I was idly leafing through my Bukh manual when I noticed the diagram of the gear control showing which direction to move the lever to engage forward or reverse gear as required. I suddenly realised that the lever on my boat worked the opposite way around. It seems perfectly logical in the cockpit, move the lever forward to go ahead etc. I riffled a bit more and came to the engine spec page where it said the engine rotation was anticlockwise looking forward. But my propeller rotates clockwise for ahead not anticlockwise. I have owned this boat for four years and I've only just noticed that my engine is going astern to go ahead! The diameter and pitch seem correct for a normal installation, but the ZF gearbox has a ratio of 2.77 astern and 2.5 ahead - maybe this is why I can only get about 5 1/2 knots.

Yours, looking back to next year, Neil

Neil Sinclair

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I was also a little bit astonished, when reading the manual, but anyway, the construction works. Although I think you should reach at least 6 knots (forward). Does the engine reach its max. revs.? What kind of prop is installed (2 or 3 blade)? Is the diameter correct or does the prop produce cavitation? Have you ever checked the compression of the cylinders?
Gerold
Gerold Wallenstein

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I have a 16X12 2 bladed fixed prop. The engine achieves about 2,700 rpm - but this is the same with or without load. There is no sign of cavitation.

Cheers! Neil

Neil Sinclair

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Really strange! Even without load no more than 2.700 rpm?
Can the "accelaration cable" (I don´t know the correct english name) be moved the maximum way? Perhaps the limitation screw on the gear box has to be adjusted?
If not, it seems your Bukh is getting old.
If the last 300 rpm cannot be reached, the "12" of your prop (the ratio??) could be too high for the engine.
Best regards
Gerold
Gerold Wallenstein

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Gerold

Now I come to think of it, there is a length of 'dead' travel on the engine throttle quadrant before the revs increase. perhaps the lever has slipped on the shaft? I won't be able to investigate this for some time, since I have the electrics and gear contol dismantled.

The engine was built in 1977 and runs well, although starting in cool weather takes some time. I guess compression is not as good as it could be since there is always some grey gunge under the rocker box that indicates gas blowing past the pistons. It doesn't burn any oil.

Any thoughts on the gearbox running in reverse? It has obviously been so for many years, if not from new.

Cheers! Neil

Neil Sinclair

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I´ve got the same engine from 1977, and it works without problems. Indeed, the engine turns anticlockwise and the gearbox the other way round. I don´t know why, but if it would turn lefthand, you would need a LH-prop, too. Normally british boats have mainly LH-Props, german ones RH-props, boats with two engines use to have one turning LH and the other RH.
Or is there a misunterstanding? Do you perhaps have to move the lever astern to get the boat ahead? Then you would just have to introduce the cable on the gearbox from the other side.
Best regards
Gerold
Gerold Wallenstein

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NB: The different ratios cannot be the reasons for the reduced speed. I think it´s because the prop usually does not work astern as effective as ahead. If you would put the 2.77 ratio to the ahead gear, the prop would make even less revs! (It´s a negative ratio!, the engine makes 2.77 rev. while the prop is making 1.)
Gerold Wallenstein

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Hi Gerold

Yes, according to the Bukh handbook gear lever illustration, engaging 'forward' gear makes my boat go backwards. Your comments remind me, though, that the book specifies 'engine rotation' not 'output shaft rotation'. When I get the gear quadrant back together, I will make an experiment to check which gear selection gives the 2.5 ratio.

As a matter of interest, can you start your engine by hand, from cold? The Lister diesel in a previous boat always sprang into life as soon as it popped over the first compression stroke, but on a cold morning the Bukh needs to spin on the electrics for about 30 seconds before it will run. I have extended the starting handle so that I can get both hands on it - but from cold - no chance!

Neil

Neil Sinclair

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I have never really tried to start the engine by hand, only once I tried to move the handle a little bit just to see, how it works. I have never made any other attempt. In the Hanse Boat exposition a few weeks ago in Hamburg I talked with a representative in the Bukh stand and he confirmed that it is really really hard work. So I prefer to buy a power pack to start the engine in case of emergency.
So long
Gerold
Gerold Wallenstein

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Its important to get the right gearbox rotation, for the direction you want to travel, as forward will mormally have 2 gears involved and reverse will have 3 gears involved.
If you use the wrong way, the gearbox could be under extra stess and generate more heat.
Mike Edwards

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I was concerned for that very reason. Over the holiday, I managed to connect the gear change cable up again and conducted a little experiment, counting the number of rotations of engine flywheel and output flange for each gear selected. I found that the ratio is correct for my installation - that is 2.5 for forward and 2.7 for reverse.

Cheers! Neil

Neil Sinclair

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