I have a 2004 Hunter P42 with the Yanmar 4JH2-TE engine. This engine does not have preheat but has always been easy to start when cold with very little cranking and throttle at idle. Lately it has been hard to start when cold requiring 10 seconds plus of continuous cranking with a wide open throttle until it catches. Any idea what would cause the change? Engine has 1800 hours on it.