2015 Yamaha 200HP Inline 4

I have a 200 HP with50 hours and after I run the engine for about 10-20 min at 80% RPM the engine will have a slight misfire during idle and cruse speeds. This misfire appears after its warm and does not appear when the engine is cool. I have had the engine in the shop they cannot find anything. Could it be the plastic filters that are on the lower end unit have smaller holes, which would not permit enough water to the pump.

20pacnav said:

Could it be the plastic filters that are on the lower end unit have smaller holes, which would not permit enough water to the pump.

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No. A obstruction/restriction in the cooling system would not cause the engine to sputter/miss as you've described. This sounds fuel system related, as the majority of outboard engine issues usually are.

Thank you for your reply. I have replaced the fuel filter and did not show any improvement. I had a Yamaha service center run diagnostics on the motor and they could not find anything. This all star Happening after add about 15 miles an hour I had some soft mud. If I take the boat out of the water and wait a few days and put it back in the water it's good for about a 15 to 20 minute 80% run and then it acts up all afternoon at any speed. it's just on intermittent miss but it feels strange when you're cruising. I really appreciate you taking the time to respond.

The service centers diagnostic test would probably not turn up anything for what you've described. It would require a tech to get his hands on the engine and troubleshoot. If the service center you went to couldn't fix the problem I'd find another Yam service center who will put in the effort to find the issue. What you're describing isn't normal, and the engine should not continue to be run until it's fixed. If not, the problem will indeed become worse.