Stalling engine when hot (OMC Ford 460)

[seattle2855]

The last two trips out I've had a problem with the idle when coming back into the marina. The trip coming back in consists of 10 minute of high speed and 30 minutes of travel at 1700 RPM. The problem is when I go down to idle after this -- the boat dies.

Luckily I've been able to limp it into the slip. I can always restart it easily and it revs fine, but wont idle. If I let the boat sit for 2 minutes it will idle fine, then slowly over, the coarse of 3 minutes, idle gets worse and worse until it dies. Let it sit for 2 more minutes and the same thing. Again, when it won't idle the engine revs as normal.

Also, the coil feels pretty hot. I'd say 180 degrees by comparing it to the risers. It has the Pertronix? ignition, not points/condenser.

Engine temp was good. Volt meter read 13ish. Oil pressure good.

Carb rebuild? Coil? Electrical issue?

Any ideas?

28' Bayliner 2855
1989 OMC Ford 460 King Cobra
Pertronix ignition

 

[HT32BSX115]

Re: Stalling engine when hot (OMC Ford 460)

Howdy,

Glad you got the overheat problem solved!

You may have a carb problem that might require either a rebuild or an adjustment.

It might even be a sticking and/or maladjusted choke.

If your coil is getting hot, you might have the wrong coil or no ballast resistor. (whomever installed the Pertronix system my not have put the right coil on it or left out the ballast resistor thinking it wasn't needed)

Pertronix does have 12v coils that don't use a ballast resistor.


If you need to rebuild the carb, you can get the kit directly from NAPA. I still have the carb I took off my 460 (right after I rebuilt it ). I got the Kit from NAPA locally and it was about $70 or so.

 

[seattle2855]

Re: Stalling engine when hot (OMC Ford 460)

Yeah, the overheating problem was the impeller housing. The metal lining had slipped so the inlet and outlet holes were no longer where they should be causing restricted water flow.

This stalling issue is interesting in that it only happens once the engine has been used quite a bit. I can let it run for 20 mins no problem. It's only after heavy use. And then it fixes itself with a few minute of cooling. Should make it hard to troubleshoot...

 

[HT32BSX115]

Re: Stalling engine when hot (OMC Ford 460)

If it only happens when you have been running for a while, you might check for high temps in the engine house. If it gets too hot you might be on the verge of vapor lock.

You may be able to run the bilge blowers all the time to reduce "under-hood" temps.

You also may have a partially clogged fuel pickup (in-tank) strainer or sticking anti-siphon valve which would make the system more susceptible to vapor lock because of the increased suction to get the fuel out of the tank. I'll assume you already checked your fuel filter etc....


Gasoline has a vapor pressure of around 7-9psi depending on time of year. If you heat it up the vapor pressure drops accordingly.

Place it in a vacuum and the vapor pressure drops significantly.......add heat and it'll boil in the fuel line if there's enough heat and vacuum.

 

[seattle2855]

Re: Stalling engine when hot (OMC Ford 460)

Interesting about engine compartment temps. The two time it's happened were last week when it was 104 degrees and today when it was about 90.

I just changed the water fuel separator. Is there another fuel filter somewhere with the 460?

 

[HT32BSX115]

Re: Stalling engine when hot (OMC Ford 460)

There's usually a small screen right at the carb but they almost never get anything in them because they're after the regular "spin-on" filter.

I pulled mine after nearly 20 years of running and it was completely clean. It had never been off prior to that....

If you have really high temps in the engine compartment area you may be having a vapor lock.

Does it do any of this after initial warm up or does it only do it after running for a longer time?

You'll have to refresh my memory, is it closed cooled or raw water?

 

[seattle2855]

Re: Stalling engine when hot (OMC Ford 460)

Its a half closed system. I've only had this problem after running it for 30+minutes.

Only happens after heavy use. I usually spend about 40 minutes heading out, drift for a few hours, and then another 40 minutes back in. I've only had the problem on the way back in. Idled fine after the trips out (to lake washington)

 

[HT32BSX115]

Re: Stalling engine when hot (OMC Ford 460)

Have you had a close look at the clear plastic tube that runs from your fuel pump up to the carb? Anything in it? If it has any sort of liquid in it you might have the start of a fuel pump diaphragm failure.

 

[seattle2855]

Re: Stalling engine when hot (OMC Ford 460)

The clear plastic tube didn't look like it had anything in it.

I just checked the fuel tank vent and the screen was pretty clogged up. I noticed it seemed to be venting for several seconds after gassing up. I could hear a "whish..." noise for 5 - 10 seconds.

So if I had a vapor lock, would it makes sense that it would only be an idle problem? Does the vapor lock cause the bowl in the carb to be dry? If so, would I be able to kick up with RPMs by giving a little throttle?

It almost seems like I don't have enough vacuum to suck the gas down the carb at idle. I don't know what would cause that.

 

[seattle2855]

Re: Stalling engine when hot (OMC Ford 460)

Anyone know what the correct carb is for an OMC 460? Not sure if it should be 600 CFM or 750 CFM

 

[HT32BSX115]

Re: Stalling engine when hot (OMC Ford 460)

So if I had a vapor lock, would it makes sense that it would only be an idle problem? Does the vapor lock cause the bowl in the carb to be dry? If so, would I be able to kick up with RPMs by giving a little throttle?

Vapor lock usually doesn't happen at idle......although it could. You may have some sort of debris in the carb plugging the jets such that it doesn't want to idle. Also, you may have a vacuum leak. I seem to remember mine running crummy at idle if the PCV valve connection was disconnected.










This is the one that came off mine. As far as I know it came on it new. According to the Holley "LIST" number it's a 650.
http://www.holley.com/data/TechService/Technical/Carb Numerical Listing.pdf