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  1. #1
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    Default Thunderbolt IV replacement

    Can anyone tell me the replacement amplifier for this Thunderbolt IV (See pic). I want to have a back-up as this one is getting long in the tooth..It's on an AQ260A, btw..
    Many thanks!
    Mike

    Click image for larger version. 

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  2. #2
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    Northboro, Ma, USA
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    Default Re: Thunderbolt IV replacement

    What engine size?

    V6, V8 (305 350) and V8 (454) all use different timing control modules.

  3. #3
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    Default Re: Thunderbolt IV replacement

    Sorry, the 260 is a SBC 350, with a total timing advance of 30..
    thanks, kghost

  4. #4
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    Default Re: Thunderbolt IV replacement

    In my opinion I would not spend the money for a "spare".

    A new one from this site or any marine retailer will be around $400.00 +/-

    What year is the boat?

    The timing advance ~ 22* for the module........so that would be 8* of initial timing on the motor.

    Look on this site for a replacement and get the part number and do a ebay or google search for a replacement.

    The newer modules are very small comapired to the one you (and I have) on the boat. Different package same connections and the same result.

  5. #5
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    Default Re: Thunderbolt IV replacement

    The boat is an 81 Anacapri, but repowered it about 2 years ago with the same V8. It has a 280 Drive with the TB IV ignition. I love that Thunderbolt system, and wanted to have another ready when/if this one wears out…I guess my question is which one to buy. I see modules with the 22 advance, but different part #'s, etc. Just want to make sure I get the correct one. I'll look around again, but for some reason just can't seem to find the one I'm looking for. Thanks, kghost...

  6. #6
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    Default Re: Thunderbolt IV replacement

    It appears based on the year chart on this web site that in 1981 they were still running point ignitions. so your boat could have been a late model year manufactured date and received the TBIV ignition. Or it was upgraded at some point............
    So I would say any 350 V8 timing module from 1982 - 1986 would work fine.

    The one for your motor appears to be part # 15248T02 and costs ~ $430-450 new. about 1/2 on ebay (1982-1986

    The one that supersedes that (1987) and is the same is but is smaller and requires the cable as shown in the picture and comes with it I believe

    http://www.marineengine.com/newparts...um=MER15899A+1

    and costs the same new...........

  7. #7
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    Default Re: Thunderbolt IV replacement

    Thanks, kghost..Perfect. Out of curiosity, you mentioned that you are running that same old module that I am using. Any concerns about it giving out, and if so, would you just swap with a new one, or just run until it gives up the ghost. (sorry..couldn't help myself).
    Mike

  8. #8
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    Default Re: Thunderbolt IV replacement

    I have no concerns what so ever and my boat is a 1987. If it does it does.....I don't use my boat on salt water so shore is never far away.

    Besides I have a few spare parts from being in the business.................lol

    I have timing modules for four different spare ones, one big block V8 and two small block V8's (one original like yours and one newer style) and one for a v6 and one for a 4 cylinder.......I used to do a lot of repairs.......now only help friends.....

    One for the big block and has a couple more degrees advance..........

  9. #9
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    Default Re: Thunderbolt IV replacement

    Got it..Ok.
    Thanks for the support. Might ask again for something else...
    Best,
    Mike

  10. #10
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    Default Re: Thunderbolt IV replacement

    Quote Originally Posted by jaegerboy View Post
    Sorry, the 260 is a SBC 350, with a total timing advance of 30..
    You are correct about the AQ260... but incorrect about the AQ260 TA being 30 degrees..... unless an alternate build had been done.

    That TB is a Merc product, and it's a EST system.
    I'd ditch that, and install a YLM624AV, and not look back.


    BASE is BASE all day long. We fire up on it.... and we idle on it.... and that's about it.
    Pay much more attention to your Progressive and TA.

    With either system, set your BASE advance so that your TA is correct at/near 3.2K RPM.


    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  11. #11
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    Default Re: Thunderbolt IV replacement

    Rick,

    I've been reading you for a long time, and would never doubt you, so please know that's not what I'm doing..And have read you tout the YLM624AV for the 260 before..

    But from my 260 manual:

    260HP
    4400 rpm max
    8.5:1 compression
    142-156 psi compression at cranking speed
    8 cylinder
    3.9995"-4.0025" clinder bore
    0.002" max out of round
    3.480" stroke
    350 cubic inch
    893 lbs. weight with 280drive
    600-650 rpms idle speed
    clockwise rotation(seen from front)
    91 octane (ron)
    6-8 psi fuel pressure
    Rochester 4ME carb
    38A alternator output
    1.3hp starter motor
    Bosch HR8A spark plug
    .028" plug gap
    1-8-4-3-6-5-7-2 firing order
    8 degrees BTDC idle timing
    30 degrees @4200 rpms full advance
    .014"-.019" point gap
    28 degrees - 34 degrees cam angle
    143 degrees t-stat starts to open
    160degrees t-stat fully open

    I have looked at replacing that TB IV with your
    recommend, but am so darn happy with it…
    Am i looking at this incorrectly?
    Mike

  12. #12
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    Default Re: Thunderbolt IV replacement

    Quote Originally Posted by RicardoMarine View Post
    You are correct about the AQ260... but incorrect about the AQ260 TA being 30 degrees..... unless an alternate build had been done.
    .
    See earlier post.................."22 advance for the module + 8 for initial"............

    As far as a replacement distributor Rick is correct and many have gone that route.

    The motor does not care what ignition it has as long as it works as designed and for your application.

    The benifit of the YLM distributor is it has no external parts other than the coil. It is a very good replacement.

    If you were to purchase all the parts for the TBIV, 1 rotor, 1 sensor, 1 timing module all new from a merc dealer, you could purchase two (2) brand new YLM's.........

  13. #13
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    Default Re: Thunderbolt IV replacement

    Ok, got it..Thank you both!
    Mike

  14. #14
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    Default Re: Thunderbolt IV replacement

    Quote Originally Posted by jaegerboy View Post
    Rick,

    I've been reading you for a long time, and would never doubt you, so please know that's not what I'm doing..And have read you tout the YLM624AV for the 260 before..

    But from my 260 manual:

    clockwise rotation(seen from front)
    91 octane (ron)
    6-8 psi fuel pressure
    Rochester 4ME carb
    38A alternator output
    1.3hp starter motor
    Bosch HR8A spark plug
    .028" plug gap
    1-8-4-3-6-5-7-2 firing order
    8 degrees BTDC idle timing
    30 degrees @4200 rpms full advance
    .014"-.019" point gap
    28 degrees - 34 degrees cam angle
    143 degrees t-stat starts to open
    160degrees t-stat fully open

    I have looked at replacing that TB IV with your
    recommend, but am so darn happy with it…
    Am i looking at this incorrectly?
    Mike
    Mike, that is entirely up to you! You need to be happy!

    FYI:
    The thunderbolt system is EST (electronic spark timing). Via electronic circuitry and via the algorithm from the module, the spark event is delayed..... and the delay is then manipulated as per RPM.

    It also uses photo-eye triggering! Photo-eye is very accurate...... but we're dead in the water if the infra-red unit fails.


    The YLM is not EST! Is uses VR triggering.
    VR (variable reluctor) is tried and proven.


    **********
    All AQ series engines are CCW (aka standard LH rotation)! (Viewed from flywheel end)

    You are showing a TA of 30 @ 4.2k rpm. The more important TA will occur @ 3.2k.

    143* stat for raw water use in ocean water....... 160* stat for fresh water or Closed Cooling system!


    .
    Last edited by RicardoMarine; 05-06-2014 at 10:20 AM.
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  15. #15
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    Default Re: Thunderbolt IV replacement

    Thank you, Rick..
    I do greatly appreciate your responses and value all your advice...
    1 more question than. What is the procedure for swapping the TBIV to the YLM?
    Oh, and I do use a 160* thermostat here in Southern California. No good you say? Getting too much salt you with the heat you think?

  16. #16
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    Default Re: Thunderbolt IV replacement

    If you change ignition systems… bring the crankshaft around to #1 cylinder TDC and on the compression stroke.
    Actually… stop the crankshaft at about 6 prior to TDC!
    Now you will be able to remove the old and install the new, and do your cap, rotor and spark plug wire indexing.
    You will be adjusting the position of the distributor housing with the ignition excited (more on that if need be)!


    Salt begins to crystallize at around 145. Layers of salt crystallization can hinder engine cooling.
    If your engine is raw water cooled and you are running in the ocean, you will want to run the 143 stat.
    If you run in river or lake water, or have a close cooling system, the 160 stat maintains a better engine temperature.


    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  17. #17
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    Island Heights, NJ,
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    Default Re: Thunderbolt IV replacement

    In so far as getting a spare... Spares are warranted for parts with a known or demonstrated wear mechanism leading to failure. The Thunderboat IV has no "wear parts". A better spare philosophy would be a cap and rotor ( both sealed in a plastic bag!).
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280

  18. #18
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    Default Re: Thunderbolt IV replacement

    Thanks, Capt Bob..
    Understood. And do have an extra cap, rotor and sensor for this TBIV as well..Very good points and I do appreciate it as always..
    I have the same power and drive as you, from the looks of it. (Just need to get the duo prop and I'd be very happy..)
    Cheers..
    Mike

  19. #19
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    Default Re: Thunderbolt IV replacement

    Quote Originally Posted by sandkicker View Post
    In so far as getting a spare... Spares are warranted for parts with a known or demonstrated wear mechanism leading to failure. The Thunderboat IV has no "wear parts". A better spare philosophy would be a cap and rotor ( both sealed in a plastic bag!).
    IMO, any ignition part that can fail, and can be replaced on the water....., is worthy of having a spare on board.



    Quote Originally Posted by jaegerboy View Post
    I have the same power and drive as you, from the looks of it. (Just need to get the duo prop and I'd be very happy..)
    Mike, you would be very pleased with the Duo Prop lower unit behind your AQ260A.


    .
    Rick ... aka Ricardo..... AQ series Volvo Penta repair
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP drives

    "Intellectual growth should commence at birth and cease only at death." Albert Einstein

    Please... no PMs! Post your questions on the forum.

  20. #20
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    Default Re: Thunderbolt IV replacement

    too bad I don't live in Portland anymore..I'd be seeing you quite a bit, I think Rick..Love to have you take care of that for me..

  21. #21
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    Default Re: Thunderbolt IV replacement

    Rick,

    Just for grins, wanted to let you know that I purchased a DPC-1 lower and installed onto my 280.
    It will be in the water in a month or 2..Looking forward to seeing what this boat will do with it..
    Once again, your advice is invaluable.
    Cheers,
    Mike J.

  22. #22
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    Default Re: Thunderbolt IV replacement

    I have a good box available, pm me

  23. #23
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    Default Re: Thunderbolt IV replacement

    Is this for the TBIV? If so, already taken care of but thanks Bt!

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