4.3 tb IV no fire from coil

[Slimd11]

Bought the boat replace coil cap rotor button plugs she fired right up took it out wouldn’t go over 32 mph at 4000 rpms couldn’t get any higher rpm either come back in 2 days later she wnt start was reading 11.7 volts at coil and red and white wire coming from module on exhaust manifold put plug gap tester on end of coil got a few weak lights it started n went out wnt get spark or start

 

[achris]

Bought the boat, replace coil, cap, rotor button, plugs. It fired right up. Took it out, wouldn’t go over 32 mph at 4000 rpm, couldn’t get any higher rpm either. Come back in 2 days later it won't start. Was reading 11.7 volts at coil and red and white wire coming from module on exhaust manifold. Put plug gap tester on end of coil got a few weak lights. It started then went out. Won't get spark or start.

So, I've edited your post (in this reply) so it's a bit easier for others (and myself) to read and understand....

Have you run though the TB-IV troubleshooting flowchart?
If not, have a read of this post, which is a full description on how the system works, and at the end is the troubleshooting guide. Everything you need to know about the system and how to fix it is in there.

Thunderbolt Ignition systems.

Chris..........

 

[Slimd11]

Had some time to play around with the boat, I noticed my batt is only 12.5 volts the ignition is reading the same voltage but when I click it over to accessory it drops to 11.4 could the switch be the problem. Wait on my cuz extra hand to do the other test

 

[alldodge]

Need to clean some connections. Start with the battery cables at both ends including the grounds

 

[Bt Doctur]

sparkplug firing order correct?

 

[Slimd11]

Yes the firing order is correct , I replaced the coil and drove for a few hours. So I replaced the sensor inside the distributor cap still no fire, I check the red/ white lead from dist to ignition module and it’s only 11.7 volt!!!!! Would that be the ignition module

 

[Slimd11]

Sorry yes I cleaned the connections now I’m getting 12 volts at the coil still no fire

 

[alldodge]

Have you run though the TB-IV troubleshooting flowchart?

 

[Slimd11]

Thanks everybody I’ve figured out why it wasn’t getting fire. The safety or man overboard switch was erratic so I bypassed it temporarily and voila it started. Now I have to figure why I’m only hitting 4000 Rpms n 32 mph!!! I think mabe my carb isn’t opening up all the way? Idk never had a problem like this before I believe the 4.3 suppose to get up to 4800 rpm and 40 to 50 mph

 

[achris]

... I believe the 4.3 suppose to get up to 4800 rpm and 40 to 50 mph

A 4.3 in a 15 footer will go a lot faster than that, but in a 25 footer, a lot slower. The speed depends entirely on the propeller pitch. What you should be aiming for is between 4400 and 4800 (I prefer closer to the top than the bottom) at full noise. Forget what speed you're getting... Just aim for engine revs at WOT.

Chris.......

 

[Slimd11]

It’s a 20 ft so how do I check the engine revs? And what am I looking for

 

[Slimd11]

Mabe the pitch is too low because she shoot right out up on a plane also have tabs on the back

 

[MichaelBC]

It’s a 20 ft so how do I check the engine revs? And what am I looking for

Put your boat on the water
Start the engine
Let it warm up a little
Check that the area in front of you is clear
Open throttle all the way
Wait for 10 seconds
Take a look at the tachometer and see what it shows ....

If it shows 4600-4800 your prop is good
If you don't reach the 4600 your pitch is too high
If you are reaching above 4800 your pitch is too low.

This depends on many things and there is no other way than just try.

Last year I took a selection of propellers with me on my holiday trip and tried them all, but still have not found the perfect one for me.

 

[achris]

Mabe the pitch is too low because she shoot right out up on a plane also have tabs on the back

Tell us EXACTLY what prop you're running. Make, model, style, number of blades, diameter (in inches) and (most importantly) pitch (also in inches). And if it's one with vent holes at the root of the blades, sometimes called PVS, tell us that too, and what size the holes are.

And when you're doing the revs check, make sure the tabs are fully retracted! And go down and check them visually!

Chris.......

 

[Slimd11]

Looked at prop it has a 21 p shall I try a 18 or 19 p

 

[Slimd11]

It’s a quicksilver 48 16546 A40 21p

 

[Slimd11]

Quick silver laser 2 yes it has vents and 3 blades tabs are manual

 

[Slimd11]

Here’s prop

 

[Slimd11]

Here’s numbers

 

[achris]

Mabe the pitch is too low because she shoot right out up on a plane also have tabs on the back

See those vent holes? They are why you' 'shoot right out up on the plane'...

Your engine is a 4.3, so it could have a 1.84 or a 1.62 drive ratio. If it's 1.62, then that prop has too much pitch. My 20' with a 4.3MPI (with a 1.62 drive) runs 17 or 19 (depending on the day), but when I had the 4.3LX (with a 1.84 drive) I was running a 21...

So, what's your drive ratio?

Chris.