have both a manual bilge pump and an automatic electric one (these just were not available 42 years ago). If nothing else this buys you time to look for and plug a leak while the pump stops you sinking. Fitting these with the engine in place is going to be very tricky (because we need to fit 2 hoses and a water level sensor into a tiny space we can’t really reach).



Try to keep the existing engine going for a year or two with minimal expense. That would mean this year:

Replace the seackcock for the cooling water inlet; Change oil filters; repack the stuffing box; trace and label all the fuel pipes and taps; siphon out the diesel fuel and try to flush the tanks (access using only the deck fuel filler); reconnect old 12volt starter battery (in a new battery box); change the oil; create a new sound proof partition to the cockpit locker (old one was part of the old battery box and was incomplete).

It would mean not adding an electric pump at present and not changing the cutlass bearing.

Cautious to improve reliability

This would be the minimal plus changing the cutlass bearing and fully servicing the fuel supply (new transparent hose for fuel gauge, adding a water filter, checking all pipes and replacing the most corroded).

Go electric

Accept that this is where we want to be long term and rather than spend any money on the diesel engine systems, take them out and replace with an electric motor. This is where my heart lies, it will allow us to fix all the problems and gain some extra benefits (the space taken by the fuel tanks being a significant one). But it is expensive and a lot of work.

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