Thunderbolt IV

[seada]

I am running 4.3 v6 mercruiser with a thunderblot IV ignition system. The engine starts and runs great. It is timed 8 degrees before top dead center. Brand new rochester carb. Brand new fuel pump. Separate battery and wiring to accessories controlled by a blue sea battery switch. No water in fuel tank. Water seperator filter in-line from tank to carb. THE PROBLEM: timing will not advance. checked all wiring, new plugs, new wires, new coil. I thought i fixed the problem last year, but the last three times i went out it progressivly got worse. Now the boat won't go over 4 miles an hour without loading up with gas.

 

[Don S]

Re: Thunderbolt IV

Check your fuel pump pressure.

 

[seada]

Re: Thunderbolt IV

The fuel pump is brand new and the engine still reacts the same. How could I adjust fuel pump pressure on a mechanical fuel pump? I will try anything at the point I am at.

 

[Bondo]

Re: Thunderbolt IV

I am running 4.3 v6 mercruiser with a thunderblot IV ignition system. The engine starts and runs great. It is timed 8 degrees before top dead center. Brand new rochester carb. Brand new fuel pump. Separate battery and wiring to accessories controlled by a blue sea battery switch. No water in fuel tank. Water seperator filter in-line from tank to carb. THE PROBLEM: timing will not advance. checked all wiring, new plugs, new wires, new coil. I thought i fixed the problem last year, but the last three times i went out it progressivly got worse. Now the boat won't go over 4 miles an hour without loading up with gas.

Ayuh,... Welcome Aboard,.... How'd ya Verify that,..??

 

[Don S]

Re: Thunderbolt IV

The fuel pump is brand new and the engine still reacts the same.

Didn't ask if it was old or new, I suggested you check the pressure. Wouldn't be the first new defective part installed.

Just curious, Did you buy the cheapest aftermarket marine pump you could find?

 

[Speakrdude]

Re: Thunderbolt IV

find my most recent post

 

[seada]

Re: Thunderbolt IV

I always buy OEM. I paid more for the fuel pump than I did for my first car.

 

[seada]

Re: Thunderbolt IV

I verified that I had no timing advance with a timing light.

 

[500dollar744ti]

Re: Thunderbolt IV

Where did you get the carb? Was it rebuilt?

 

[dubs283]

Re: Thunderbolt IV

did you install a new sensor in the distributor??

 

[PowerAddict]

Re: Thunderbolt IV

I always buy OEM. I paid more for the fuel pump than I did for my first car.

That's funny right there.

Did you check fuel pressure yet? Also, does your timing light have advance on it?

 

[seada]

Re: Thunderbolt IV

My timing light does have an advance on it. I bought the carb new from an outfit out of Florida I can not remember the name, I had to send them my old one they gave me a 100.00 credit. My next step is to change the sensor in the distributor. I did not check the fuel pressure yet. If and when I do check the fuel pressure how would I adjust it?

 

[Don S]

Re: Thunderbolt IV

My timing light does have an advance on it. I bought the carb new from an outfit out of Florida I can not remember the name, I had to send them my old one they gave me a 100.00 credit. My next step is to change the sensor in the distributor. I did not check the fuel pressure yet. If and when I do check the fuel pressure how would I adjust it?

Why replace that sensor, it has nothing to do with timing advance, neither does the carb.

 

[seada]

Re: Thunderbolt IV

The sensor in the distributor has nothing to do with timing advance?? What does?

 

[Don S]

Re: Thunderbolt IV

The ignition module. Where it's located on your engine, I have no idea. Probably mounted on the exhaust elbow.
Engine serial numbers are helpful here. Not every V6 is the same.

 

[achris]

Re: Thunderbolt IV

And depending on the year of the engine, it will be mounted either on the inside of the port exhaust elbow, or on the outside of the distributor... (it may look slightly different too)...

Chris.......

 

[seada]

Re: Thunderbolt IV

Thank you. Next question -- How do I determine if it is bad. What kind of reading should I be getting from this device? Or what should the input be??

 

[achris]

Re: Thunderbolt IV

Flash up the engine. Put the timing light on and see if the timing advances as the engine speed is increased. The module should have the total advance on it. The V6 maximum advance is 14 degrees at 2500 revs. This is not including the initial advance, so at 2500rpm you should see about 22 degrees (if the timing was set correctly at 8 BTDC at idle).

Chris......