(Updates with results of final in first 3 paragraphs)
* Afd founder Lucke urges party to drop 2 of its 3 chiefs
* AfD not small-time bowling club or 'rabbit-breeding society'
* Eurosceptic party expected to win seats in Hamburg election
By Erik Kirschbaum and Michelle Martin
BREMEN, Germany, Jan 31 (Reuters) - The eurosceptic Alternative for Germany (AfD) party that has been siphoning votes from Angela Merkel's conservatives voted narrowly on Saturday to support a demand by founder Bernd Lucke to stop making itself look foolish and choose a single leader.
Lucke's proposal to change several AfD party rules - including eliminating two of the party's three leaders by the end of 2015 - just barely cleared the two-thirds majority threshold with 1,001 of the 1,473 delegates voting in favour.
"We've put this troublesome chapter behind us and won a constructive result," Lucke said after a 12-hour debate.
Lucke had warned delegates in the northern port city of Bremen that the AfD, Germany's fastest growing party that has soared to 7 percent in national opinion polls, needs to dispense with its tripartite leadership in order to succeed.
"We're not a bowling club or a rabbit breeding society that we can run in our spare time," Lucke said in a speech. "How did the party leadership work these two years? Here's my one-word answer: 'Botched'. We can't continue like this."
The other two leaders, Frauke Petry and Konrad Adam, voiced reservations about what they saw as Lucke's grab for control after the AfD scored stunning wins with an anti-foreigner tack in three east German regional elections in late 2014.
Some 3,500 anti-AFD demonstrators held a boisterous rally outside the congress hall, attacking the party for what they say is its flirt with the far right that breaks post-war taboos in a country that has deep sensitivities about its Nazi past.
"Live better without Nazis" read one of the banners. Scores of AfD supporters confronted protesters by singing the German national anthem from a balcony but a proposal for all to go out and sing the anthem, or Deutschlandlied, was not approved.
Under a deal reached by the party executive, any move to a single leadership would be taken in stages, switching from three leaders to two in April and then to one in December. Votes on who will ultimately lead the party will be made later this year.
Many delegates to the at-times raucous congress spoke out against Lucke, reflecting divisions in the AfD between its anti-euro zone bailout founders and the increasingly powerful eastern wing that wants to attract far-right voters.
Chancellor Merkel and her Christian Democrats hope the AfD, founded by Lucke and other ex-CDU members upset over her pushing the party left, will self-destruct over their internal strife.
But renewed euro zone turmoil heightens the AfD's prospects of winning seats in a Hamburg regional election next month.
Lucke has fought a spectacular public battle to demote his two co-leaders, who are popular with the AfD's far-right wing. They called Lucke a "control freak" with a "despot-like style of leadership" while his allies denounced his naysayers.
"We'll make ourselves look ridiculous to the voters," he said. "I'm not doing this for personal power but because I want the party to succeed." (Editing by Dominic Evans, Bernard Orr)