99 Speedster problems / hard to start, idle problems and died at 75% throttle

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nman729

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As the title states, I had my speedster at lake Erie today and experienced hard starting on both engines, however the port engine was worse. Also port engine wants to die at idle or just above idle speeds after around 5-10 minutes (for example traveling through a no wake zone) and it died on me twice at about 30 MPH on the lake today. Starboard engine seems OK. It was a bit hard to start today, but gives no other problems.

The idle issue with the port motor has been a problem since I purchased the boat (~7 trips this season). However the hard starting has gotten progressively worse with both engines as the season has went on. And the 30MPH engine cutting out has only happened today.

So far I have replaced the plugs on the port engine during the trip before this one on the water after about 5 minutes of unsuccessful cranking. After replacing the plugs on the port motor it started right up without any issues. Today was the first time out since I replaced the plugs and had these problems. I plan on replacing the inline fuel filters and see where that gets me next trip, I just dont want it to fail out on the water. I am running regular 87 octane, so maybe I will try the 93 octane and add some sta bil and see if that does anything. Anyone have any suggestions or ideas?

Another problem I noticed that may be unrelated is that the water regulator on the water box (port side) comes off very easily. I bumped it with my shoe while working in the engine compartment and it popped off. I popped it back on easy enough but should I be concerned?
 
When it doesn't start and you pull the plugs are they wet or dry? I have went thru this exact same issue with my boat. Rebuilt all carbs with oem parts and new needle seats still hard start. It ended up being excessive rotary cover clearance.
 
Plugs were dark and wet when replaced. Can you elaborate a bit more? What is excessive rotary cover clearance?

Never mind, I found this and i will try checking the valve cover.
 
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When checking the valve cover clearance, is it the valve cover or the valve itself that needs replacing?
 
If clearance is excessive cover needs to be replaced. If the valve has deep scratches it also needs to be replaced.
 
OK, I sprayed some seafoam in the carbs while it ran and also cleaned the air vent covers. Replaced fuel filters, oil filters, spark plugs and cleaned rave valves. It does start better, no more hard starting in either engine YAY! But she still dies at idle (maybe an idle screw adjustment needed?) and will bog down at 3-4k RPM if you don't accelerate hard.
 
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