Help with Thunderbolt ignition

[Francin728]

I have a 1998 5.0 mercruiser with a carb and alpha one drive. The issue I am coming across is identifying the type of thunderbolt ignition on the boat. The previous owner made various changes to the boat and I am trying to ensure I have the correct ignition setup. I am not getting the correct WOT RPM's and the motor does not seem to have the correct amount of power at it's maximum RPM. I have already gone through the fuel troubleshooting section and eliminated fuel/ant-syphon valve as the issue.

When I enter the serial number 0l023723 into the mercury parts catalog I am coming up with the ignition module on the exhaust manifold and an antiknock module attached to the ignition module. On the boat I only have the ignition module not the antiknock module. There is also no antiknock sensor just a threaded plug where the sensor. I have been informed that the serial number should be a thunderbolt v but the setup I have sounds more like a iv. Would someone please assist me with identifying the setup I should have and what I actually have?

I am wondering if the advanced ignition is being retarded under the miscalculation that there is engine knock and this is preventing me from reaching full power.

The engine actually starts and runs perfect minus the missing power at higher RPM's

 

[Bondo]

Re: Help with Thunderbolt ignition

I have a 1998 5.0 mercruiser with a carb and alpha one drive. The issue I am coming across is identifying the type of thunderbolt ignition on the boat. The previous owner made various changes to the boat and I am trying to ensure I have the correct ignition setup. I am not getting the correct WOT RPM's and the motor does not seem to have the correct amount of power at it's maximum RPM. I have already gone through the fuel troubleshooting section and eliminated fuel/ant-syphon valve as the issue.

When I enter the serial number 0l023723 into the mercury parts catalog I am coming up with the ignition module on the exhaust manifold and an antiknock module attached to the ignition module. On the boat I only have the ignition module not the antiknock module. There is also no antiknock sensor just a threaded plug where the sensor. I have been informed that the serial number should be a thunderbolt v but the setup I have sounds more like a iv. Would someone please assist me with identifying the setup I should have and what I actually have?

I am wondering if the advanced ignition is being retarded under the miscalculation that there is engine knock and this is preventing me from reaching full power.

The engine actually starts and runs perfect minus the missing power at higher RPM's

Ayuh,.... Yer motor Should have the T-Bolt V,... Not all of 'em use the knock sensor,...

Did you by-pass the timin' control, when checkin' the timin',..??
The control box oughta have identifin' text printed/ embossed on it,...

That said, I'd sooner think ya got Carb problems, over ignition issues,...

 

[Francin728]

Re: Help with Thunderbolt ignition

Ayuh,.... Yer motor Should have the T-Bolt V,... Not all of 'em use the knock sensor,...

Did you by-pass the timin' control, when checkin' the timin',..??
The control box oughta have identifin' text printed/ embossed on it,...

That said, I'd sooner think ya got Carb problems, over ignition issues,...

The ignition module just has a DENSO 131800-7071 sticker on it. Nothing else.

The carb was rebuilt two by two different rebuilders in an attempt to resolve the problem. I have pretty much rules out fuel but I am open to additional checks if you can think of any.

 

[Bt Doctur]

Re: Help with Thunderbolt ignition

could the module be for a V6 application and not V8?

 

[Bondo]

Re: Help with Thunderbolt ignition

The ignition module just has a DENSO 131800-7071 sticker on it. Nothing else.

The carb was rebuilt two by two different rebuilders in an attempt to resolve the problem. I have pretty much rules out fuel but I am open to additional checks if you can think of any.

Ayuh,.... What's the back story, How'd it get to this, Has it ever run Right for ya,..??

Does yer ignition match what ya found at Merc, other than no knock sensor,..??
btw, the lack of knock sensor won't retard the timin', quite the opposite would happen, it'd be No retard at detonation,...

 

[Francin728]

Re: Help with Thunderbolt ignition

The boat hasn't run right since I bought it. It starts fine and idles smoothly. Once you rev it up in gear it just doesn't have the power it should. I change the cap,rotors,and plugs annually. I am really stumped on this one.

 

[Bondo]

Re: Help with Thunderbolt ignition

The boat hasn't run right since I bought it. It starts fine and idles smoothly. Once you rev it up in gear it just doesn't have the power it should. I change the cap,rotors,and plugs annually. I am really stumped on this one.

Ayuh,.... Up in Don'S Adults Only section,... Click on #15,...

 

[acdc96]

Re: Help with Thunderbolt ignition

Just putting it out their... Could it be the prop? I know certain props could lower rpms.
Also, are your tests on the water? cause that could play a factor as well

Good luck

 

[Fun Times]

Re: Help with Thunderbolt ignition

Hi there Francin728!

5.0 Alpha's did not utilize a knock system, only the Bravo's. (See notes) 806611T MODULE, Knock Control (5.0L Bravo And 5.7 Alpha/Bravo)

Unfortunately we have to ignore the DENSO 131800-7071 as they pretty much all say the same for each engine model. Technically in a perfect world you should have a white sticker that Merc put on telling you the engine size and drive model used such as the one inside this next link. Your module should look and read like this one.
Mercruiser ICM Calib 5 0L Alpha | eBay and/or this one Mercruiser 5 0 Alpha Quicksilver ICM 861459T02 | eBay

Tell us the size/type prop you have and your stern drive gear ratio and your top RPM and boat speed and type of boat and are you trimming the drive up a little when on plane?

 

[Francin728]

Re: Help with Thunderbolt ignition

I am currently running a 19pitch 3 blade on a 1.47 alpha drive. This is the drive I received with the boat however it is the not the drive from the factory. It should have a 1.62 ratio. I have played around with with different props from 16 pitch 4 blades to the current prop I have not been able to get more than 36 mph. The boat is a 19 foot Donzi bowrider.

 

[MikDee]

Re: Help with Thunderbolt ignition

Once you get it fully warmed up, Then shut it down, and put the controls in forward, and at full throttle, then go to the engine, and see if the carb is opening fully? When warmed up, the choke should automatically be off also, wide open!

Next, go over your spark plug wiring, a small block chevy,,, Clockwise from 1-8-4-3-6-5-7-2 Facing the front of the engine, Right side 1-3-5-7, Left side 2-4-6-8, One crossed plug wire could really kill power.

 

[Bondo]

Re: Help with Thunderbolt ignition

Ayuh,.......

Here is a list of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

 

[achris]

Re: Help with Thunderbolt ignition

Check all cylinder compressions, then throw a timing light on the engine and check that the timing is advancing properly.

Chris.....

 

[Walt T]

Re: Help with Thunderbolt ignition

Do you boat in high altitude? Did you happen to see that missing plane up there?

 

[Fun Times]

Re: Help with Thunderbolt ignition

Do you boat in high altitude? Did you happen to see that missing plane up there?

I must say Walt, the sayings you come up with are pretty darn funny at times. Never know what to expect.:lol:

Get out of boating all together and hang out here teaming up with me giving wrong advice that sinks peoples boats n stuff

Lol, only you Walt, Only you.:watermelon: