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Thread: 81 Cougar Jet restore - heading Twin Turbo

  1. #1

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    81 Cougar Jet restore - heading Twin Turbo

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    So I bought a 21' Cougar jet (cdn) and am in the process of re-powering it. It has a basic 12JG pump with a bronze A3 and electric jetovator. The original Gen IV 454 is semi-seized from sitting, I took one head off - its rusty so a complete rebuild would be required. I can move crank 1/4 rotation.

    I have run carb motors in cars/trucks etc, but I wanted a FI motor in the boat, I found a local 8.1L Mercruiser base engine\ecu (Gen VII) that turns over, has some hours but ran when removed (he said). I paid $750 for the core and thought I would run it a season and see. Of course I cant leave stuff together unknowing for long so I pulled the FI and flushed out bad gas, pulled intake, found loose injector parts in intake tracts and before long its a shortblock. Heads looked reasonably good, lapped valves, threadlocked studs in ( a bit loose) and put them aside for later. Cleaned pistons and found one with small detonation pits or ??, minor wear on cylinders. There are Hypereutic which I dislike but there are .005 over forged pistons that can be hone fit so thats it, sorted.

    A vac trip to San Diego and a new roller cam and rockers came home. All upgrades easily handled by the stock ecu with a bit of fuel pressure increase. Reprogramming a Mercury ecu for me is mail order and expensive and who knows how good.

    And along comes Seattle boat show.

    Met a guy there who was local and ended up buying an old school Banks TT setup, complete, shiny, hardly used, it followed me home.

    It all fits nicely inside the doghouse and should make a lovely sleeper or maybe just and explosion who knows.

    I have a custom NA boat cam 242/249 @.635/.649 LSA 116 and 13 deg overlap, I could trade this in on two different forced induction cams they make but I dont know if either is better Turbo suited, they sell for Whipple charged engines, I will attempt to get timing cards for them. I have a Holley HP ecu and wiring harness to deal with the tuning aspect of this.

    Anyone got any thoughts?

    How do most tune wet exhaust engines? on water?, anyone know of wet-dynos in Pacific NW area.

    I know this all looks kinda hair-brained, but its a hobbly and it just happens when pieces became available and they are suitable for the era of boat I think.

  2. #2

    Re: 81 Cougar Jet restore - heading Twin Turbo

    No it's not at all. Some very good insight, for the do it yourselfer, can be found on these videos here:

    Alexi is a master with the Merc. ECU's. there are a number of people doing similar work. the only real hurdle, is to install the o2 sensor, in a dry section of exhaust, like right at the turbo exhaust outlet. love the build by the way.
    It's Impossible to Lose Your Footing, If Your On Your Knees"

  3. #3

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    Re: 81 Cougar Jet restore - heading Twin Turbo

    Its getting too close to spring, I think the boat is gonna get a SBC carb motor for a while. I had built it for my kids truck nut he is away militarily so its just sitting and I need a power source so it will move thru the water while I sort out (spend $$) to finish the big block that it should have. Time is a factor for me now. It ran very well in his truck but I know its too small to turn the A3 impeller, probably have to get a used A or B or something. Its a 10:1 350 with ported and smoothed Dart heads. Too high of compression to throw on the Banks setup for fun.

    It has a solid roller cam with about 25deg overlap....is that too much and be a water reversion problem? It idles nice, too nice for a hotrod really, just the sewing machine sound of the lifters and rockers to make it sound non-oem.

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  5. #4
    Team Dirt Bag Intern NUTTZ
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    Re: 81 Cougar Jet restore - heading Twin Turbo

    What exhaust paired with your set up? That is where to start for the small and big block! Your pump does what it says it pumps a lot of water and reversion is always something to think about. Nothing wrong with the small block vs big block except torque, you want it
    Heavy Lake Lay Up Family Boat Ready To Race Any Takers

  6. #5

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    Re: 81 Cougar Jet restore - heading Twin Turbo

    I have 3-1/2" thru hull wet exhaust. I have two sets of BBC logs and snails. no sbc logs yet. Picked up a Dominator bowl today to replace my dinged up Berk JG, I think its a bolt on.

  7. #6

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    Re: 81 Cougar Jet restore - heading Twin Turbo

    Tahiti: Why put the O2 sensor at the turbo outlet versus say the turbo inlet, is exhaust pressure a factor? Seems very close to water, mist. (6" to wet hose)

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