Engine Work 2

Here is the second of a few non-Finesse specific posts but as a practical boat owner who does all their own repairs and maintenance I thought I would share on the blog..


On re-commissioning Enfys last season we discovered that the engine's alternator was not charging. A quick check of engine wiring loom and controls revealed that the alternator was receiving its excitation voltage but the output was dead.

N-D Alternator - Loose wire protruding from rear cover is a direct connection to one phase
of the AC windings and provides a pulse-train for the tachometer

I removed the alternator and took it home.  Usefully (not) the engine mariniser had sprayed paint all over the data plate making it illegible so it took a bit of detective work to find out that the alternator is a 'Nippon-Denso' with an output of 40A.  It was the internal voltage regulator that had failed - there was no visible damage or corrosion - it just decided to stop working after the winter lay-up. I must say how poorly and cheaply-made this machine is; not really suitable for the marine environment, in my opinion. Pricing up a replacement showed that it was not cheap to buy though... despite being the same as used on plant-based Kubota engines.

The regulator is the module on the left with a heatsink on its back.

Regulator assembly

After a couple of attempts a correct replacement regulator was sourced from an auto-electrical parts supplier and the machine was re-assembled and tested on the bench by spinning it with my electric drill. Whilst in the vice I blew copious amounts of black dust, from the 'V' belt, out of the machine's internals.

Connected up for test. My 'test' battery is a little tired.

Engine Work 1

Not unique to a Finesse but Enfys' engine is a 20hp Beta based on a 3-Cyl Kubota industrial engine.  Sometime prior to our purchase of the yacht there had been a water leak at the raw water outlet at the back of the engine probably caused by a poorly-fitted hose. This would have been typical of the shoddy standard of this particular engine installation that was noticeable elsewhere too.
The exhaust outlet was heavily corroded and I noticed a crack had appeared in it - time for replacement.

Finally got the old elbow off leaving three broken bolts in situ.


The fixing bolts were M8 mild steel and might as well have been made of chocolate as three of them sheared off as soon as I put the spanner onto them. After a bit of sawing and hacking I got the elbow off.

Remains of the elbow after my hacksaw had done its stuff

The reason why the corrosion was so bad soon became apparent; the heat exchanger and elbow are made of aluminium alloy and were jointed by a copper-faced gasket.. doh!

Copper faced gasket had been used on original assembly

I had to remove the whole heat exchanger from the engine and put it on the bench to tackle the removal of the broken bolts.  It was assumed that these would need to be drilled out and the trashed holes would need to be 'Helicoiled', however, to my surprise I got all four out and cleaned up the blind holes with a tap. A new elbow and joint gasket were sourced from Beta Marine - the new gasket was fibre. Instead of using new bolts I 'Locktighted' M8 threaded studs into the holes in the casting and bolted it up with nuts and washers - hopefully making it easier to remove next time.

Studs fitted once mating face had been cleaned up

New elbow fitted to heat exchanger

Next post will cover another corroded pipe and fittings on this engine...