Westerly GK24 and a Yanmar 1GM7

Late in 2002, I began to notice that the engine had three problems:

It was getting sluggish on starting, it needed the starter button pressed for about five seconds after the engine began to fire.

It tended to die when a flat battery was connected to the alternator just after the engine started.

It also produced black smoke when the engine was asked to push the hull at more than about 4 knots. Some of that may be down to fouling on the hull.

A few worse instances had turned out to be pieces of string around the prop, the rope cutter disc had obviously been working. Often hitting astern and ahead would clear it.
I had spent a lot of time tweaking the governor, and when the engine was set so that it would tick over when the engine sta,rted, from cold , the smoke was worse and vice versa.
In the past we had reground the valves, had the injector serviced several times, checked that the piston still reached 0.7mm from the piston head and generally checked the engine over and over
According to the invoices we have, th engine reaches its 20th birthday this year, and I decided to talk to Marine Power at Bursledon about it.

I finally tracked down Pete and he told me to strip the alternator, starter and gearbox from the engine "and then you can pick it up by yourself".

In previous years I had bought a Yanmar GM service manual and I spent several evenings studying it to make sure I knew the most efficient places to disconnect pipes and wiring from the engine.

Engine removal/replacement

Engine hoist
Mast bend is intentional pre-bend plus lens distortion ! The boom is raised and supported by the halyard as well as the topping lift. At this angle the main sheet falls neatly into the hatch if pulled forwards.

Engine in mid air

engine in air
Engine in mid air : snap shackle is normally on traveller : for MOB use as well as for this kind of work. This picture is on the way back in. Missing paint is "Hammerite'd" over. This was the worst bit just after when the engine started pirouetting down the trolley which started rolling down the pontoon finger ! I caught it and stopped it.
The 3 strand rope was taken across to a winch to stop the whole lot swinging further outboard. The weight of the engine heeled the boat so the engine stayed put while I took the picture.

Spline corrosion/lubrication

Although this is a specific fault for some old Volvo engines and not Yanmars it was interesting to see that the gearbox splines were slightly rusty but still square as they were free of grease. I put a little light grease on the splines to make it easier to reassemble : the corrosion made it slightly stiff.

Alternator belt misalignment

I happened to place a straight edge between the two pulleys on the alternator and the engine, looking for reasons why all alternator belts turn into dust in a couple of months, and I noticed that although the planes of the pulleys were parallel they were visibly staggered, as assembled by Yanmar. I note that the alternator type was changed during production.
I estimate the error was more than 0.5mm and less than 1.0 mm. I fitted a pair of washers under the alternator bracket mounts and the alternator belt doesnt seem to be wearing so fast.
I also made sure that the pulleys were corrosion free.

Rotten Gate valve

rotten valve
Note the cracked thread : caused by turning valve to shut when it was leaking. Thread was brittle and failed. Also found gland nut had also nearly fallen off. Waste pipe blocked with grease/deposits from the sink This has now been replaced with a ball valve and new pipes.

Engine sea water inlet replaced with a strainer type that will be less likely to get blocked with a plastic bag, and the gate valve also replaced with a ball valve.

Results

Well, in trials immediately after the engine's return to the boat, it was apparent that the hull speed was back to 5.2 knots with the engine flat out . Less smoke and higher maximum RPM under load were observed.
Then we caught a plastic bag in the River Hamble, ands for a while we we could only manage about 0.5 knots astern and nothing ahead. The shaft knife worked to let the prop keep spinning but the bag stopped the prop from working. Back in the marina probing with a boat hook successfully removed the bag, although it drifted off on the tide underwater, so I never saw it.

Time needed to do work

Engine out : 2.5 hours
Marine Power : one man day
Engine back in 3.5 hours
Cost : about £650 including sundry bits and pieces.

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mike@hamble.demon.co.uk