Misfireing 1994 SN196

I can report back after a full tank of fuel yesterday ( and some aching arms and a very sunburnt face) that the new coil seems to have fixed my misfire!! Happy days. Thanks for the help guys.

Only the coil would be affected by the higher current (no ballast resistor).

BTW, an old ignition guru pointed out to me that the Presotlite EI system does not take a ballast resister. Maybe it is coil specific, dunno.    I have the prestolite EI + same coil you are getting, no ballast resistor, works great.

The PCM "GT40" was the multiport EFI version of the 351w HO, it came out in 1995. The carb and TBI versions of the HO were called "Pro Boss" (the GT40 also got the Pro Boss label but generally wasnt referred to as such). All HO 351w's came with cast iron Ford GT40 heads.

GT40 and GT40P heads share some similar design elements since they are both factory cast iron heads, but they are NOT the same. While they are a popular aftermarket upgrade for people like us, they were never offered by PCM or any other marinizer as a factory option, as far as I am aware.

Both GT40 and GT40p headed 351w's tend to run best when propped to turn in the 4800-5000rpm range.

89Martinique wrote: was it a GT40P HO? If so, I would make WOT around 4,600 rpm.

There is no such thing as a "GT40p HO" that came from any of the marinizers. 4600 is also the wrong RPM to be targeting for a boat equipped with GT40p heads.

Post some pics. Did it used to be EFI?

Is it, or was it a GT40P HO? If so, I would make WOT around 4,600 rpm.

wake_2001 wrote: Any news? I'm having the exact same problem you describe. Runs PERFECT until it's hot then coming out of the hole it will sputter/miss until the rpm's get up. Hard to start too. I've tried the wide open throttle with no luck as well. My only problem with getting a new coil is I'm not sure what EI conversion kit I have. I'm learning as I go. Pretty sure I don't have an external resistor though.

Guys,

Sorry for the dealy with a mixture of crap weather and me having 'the man flu'.

However im pleased to report last night I got a new coil on it and now all seems to be well. No misfires or alike.

Just for Ref what is the max RPM of the 351 Windsor ( SN 196 1994 Red rocker covers)
Im running LPG and you can easily over fuel them and makeing them rev to stupid revs.

Any news? I'm having the exact same problem you describe. Runs PERFECT until it's hot then coming out of the hole it will sputter/miss until the rpm's get up. Hard to start too. I've tried the wide open throttle with no luck as well. My only problem with getting a new coil is I'm not sure what EI conversion kit I have. I'm learning as I go. Pretty sure I don't have an external resistor though.

Fly100 wrote: Bri892001 wrote: a carb that's dripping fuel out of the primaries when the motor is shut down can make restarts a little tough as well. Its not the carb as a new one was fitted

This is not the proper way to diagnose a problem. Ive seen plenty of new and freshly rebuilt carbs drip after shut down. Far and away the most common "hot starting issue". Take a look down the throat before you spend a dime on any parts.

It misses up to about 3k then as boat starts to plane and the load comes off she runs clear.

I have seen faulty ignition components cause issues before, but very rarely will an ignition issue cause the engine to start hard and then run better at higher RPM.

While a few people in the know have said that some of the early Multiport EFI (GT40) engines can heat soak under the right conditions, I have never seen it with a carb. The described symptoms are nearly always a post shut-down fuel drip.

Let me guess- if you shut down and restart right away, its not an issue. If you give it a minute or 2, then its problematic. Leave it for an hour or more (or overnight) and its fine. Scenario #1 happens because the drip hasnt had enough time to flood the engine. Scenario #2 happens when it does. Scenario #3 is when the fuel has enough time to evaporate off the intake manifold before you attempt to restart.

Next time you have an issue and are too lazy to pull off the flame arrestor, try opening the throttle all the way. Do not pump it, just open it. This will introduce more air and allow it to start. Keep the RPM's high (1500-2000) for a second or 2 and it will clear out the extra fuel that dripped down post shut off.

backfoot100 wrote: Fly100 wrote: So runs fine until its warm, stop for a few mins and then it starts playing up. Am guessing the its getting heat soaked under the hood. Agree with Brian. Are you having misfiring or hard warm starts after shutdown. Two completely different scenarios with completely different troubleshooting.

Starts fine just a misfire when hot ( worse after it had a few mins standing after a run (make me think of heat soak))

FLY

If its on its side I'd say that's the problem. Side mounting those coils is just bad mechanics. More than likely the damage is already done as the fluid has probably leaked out over time. Luckily coils are cheap.

Generally speaking the coils operate fine cold, but as soon as they heat up they don't have enough fluid in them and begin to act up. classic symptoms of when one has cracked and/or leaked.

I wouldn't rule out the coil just yet even though it's fairly new. If it's oil filled and laying on it's side, it could be the problem.

I agree with Chris that the coil is one likely suspect.

A little more info on the exact circumstances would be helpful though. Like, if you kept driving the boat without shutting down, would you ever have a problem?

I ask, because a carb that's dripping fuel out of the primaries when the motor is shut down can make restarts a little tough as well.

More woes and the love of owning a boat ....Misfire now.


So runs fine until its warm, stop for a few mins and then it starts playing up.
Am guessing the its getting heat soaked under the hood.

New plugs so far, cap and rotor arm are ok. Its got the protec conversion to Mallory on it, approx. 4 years old everything was new then ( leads etc etc.). Its not fuel sure its some sort of heat failure.

Coil ? its warm but not really hot ?

Once again any thoughts ??

Cheers

FLY