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Thread: 81 Cougar Jet restore - heading Twin Turbo

  1. #1

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    Feb 2019
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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"

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