1984 90 hp 6cyl stalls at idle

Motor starts and runs fine for a few minutes, then stalls (can watch the fuel drain out of the fuel filter b4 it stalls). If you keep squeezing the bulb it will continue to run. If put in gear and revved it will run above idle with out stalling. Also stalls when it's in gear idling into dock after running out on the water, above idle, indefinitely. I am working on the idea that there is a vacuum leak, or the carbs have issues. There is some fuel seepage around the carbs, dripping off the bottom and coming out the throat after it stalls.
I have checked the tank vents, tried running it with a different fuel tank, rebuilt the fuel pump, replaced all the fuel hoses and vacuum hoses. Compression is good on all cyls.
Any ideas would be appreciated.
Thanks.

Re: 1984 90 hp 6cyl stalls at idle

Being that you can see the fuel drain from the filter before it stalls seems to confirm a fuel pump issue. It sounds to me like you're getting weak vacuum to the fuel pump at an idle - it's possibly a very small vacuum leak, causing the pump not to work well at an idle, but not being a big enough leak to make a difference with the increased vacuum at higher rpm. I know you said you've rebuilt the fuel pump, but I would re-check the diaphram and the last gasket (engine side) to see that it's not leaking. Have a look at the gasket surfaces as well, and make sure they're clean and not scratched or damaged.

Re: 1984 90 hp 6cyl stalls at idle

Here's some info from a Mercury Marine Advisory Bulletin (# 99-5 of Jan 2000) about fuel starvation which might help:

"The current style check valves used in the primer bulb may stick closed, causing a fuel restriction.

This is more likely to occur at idle speed, in HOT weather conditions or when using winter blend fuels. A new primer bulb P/N 13330A5 has been developed to help resolve this condition.

The new bulb uses a round check ball and spring arrangement, rather than the
current shuttle style check valve."

There's also some excellent info in the Bulletin about checking for fuel restrictions which could cause starvation issues.

Here's 3 really good fuel starvation threads at this site:

http://forums.iboats.com/showthread.php?p=1610291

http://forums.iboats.com/showthread.php?t=224246&highlight=fuel

http://forums.iboats.com/showthread.php?t=215710

One of these posts used to have a link to the Merc Bulletin, but the page on the web site was taken down.

If you'd like a copy, I can forward the .pdf file to you if you'll drop me a Private Message here with your e-mail address listed.

Cheers...........ed

<edit> OK found another post that has .jpg scans of the bulletin, here's the link: http://forums.iboats.com/showthread.php?t=261581