I have a v150tlr. Motor idles fine, comes out of the hole great and mid range is fine but when I open it up all the way it’s missing and not gaining full rpm and speed. Though every once in a while it will. Initially when I got the boat I had some major bogging down issues. Performed a lot of test that I could. Things I changed out for new were the fuel lines goin from tank to the engine, removed anti siphon valve, new primer bulb, water/fuel separator, filter under cowling, fuel pumps, new spark plugs. Even had it a good Yamaha mechanic that did a multitude of tests and checked out the stator, put a new crank position sensor in and even checked it out with a new ECU and the problem still was there. He eventually swapped out the bottom carb for a new one and he thought that fixed the problem.
Well when I got it back from him the condition did improve for sure as it wasn’t bogging down as much but there was still an issue. So after all that I pulled the top 2 carbs, put them in an ultrasonic cleaner and rebuilt them. For a while over this mild winter I ran the boat at least once a week and the boat seemed to be running fine holding around 5700 rpm, with every once in a blue moon where it would only reach 5100 rpm.
The last few times out even after putting a new tempest plus 23 p prop on there and then goin back to the old yammy 23 m prop for clarification, the engine starting acting up again at wot. It only reaches that 5000 to 5300 rpm range AND every once in a while it will open up to 5600-5700 rpm and top speed but back down again. You can hear the engine it missing like it’s trying to open up but won’t.
Im just stumped, any ideas or suggestions. I’m about to purchase some new fuel OEM fuel lines (the little gray ones) that go from fuel pumps to the carburetor to see if that makes a difference.