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Thread: Olds / Berkeley setup question again

  1. #1
    painterdan32
    I have what could be called a new 18' 1972 Sidewinder jet boat. The pump is a 12-JC A impeller. All new rebuild ( done myself last winter). The engine is a 455 bored .060 over ( Marshall Marine rebuilt longblock). Factory intake, Holley Marine 750 dual feed carb 9015 model (not doubble pumper). jets are currently 73's in front and stock whatever in rear bowl. That has a funny looking screw in it to remove the metering . So I left it alone. HEI distributor with an MSD processor in it for rev limiting. Log exhaust. Place hydraulic diverter. I believe the loader is an SS loader. It is the smaller loader for lower horsepower engines. I dont see any hook in the hull when I check it. The bunk boards exit the rear of the boat when it is on the trailer and I have no cavitation or porpise in it. the only problem I'm having is that I cant get the boat over 4000 RPM. At 4000 rpm though it running somewhere between 55 and 62 MPH ( guessing without GPS). It's got plenty of throttle left. I've got about 20 degrees of throttle throw left. the extra throttle just doesnt get it anywhere as far as performance pickup. I only use that part of the throttle to kick the secondaries in. My question is this. At which end do I look for the performance? Impeller or engine. I don't know what a jet should do as far as the overall performance power band, but this thing will rip right out of the hole. Last year the jet was so sluggish we would have to run about 3000 rpm to get enough movement out of the boat on the lake to move through rougher water. This year we can maneuver to a channel at 1500-1800 rpm. We just cant get to 4500 where I'd like to be. Any thoughts?

  2. #2
    DelawareDave
    The screws that hold the metering plate to the carb body are called "clutch head" screws.
    You have an Olds, so you may not want to run it over 4000 for very long anyway, unless you have oil restrictors and drainbacks installed. Your impellor may be why you can't spin it up any faster. I don't remember right off hand, but you may need a smaller impellor.

  3. #3
    painterdan32
    The screws that hold the metering plate to the carb body are called "clutch head" screws.
    You have an Olds, so you may not want to run it over 4000 for very long anyway, unless you have oil restrictors and drainbacks installed. Your impellor may be why you can't spin it up any faster. I don't remember right off hand, but you may need a smaller impellor.
    I've looked at the chart (impeller vs. horsepower) and it confuses me. Hell, I even turned it over for clarity. One thing I dont understand is why an A impeller is stock if it won't turn a "stock" motor. By the way, extra large oil pan and restrictors. I never run below 50 psi on oil. Read all about that this winter. Forgot to mention the bowl stuffer too. Yeah, thats the name of the screw. I just couldn't remember what they were called. Usually in the auto collision industry they will use a stupid fastener to warn idiots not to mess with stuff. (tamper proof torx in the airbag system ect.) Being the bodyman/ painter I am, I'll leave the technical mechanical stuff to someone else.

  4. #4
    DelawareDave
    The curve is an approximation of horsepower/RPMs/impellor size. According to the chart, you are producing a little over 200 horses. Kinda low for that engine, I would think. You may need to raise the diverter to get the nose of the boat out of the water.

  5. #5
    Old Guy
    Quite a bit of this needs clarity. Did Marshall Marine give you any indication as to probable hp of this motor? Any experienced engine builder should be able to predict approx. hp if all the components are defined. Things like carb size and jetting, fuel supply, ignition timing, and the exhaust system will effect the available hp of the finished motor.
    I don't know much about carbs, but I'm running a 930 cfm double pumper on my Olds (.030 over dynos 470 hp). The 750 might be a bit small.
    I doubt if 200 hp will get your Sidewinder to go 60 mph. I had a Sidewinder (looked just like yours) for about 10 years. I tinkered with it a lot. I really liked the boat, but I did not like the seating arrangement.
    If your A impeller is an Aggressor A impeller, it is equal to a Berkley AA impeller. If you are looking at the Berkley chart, then you need to be looking at the curve for a AA impeller.
    Without knowing what should be expected, it's hard to guess if anything is not right.
    Is the tach reading correct? What is your actual mph?
    Can't make a proper comment without more info.
    old

  6. #6
    painterdan32
    Quite a bit of this needs clarity. Did Marshall Marine give you any indication as to probable hp of this motor? Any experienced engine builder should be able to predict approx. hp if all the components are defined. Things like carb size and jetting, fuel supply, ignition timing, and the exhaust system will effect the available hp of the finished motor.
    I don't know much about carbs, but I'm running a 930 cfm double pumper on my Olds (.030 over dynos 470 hp). The 750 might be a bit small.
    I doubt if 200 hp will get your Sidewinder to go 60 mph. I had a Sidewinder (looked just like yours) for about 10 years. I tinkered with it a lot. I really liked the boat, but I did not like the seating arrangement.
    If your A impeller is an Aggressor A impeller, it is equal to a Berkley AA impeller. If you are looking at the Berkley chart, then you need to be looking at the curve for a AA impeller.
    Without knowing what should be expected, it's hard to guess if anything is not right.
    Is the tach reading correct? What is your actual mph?
    Can't make a proper comment without more info.
    old
    Thanks for the feedback old. You helped me a ton this winter with my cooling problems and it is perfect now. The tach is correct according to the test instruments the mechanic had plugged in the first time out. As far as an actual MPH, That is unsure at best. The speedo doesnt start to pickup untill I start to plane out. At 4000 rpm it reads 53 to 55. It needs a new line put in it. Fuel supply is a 3/8 hose to the mechanical pump, -6 to the carb. Initial timming is set at 12 BTDC. Berkeley log exhaust. The block is stamped to be a Toronado engine originally. All the pump parts are Berkeley from CP Performance. If you say I'm only getting 200 HP, then I'm reading the chart correctly. I should be around 350 I believe. My vacum advance is working fine as far as I can tell, but I dont know if I should be running advance due to other threads. I admit to limited mechanical abilities. Afterall, I'm a body guy.

  7. #7
    Old Guy
    If you PM me, I'll try to stay with you on this. I gotta a lot goin on right now.
    Most boats don't use vac. advance on dist. At WOT, there is not much vac. so you can't be sure what you are getting. Better to get rid of it and go for 34° - 36° total all in at about 3K rpm. Mine is locked at 36°, but my motor is a bit different from yours.
    old

  8. #8
    HotDogz
    You may want to address the "factory intake" as well. Is that the stock quadrajet intake with turkey baster tray? If this is the case, replace it with an Edelbrock at least.
    And ditch the HEI unit and get a distributor that will allow you to customize your timing curve.
    You should be able to spin your motor to at least 4500rpm with a Berk "A" impeller or equivalent.

  9. #9
    Old Guy
    I agree with HotDogz. If you're going to run a log type exhaust system, I recommend an Edelbrock Performer intake manifold. I've seen some used ones priced very reasonable. An MSD ignition update would be nice if your budget can handle it.
    old

  10. #10
    painterdan32
    You may want to address the "factory intake" as well. Is that the stock quadrajet intake with turkey baster tray? If this is the case, replace it with an Edelbrock at least.
    And ditch the HEI unit and get a distributor that will allow you to customize your timing curve.
    You should be able to spin your motor to at least 4500rpm with a Berk "A" impeller or equivalent.
    Quadraket intake yes. Turkey baster? You got me on that one. Is there really that much difference? If thats so, That sounds like a winter project when I'm not buying fuel.

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