Sever Idle problem

[Kendog30]

I have a 2004 Horizon 230 with a 5.7 GI-F, engine product # 4012118848, Volvo Penta I/O SX-11. Terrific running rig, Over the past couple of year when we start it hot, engine idles EXTREMELY rough (shakes bad). When you put it in drive smooths out. Recently started doing it when starting cold and also did it once when slowing while docking. When it is not doing this the engine idles extremely smooth and runs great. I have replace wires, plugs, cap and rotor. Checked all electrical connections and removed and cleaned throttle body. Fuel pumped replaced a few years ago after internal paint failure. Thanks in advance for any thoughts on this problem. Marina thought it could be vapor locking (now doing it with cold engine and cool temps)

 

[alldodge]

Howdy

Vapor Lock (VL) happens when motor is at running temps and is shut off. The fuel gets heat soaked and the symptoms of VL is the motor won't start, and may slightly hit but not stay running. When motor is cool it fires right up.

In most cases the motor needs to be scanned for codes, but until then
Your motor has the crab style cap and those style go bad often and show no signs of issues. Now if you just replaced the cap it probably won't be it.
Check for vacuum leaks
Check the connections on the distributer (cam sensor) and the timing chain cover (crankshaft sensor)