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Westerbeke (Bukh) DV20 Question

May 24, 2010
Bristol 32 Buffalo
My 1975 Bristol 32 has a Bukh DV20 marine diesel. At the end of this season I had a hard time getting it to turn over and start. The batteries are new and fully charged, and the alternator was checked by a mechanic and seems fine. My boatyard guy looked at it and suggested that something might be wrong with the regulator, which stands between the battery and the alternator (picture below). Is this likely and should I replace the regulator with something more robust? If so, what would be compatible with my DV20?

Many thanks,


Nov 6, 2006
Hunter 34 Mandeville Louisiana
Looks to be a plain old external automotive regulator.. If ya take it to a good auto parts place, they can supply an electronic "generic" that might be adjustable for volts.. Your alternator is probably in the 30-40 ampere range so almost anything automotive will work..
Dec 31, 2016
Beneteau Oceanis 351 Charlottetown
If the batteries are fully charged and it still won't turn over it's not your regulator. I'd start checking voltage at your starter first.
May 24, 2010
Bristol 32 Buffalo
The engines does turn over, but very slowly - it's like it wants to start but can't build up the rpms. I had the started checked out by a professional and he said the starter was fine. Should I "upgrade" the regulator and, if so, to what? I know next to nothing about electronics.



Feb 5, 2004
Tartan 3800 Westport, MA
Do you have a decent voltmeter, like a DVM (digital voltmeter)?

Are you plugged in, and charging at a dock?

Before the next attempt at starting, measure the voltage at the battery. Should be in the neighborhood of 12.6 Volts. Don't proceed it it's 12.4V or less.

To check the regulator, just measure the voltage at the battery when the engine is running. Should be anywhere from 13.6 to 14.4 Volts.

If it's above 12.4V and cranks slowly, and, the starter was checked and found good, the problem is the electrical connection from battery to starter. Check the cables and terminals - tightness, corrosion, broken strands of wire, etc.

Check the engine ground, too, a bad ground can cause this problem, too.

Check to see if there are any intervening switches between battery and starter.

Another thing, most starters have integral solenoids, and its possible to check a starter motor while bypassing the solenoid. Make sure the solenoid is working and that it is not providing a high-resistance connection to the starter.

One good place to start is the get alligator clip leads for the meter, and measure the voltage at the starter motor while you are cranking it. You can also check that the voltage between the solenoid terminals goes to just about zero when you are cranking. If not, you have a poor solenoid connection.

In the end, these things are usually a poor connection of some sort.
May 24, 2010
Bristol 32 Buffalo
Thank you very much! I will do just as you suggested, once the winter cover is off next spring (I'm in Buffalo, NY). Just earlier this month, to get it started so I could winterize, it took one guy hand cranking while I fiddled with the ignition! Not fun, to say the least.

Thanks again.