* FX becoming negative for Japan exporters as yen fall ends
* Weaker emerging market currencies pose headache
* Honda expects 2014/15 net profit to rise just 3.6 pct
* Mazda forecasts 2014/15 net profit growth of 18 pct (Recasts, adds information about Mazda, quotes)
By Yoko Kubota
TOKYO, April 25 (Reuters) - Japanese carmakers Honda Motor Co and Mazda Motor Corp are forecasting a sharp slowdown in profit growth as a fall in the yen that has boosted earnings in recent years comes to an end and some emerging market currencies weaken.
Honda, Japan's third-biggest automaker by sales volume, said on Friday it expected net profit for the year ending March 2015 to rise just 3.6 percent to 595 billion yen ($5.8 billion).
That is below analysts' average estimate of 22 percent growth and a fraction of the prior year's 50 percent increase.
Mazda, whose net profit quadrupled in the last financial year to a record 135.7 billion yen, said growth this year was likely to decelerate to 18 percent.
The yen, which dropped 25 percent from November 2012 to the end of last year under the reflationary policies of Prime Minister Shinzo Abe, has since stabilised, while currencies in emerging markets such as Brazil and Thailand have weakened.
That is bad news for Japanese exporters and global manufacturers, typified by automakers such as Honda, Mazda and Toyota Motor Corp, many of which have been lifted to record profits as the tumbling yen boosted the value of their overseas earnings.
Honda said currency factors, which boosted its operating profit by 288.7 billion yen in the year ended March 31, were expected to cut net profit by 67 billion yen this fiscal year.
Weaker emerging market currencies including the Brazilian real and the Thai baht are seen cutting profit by 15 billion yen, while an assumed slight rise in the yen against the U.S. dollar is expected to erase another 10 billion yen, it said.
That harkens back to the bad old days before "Abenomics", or Prime Minister Abe's economic policies, when persistent yen strength weighed heavily on Japanese exporters' earnings.
Japan's Denso Corp, the world's second-largest auto parts maker, said it expected net profit to fall 13.7 percent this financial year after rising nearly 60 percent in the last one.
Mazda said foreign exchange moves boosted its operating profit by 112.7 billion yen in the year ended March, but would cut earnings by a projected 3 billion yen this year, although an efficiency drive would fuel continued profit growth.
That would still be a respectable showing after a cumulative $2.5 billion in net losses over the four years immediately following the global financial crisis.
"In the last financial year we were able to build a foundation for conducting business more stably from here on," Mazda Chief Executive Masamichi Kogai told a news conference.
The expected slowdown in Honda's profit growth comes as the carmaker strives to meet an ambitious global expansion plan aimed at substantially boosting its share in emerging markets.
Honda is targeting a 11.7 percent increase in worldwide sales to 4.83 million vehicles this fiscal year, powered by sales of a remodelled Fit compact that is being rolled out globally.
That still leaves it a long way, however, from its goal of 6 million vehicles by 2016/17.
"The truth is that the target is challenging at this stage, but our aim is to build a company capable of attaining this," Honda Executive Vice President Tetsuo Iwamura told reporters.
Honda started operating a new Mexico plant in February and expects capital spending in the current fiscal year of 650 billion yen, accounting for about 5 percent of revenue, but down from last year's 726.1 billion yen.
($1 = 102.2350 Japanese Yen) (Editing by Edmund Klamann, Christopher Cushing and Mark Potter)