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Thread: Finally!!!, but it bust loose on me

  1. #1
    Hallett of a Dream
    Well, I finally found and purchased my childhood dream, a jet boat. It's a 1976 Hallett with a 455 Olds and of course the Berkeley 12JC-A. Well, I took it for a test drive and everything seemed great. I could get 5200rmp out of the motor, stamp out about 62mph. The oil was changed in it before I bought it. The motor was supposed to have 108 hours on it, great, pretty new, right??? Guess not. After the second day of running it, I had to add over 1 qt of oil. By the end of the third day, she was knocking bad. It came on all of a sudden. Everything was fine, headed back to the ramp, running a steady 4300rpm, tried to get on it, but it wouldn't. Let off the throttle, knock knock.....uh oh. Spun the #7 and 8 rod bearings. the oil was black as coal. I only put 8 hours on the damn thing, now I am looking for a new motor. She handles like a dream and looks and sounds great, well, when it runs. Now I am looking to do things right the first time, over. any suggestions????? Yes, the first thing I did was cut the stops off of the Jetovator, but the damn brass tooth gear is seroiusly worn. HELP!!!!!

  2. #2
    RiverToysJas
    The two happiest days of a man's life are the day he buys his boat and the day he sells it. We all have stories just like this and if you don't, you haven't owned a boat long enough. If you're handy with motors, you can rebuild that thing w/o too much trouble. If you're not handy with a wrench, you will be soon enough. If you don't believe me, ask to see the tools that us 70s squirt boaters carry on board - I can rebuild the motor right on the river these days!
    G'luck!!!!
    RTJas.

  3. #3
    riverlover
    My suggestion, and I'm no expert, is to pick up a couple cases of bullets and start hunting around for buddies that like to rebuild motors. You might even find a helping hand here. Sorry, I can only offer moral support because I'm a newbie when it comes to motors.

  4. #4
    Hallett of a Dream
    I guess what I'm comtemplating here is it a good idea to buy a rebuilt marine motor, long block for $1200 and go from there? I do know motors, inside and out, but when it comes to marines, one guy tells me you can't take one out of a car and swap it in, and the other tells me that the cams are different between cars and marines. I find that hard to believe. I do believe the head gaskets are different though. I am about 5 hours from Detroit and there is a supplier that has my engine. should I make the trip?

  5. #5
    Heatseeker
    BOAT:
    Break
    Out
    Another
    Thousand
    I have a bud that pulled a 455 out of an old Vista Cruiser wagon. The engine had 100k plus miles on it. He put it in his jet and it ran fine. That was 4 years ago and it still runs tits.
    [This message has been edited by Heatseeker (edited September 01, 2001).]

  6. #6
    riverlover
    I met a guy at the river a few years back that told me he got a 454BBC at a junkyard. He said he went through it, freshened it up, painted it, bolted on some chrome stuff and stuck it in his boat. It ran as strong as any other boat I saw on the water. BTW, he didn't mention any special marine mods.
    I'm sure someone more knowledgable about this subject will chime in by Tuesday (big weekend here)RL

  7. #7
    jetboatjake
    IMHO Now would be the time to think about getting away from the olds.I am no expert by any means. From what I read the chevy valve train and top end is much more dependable and also hase a better oiling sys and bottom end. I also believe the are tons more after market mods available.Drop a comment here on what your budget is and you will get tons of input.Couple cases of bullits and a rebuild would be cheapest or just pick up a crate motor.Or Call my engine guys here in illinois they are building big cube dominator chevys way dependable and big torque and HP numbers.I can help getting it out to you also.

  8. #8
    Hallett of a Dream
    Well, the budget isn't weak, but I can't have a Summit truck here every week without the wife having a cow and wanting another new car. As far as the big weekend goes, I have to take our other boat, a 17' open bow 85 horse outboard. But hey, it floats, it runs and burns up gas. Better than nothing I guess, but not quite the jet is it?

  9. #9
    Havasu Hangin'
    Originally posted by Hallett of a Dream:
    I guess what I'm comtemplating here...one guy tells me you can't take one out of a car and swap it in, and the other tells me that the cams are different between cars and marines.
    Mercury buys its marine engines from GM's truck division. Since there is no gearbox or coasting in a boat, marine engines are constantly under load, unlike a car. Therefore, the engine is similar to a truck engine- build torque fast, and use beefy forged parts.
    The main difference between a car and a boat engine is brass freeze plugs.
    The cam grind may be a little diiferent, only in that it has to build bottom end torque, and not allow reversion (water getting sucked back in). This comes into play for larger cams, not the milder ones. When looking for a cam, if you stay with a cam that has a Lobe Separation Angle above 110 degrees, and an Intake Lobe Centerline in this area, with not too much duration, you should be fine. http://www.goldenplasma.f2s.com/foru...es/happy04.gif
    If it were me (and believe me, you don't want to be me) buying that short block, I would make sure I got a forged crank and pistons, good rods, and make sure it is align bored, deck plated, and balanced. I'm sure you don't want to go through this again in a couple years. http://www.goldenplasma.f2s.com/forum/smilies/sad03.gif
    Uh...my bad...wrong forum...sorry guys.
    http://www.goldenplasma.f2s.com/foru...es/happy25.gif

  10. #10
    Hallett of a Dream
    I think what I'm going to do it just buy a used engine, replace all the gaskets , including the head gaskets and run it until I get my other engine built the way it should be...beefy and horsed. At least that will get me running again.

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