Motor Idles Rough & Wants to Die.

[egleissner]

I have a 1997 PRE2150WT (direct drive) with the Chevy Vortec 350 (307 HP) engine in it. It's been a great boat for me and after I had some of the seats reupholstered it's practically like new. I bought the boat in 2005 from a guy who didn't use it a whole lot and it only has 320 hours on the motor now. He said he had the carburetor rebuilt in 2004. It has always run a litlle rough at idol speed and in neutral before it gets warmed up, but it seems to be getting worse. Now it pretty much just dies if you put it in neutral even after it is warmed up. Idle speed doesn't work, you have to give it some gas. Now it seems to be starting a little harder too. Anything over 1200 RPM's the boat runs like a champ! Is this just a carburetor problem? I loaded it up with carb cleaner and it didn't seem to help. Any suggestions?

[Waterski-Rebel]

Have you tried to adjust the carb? Hopfully that's all it needs.

[egleissner]

Besides giving it a thorough cleaning, I haven't tried anything else. Would you suggest adjusting the throttle cable or I believe there is a screw on the side or the carb that adjusts the feul flow. I have an engineering degree but I am bo no means a mechanic. I changed the plugs and wires at the beginning of last year. It didn't help the idol problem but I did seem to get about another 200 RPM at wide open throttle.

[dogbert]

What about the distributor cap & rotor? You might check it first. If there's a lot of carbon build-up, it's probably time for a new one. Your issue sounds timing related. If the plugs/wires were worn, then that could have had a negative impact on the cap/rotor.

[River Runner]

Sounds like a carb problem to me. If your going to repair yourself you need to buy the proper manual for your application. Its not hard to do but there are specific guides for setting idle speed screw and idle mixture screw. As well as other things to check before that.
Here is a basic guide:

8 Point Carburetor Check List
To ensure that the carburetor is the cause of the problem, make the following checks BEFORE ordering
and installing a new carburetor. If questions 1, 2, 3, 5, 6 and 7 are YES and 8 is NO, the carburetor may
not be the problem.
1. Does the choke close completely before starting? Y N
2. Does the choke open completely during engine warm-up? Y N
3. Is idle mixture screw set correctly? Y N
(Engines with Thunderbolt V ignition must have module locked in
Base Timing Mode).
4. What is the idle mixture screw setting? how many Turns.
5. Is the engine idle speed rpm correct? Y N
6. Is venturi cluster discharging fuel by 2000 rpm? Y N
7. Is a good stream of fuel being discharged by both discharge holes
in venturi cluster when throttle lever is moved repeatedly while the
engine is off.
Y N
8. Does the engine flood at idle? Y N