Hesitation, 5.7 mercruiser w/thunderbolt ignition

[1988invadar]

Hi

Less than ten year old Larson boat.

We have replaced everything but the thunderbolt ign module at this point.

plugs
cap
rotor
wires
ignition sensor
coil

We have cleaned the carburator, have not rebuilt it.

After replacing the ignition sensor starts harder than before replacement.

Problem before replacing parts can't get out of the hole when applying full throttle. Unable to ski and tube behind.

Any help would be appreciated.

 

[Haut Medoc]

Re: Hesitation, 5.7 mercruiser w/thunderbolt ignition

You do not say what type of Tbolt you have......IV or V.......
The V is a different process to time.....
Ign modules either work or they don't.....
Your problem is more likely to be your accelerator pump.....
Pull the flame arrestor off & pump the throttle....
You should see two good streams of fuel squirt into the throat of the carb.....
If not, you will need to rebuild at least the acc pump......​

 

[1988invadar]

Re: Hesitation, 5.7 mercruiser w/thunderbolt ignition

Thanks for the response Haut

Got good gas does not seem to be the issue believe the module may be a V and we're using a IV book that covers boats thru 1988 his larson is younger than my Invader so I would assume that the ignition is a V.

One more thing, when the motor heats up the condition gets worse. It seems to me that he has an electrical failure about to happen. Parts get hot they break down or start to resist more. He just hasn't reached critical mass yet. I fear the Ignition module is the problem but want to be sure before he makes that expence or he drags it to the dealer and sells his soul.

Dealers keep telling him it's the prop but that's stock.

thanks again

 

[Haut Medoc]

Re: Hesitation, 5.7 mercruiser w/thunderbolt ignition

You need to post the serial # or at least the year of the engine.......
Does "good gas" mean that you have visually verified that the accelerator pump is indeed working?.......​

 

[1988invadar]

Re: Hesitation, 5.7 mercruiser w/thunderbolt ignition

Haut

I'll have to get back to you on the year s/n unavailable I and the owner are separated by many miles from boat. I will Email owner he will be able to provide year at least.

The gas is running to and into carb with no problem rule out both pumps and/or clogged filter. fuel is fresh.

Will reply after I hear back from him.

Thanks again

 

[Haut Medoc]

Re: Hesitation, 5.7 mercruiser w/thunderbolt ignition

Haut

I'll have to get back to you on the year s/n unavailable I and the owner are separated by many miles from boat. I will Email owner he will be able to provide year at least.

The gas is running to and into carb with no problem rule out both pumps and/or clogged filter. fuel is fresh.

Will reply after I hear back from him.

Thanks again

You still have not answered the most important question....

Does "good gas" mean that you have visually verified that the accelerator pump is indeed working?.......
The fact that gas is getting to the carb is irrelevant at this point as the engine will run.....
If you do not see those two streams when the thottle is pushed, then that is your hesitation problem......
I can't put it any plainer than that.....

 

[1988invadar]

Re: Hesitation, 5.7 mercruiser w/thunderbolt ignition

Haut

YES! the gas is running in streams when the throttle is pushed = good gas.

Thanks

 

[Haut Medoc]

Re: Hesitation, 5.7 mercruiser w/thunderbolt ignition

Read this post.....
http://forums.iboats.com/showthread.php?t=204699&highlight=shunt​