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Mikeh277
09-01-2010, 02:13 PM
I have a 1985 stars and stripes 351 and the engine will not stop back firing. Also it is not getting the right charge off of the alternator. If the blower is on the lights will not work until the blower gets shut off.

The coil has been replaced
Carb rebuilt
Fuel line replaced
Fuel Filters replaced
New cap new rotor
New battery
Timing adjusted

Any help. Thanks

03geetee
09-01-2010, 04:25 PM
I have a 1985 stars and stripes 351 and the engine will not stop back firing. Also it is not getting the right charge off of the alternator. If the blower is on the lights will not work until the blower gets shut off.

The coil has been replaced
Carb rebuilt
Fuel line replaced
Fuel Filters replaced
New cap new rotor
New battery
Timing adjusted

Any help. Thanks

What is the timing adjusted too?

What octane fuel?

Are you sure the firing order is correct?

Plug Gap?

Just few things to get some more information.

Thank you.

JTR

thatsmrmastercraft
09-01-2010, 04:43 PM
I would bet on the firing order being wrong, but you will probably need to get the electrical issues resolved before trying to make it run. A bad ground or two could cause most if not all your problems.

Mikeh277
09-01-2010, 07:43 PM
The firing order is correct that was checked. The timing is adjusted to 6 degrees. I am using 91 octane. The only thing that I have not done is check the gap on the plugs. I know the electrical problem is an issue but we bought the boat 10 years ago now and it has always been the issue. This problem started the beginning of this season with a clogged fuel screen, once that was fixed we could not get it to stop back firing and popping. Any other suggestions before I go back up this weekend and check it out?

03geetee
09-01-2010, 08:11 PM
The firing order is correct that was checked. The timing is adjusted to 6 degrees. I am using 91 octane. The only thing that I have not done is check the gap on the plugs. I know the electrical problem is an issue but we bought the boat 10 years ago now and it has always been the issue. This problem started the beginning of this season with a clogged fuel screen, once that was fixed we could not get it to stop back firing and popping. Any other suggestions before I go back up this weekend and check it out?

If the fuel screen was clogged some of that debris may have made it to the carb. But I am also leaning towards what Mr. M said if the coil is not firing at full strength, or not at all your engine may run just like you are describing.

It may also be a combination of the two, check your plugs and see what they look like if they are not firing properly they will look black and fouled out as they will not be igniting the mixture properly which then snowballs into worse firing as the plugs deterioration more.

JTR

1985 Skiier
09-01-2010, 09:19 PM
There are two types of backfires, one is in the intake (combusition bofore the valve closes, (too lean) and backfire in the exhaust (too rich). Both are usually a carb problem. Replace your plugs they are cheap and then you can rule them out. Coils are cheap too, then if your timing is on, You need to adjust your air fuel mixture. It sounds to me like it is a good time to buy a carb rebuild kit and go for it. As soon as you are done it is easy. The first time is always a bit scary.

Good Luck

gr82bgreen
09-01-2010, 11:29 PM
I have a 1985 stars and stripes 351 and the engine will not stop back firing. Also it is not getting the right charge off of the alternator. If the blower is on the lights will not work until the blower gets shut off.

The coil has been replaced
Carb rebuilt
Fuel line replaced
Fuel Filters replaced
New cap new rotor
New battery
Timing adjusted

Any help. Thanks

Bad or worn points may cause a backfire. If you don't have electronic ign conversion, now would be a great time to do the conversion.

thatsmrmastercraft
09-01-2010, 11:42 PM
Bad or worn points may cause a backfire. If you don't have electronic ign conversion, now would be a great time to do the conversion.

At least verify that the dwell is set correctly. 26 - 31 degrees is the correct range I believe.

Mikeh277
09-02-2010, 09:15 AM
The conversion from points have already been made. I am going to try everything else that everyone recommended and I will let you know after the weekend how it works out.

oldairboater
09-02-2010, 09:38 PM
Check compression on all cylinders.