3.0L Merccarb intermittent idle issue

[sprobst]

Hi Everyone,

I have a 1998 3.0L with a Merccarb carburetor. I've been chasing an intermittent problem for 2 years.

The engine starts easily, idles fine initially, and runs great at cruising speed.

Occasionally, however, after running at cruising speed for a while (after the engine is good and warmed up), when I back it down to idle, it'll idle rough for a while, and will eventually die after a few minutes. This doesn't always happen but happens frequently enough to make my wife nervous about the reliability of hte boat.

This happens even when I gradually come back to idle. It'll normally starts right back up with no problem and will idle fine after that.

Last summer, I rebuilt the carburetor making sure I set everything to specs (float level, float drop, idle mixture, idle speed). After the rebuild, I haven't noticed any real improvement.

If the boat idles fine when cold and idles fine when hot (sometimes but not all the time), what should I be looking for?

 

[playpool]

Re: 3.0L Merccarb intermittent idle issue

check silly things like the fuel filter. Mine was crusty/crushed and about 15 years over due. It sounds like your getting the grip sort of.

 

[89sandman]

Re: 3.0L Merccarb intermittent idle issue

i would pull the spark arrestor off and see if for some reason maybe the choke isn't working quite right. old carbs are just that, old, even when rebuilt they often never work again as when new. can't wait till the day when theres not one left on the planet. can't believe boats have taken sooooo long to go efi.

 

[sprobst]

Re: 3.0L Merccarb intermittent idle issue

Thanks for the responses. I'll take a look at the choke the next time this happens. The fuel filter was replaced last season....but it's probably due again too. I don't have a water separating fuel filter. I have considered installing one, this season (for good measure) but I doubt that is the source of this problem. I may still do it.