PDA

View Full Version : Engine won't idle and runs rough when hot


skilew
07-18-2011, 05:57 PM
Ok I need some help trying to figure out what is going on with my boat. It has a 1993 Ford 351 engine rated at 285 hp with carburetor. First thing when I start the engine and it is cold it runs great. But after about 10 to 15 minutes it will not idle and runs rough.

I have replaced the coil and rotor button and have even replaced the carburetor with a rebuilt one but no change. Any suggestions?

thatsmrmastercraft
07-18-2011, 06:07 PM
Vacuum leaks at carb base or intake manifold.
Choke set too rich.
Fuel filter clogged.
Fuel line from tank to fuel pump collapsed.

j.mccreight@hotmail.com
07-18-2011, 06:19 PM
Distributor is crapping out, is my guess

skilew
07-19-2011, 04:12 PM
Vacuum leaks at carb base or intake manifold. (No)
Choke set too rich. (No)
Fuel filter clogged. (No)
Fuel line from tank to fuel pump collapsed.

I have installed a new fuel filter.
Installed a rebuilt carb.
Only happens after I run the boat for about ten minutes when it's hot.


I think it is ignition related.
How do I know if it is distributor issue?

cbryan70
07-19-2011, 04:18 PM
what carb is on the motor?

skilew
07-19-2011, 04:33 PM
Just installed another Holley 4160

thatsmrmastercraft
07-19-2011, 04:48 PM
So I understand your skill level, I assume you are checking for vacuum leaks with carb cleaner.

Have you pulled a couple spark plugs to see what they look like?

Electronic ignition I presume?

cbryan70
07-19-2011, 05:05 PM
Whats the choke look like once the motor is hot?

skilew
07-20-2011, 03:26 PM
No vacuum leaks.

Choke is straight up no problem when hot.

It is electronic ignition.

Tried it again last night at home in the drive way. It ran perfect. But it was not under a load and running cool tap water through it prevented it from getting hot like it does when on the lake.

I am still leaning toward an ignition problem and I am about ready to buy a new ignition module.

gimmemoedmb
07-27-2011, 02:17 PM
Your problem doesn't sound exactly the same as mine but it's probably worth a try for 10 bucks.

http://mastercraft.com/teamtalk/showthread.php?t=41681&highlight=idle

Hawksinkalispell
08-02-2011, 11:14 AM
Have you cleaned your spark arrester, won't hurt and it's cheap and easy. Mine wasn't idleing once it was hot, I think it's cause fuel is burning better but then it didn't have enough air.

BallBushing
08-02-2011, 01:04 PM
If you have a transmission cooler on that engine, check for debris at the inlet screen. Mine would run fine at idle all day but as soon as the boat was put in gear would overheat the transmission and shut it down.