drpete3

Started the boat today and ran fine. One of the first times out this year. After running about 15 miles w no troubles when I pulled it out of gear I was running about 400 rpm high. Now it continues to Idle high. On port engine.

I'm wondering about a vacuum leak as well as maybe something from old gas. I haven't done anything to check this. What should I do first? Btw engines are pretty new. Only about 20 hours on new engines. They are NA 600 cu in w Holley 4150 carbs. The other engine is fine. Help. Don't want trouble for the 4 th

jbraun2828

Make sure your throttle cable is pushing the carb all the way closed , sometimes they get hung up. You may need to adjust the cable a little.

CNC

I've been down this road...most likely a vacuum. First check all vacuum lines, either cracked or disconnected. Next is more complicated, a sucked in gasket somewhere in the intake system, carb or intake manifold. But BEFORE you do anything make sure throttle is returning to the throttle stop on the carb.

Randy

Revinchevy

Sounds like a vacuum leak to me. Easiest way to find it is spraying starting fluid around your gaskets. Just make sure ya gotta fire extinguisher!!!

drpete3

Ok I have all the stuff to check for a vacuum leak. I did take 10 seconds to look at the flaps and it does appear that the engine that has higher idle is a touch more open than the other. I am going to look at it rite after work today.

drpete3

I also did as you said looked and the top is sitting on the adjustment screw.

hotjava66

Does it only happen while warmed up? If so idle circuit may be lean. Either that or linkage or idle screw out of adjustment or vacuum leak as stated above. Use carb clean to find vacuum leaks.

28Eliminator

Also verify that the secondarys are all the way closed. I have had them stick a couple of times over the years.

CNC

Just curious if you found the problem...and what it was?

drpete3

Well no one including myself guessed the problem rite. Turns out its an occasional stuck lifter. This in on engines that have 20 hours. Talked to my builder. He to,d me I need to take it out and at some point get it on the rev limiter. He said 90 pct chance it will free it up for good. He said its fooling the engine the it has a smaller cam. At least I think that's what he said vs larger. Anyways that's what's causing the inc idle. I can get it to go away by decreasing my idle