'00 250 OX66 RPM lose engine dies

I have twin 2000 250 OX66 Saltwater series. I head out offshore early in the morning. The stbd. engine may hickup a couple of times on the run out. I usually go about 30-40 miles offshore. I ***** all day with no problems. When I start to head back in is when the problem gets worse. I usually run about 33-38 hundred rpms. When the boat goes through the waves the stbd. engine will lose rpm and die. There will be a clicking in the throttle handle. Sometimes it will not die. It will just lose rpms and the clicking in the throttle then it will go back up then go back down. it will continue to go up and down. When I get in the inlet it will stop doing that until I push the throttles down. When the rpm nears 4200 it will start doing it again. It is only the stbd. engine. And they both use the same fuel tank. The boat is being diagnost at the mechanics shop. I would like feed back before I spend a $1000 on just trying stuff. Your help is greatly appreciated.

[boats.net]

Might check the Vapor separator tank for trash and debris which would plug up fuel filter in tank. Does that engine get a lot of water spray on it in heavy seas? Have you checked for water in fuel?

I have changed the fuel filter on the engine with the float in it and I have changed the fuel water seperators filters. There were no signs of water or debris in them. I also changed spark plugs.

I would also like to ask. I spoke to a friend of mine his uncle. When I described to him what was happening he said that it sounded like the dog clutch. He is a mechanic but to far for me to bring him my boat. How would I know. If the dog clutch disingaged would the rpms go up first or would it just die down?

[jf123]

I would check the low pressure fuel pumps. If they were never replaced change all six. (three on each engine). Also check the o2 sensor and draw tube to make sure it is not clogged with carbon.

So the tech that I brought the boat to says that I have to clean or replace the fuel injectors and replace the low pressure pumps before he can go any further. He checked the O2 sensor and said it was working.

Thanks, I will try that first and I will let you know how that turns out.