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Thread: Engine of choice for jetboats???

  1. #1
    Daniel
    Hi again all!
    I will maybe get my stolen boat back. I bad shape but it is very hard to find a jetboat here in Sweden!
    I will change the engine in it because i guess that the old one is blown. It is also a stock Olds 403 & I've heard that it is better to use a BB chevy.
    Now to my question: Should I use a marine converted engine like mercruiser or is it just as good with a tuned or stock chevy 454 used in a car? I guess you don't need the same torque at low revs as in boats with sterndrive??
    Please help!!
    Brgds
    From a sunny sweden in late spring!
    Daniel

  2. #2
    Jungle Boy
    I will always go with a big cubic inch small block, if the boat don't weight too much.Theyw eight a couple of 100 lbs less and give you lots of room to work with.

  3. #3
    Daniel
    Thank you for the answer but how much power can you squeeze out from a smallblock and still keep it driveable for many years to come? Don't whant to rebuild the engine after each run... :-)
    Can I tune the engine the same way as it was ment to be in a car? Or is it something i should think about?
    /Daniel

  4. #4
    LeadFootTheRabbit
    Daniel, as for the torque numbers of a 403 Olds, you can get pretty close to the same if not better with a 350 or 400 chevy. I don't know about Sweden, but the availability of chevy parts is far greater than Olds parts in the U.S.. As for the big block, if you can get a 454 out of a car that will work fine. If your going to rebuild it, post up and let us know(year of car the motor is out of, length and weight of the boat, which pump and impeller you have and how you want to use the boat; family boating-vs-speed) and these guts will give you good information as to what you need. Good luck and have fun LDFTRBT

  5. #5
    LeadFootTheRabbit
    Read it again and see that you have a sterndrive. I'd use a small block. LDFTRBT

  6. #6
    Daniel
    I do not have a sterndrive!
    I have a berkley pump, don't know what model yet and I hope I can buy this boat from the insurance company.
    Just whant to know if I can tune a bigblock or a smallblock chevy the same as for car use or if I need to have another cam and /or carburetor setup?
    I guess i don't need the torque at low revs when using jet as a boat with a sterndrive would need...?
    /Daniel

  7. #7
    jordanpaulk
    Originally posted by Daniel:
    Just whant to know if I can tune a bigblock or a smallblock chevy the same as for car use or if I need to have another cam and /or carburetor setup?
    You are correct about changes in the power range. Generally in a jet boat you are cruising with rpms anywhere from 2500-3000 on up, depending on your addrenaline addiction. Iske makes some great marine cams that run on 114 degree lobe centers, designed for boats and higher rpm ranges. By advancing the lobe centers, the motor will still idle and the cam doesn't get big until you get further up in the rpm's.
    As far as carb's go, if you are running an engine with no cover, you can run a regular carb, such as a holley 4bbl. Just be ready to adjust the floats when the boat is in the water as it will sit different than when it is on the trailer.
    Hope that helped you out some.
    Jordy

  8. #8
    Jungle Boy
    I have a 383ci stroker that runs pump gas and hydraulic lifters with 450 hp and 440 ft/lbs torque. It is very driveable and requires little to none maintenence.The new 434ci motor (dart/merlin) that will be dynoed need Monday should come in with 535 + - HP and still run premium fuel. I'll post the dyno results after it is done. I am looking forward to seeing what I'll do.
    JB

  9. #9
    Jungle Boy
    Originally posted by Jungle Boy:
    I have a 383ci stroker that runs pump gas and hydraulic lifters with 450 hp and 440 ft/lbs torque. It is very driveable and requires little to none maintenence.The new 434ci motor (dart/merlin) that will be dynoed need Monday should come in with 535 + - HP and still run premium fuel. I'll post the dyno results after it is done. I am looking forward to seeing what I'll do.
    JB
    I guess I should proof read. Dynoed ON Monday and looking forward to seeing what it'll do.
    JB

  10. #10
    Hallett19
    Hey Daniel, do you know who the composer Ulf Bjorlin or Nadia Bjorlin are ??

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