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Jet Pumps / Re: more speed from 12jc 460 bbf stock internals
« on: March 25, 2015, 05:36:14 AM »
Thanks for all the helpful advice. Much more prepared for parker now! 👍
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Jet Pumps / Re: more speed from 12jc 460 bbf stock internals
« on: March 24, 2015, 07:47:29 PM »
Well just pulled off the water, fuel pressure was good @7psi . Timing was at 18° btdc. Once I corrected the timing and set it to 32° ish. Got me a top speed of 55 on the gps. Secondary working well and all linkages fully operating. Boat felt significantly faster and produced much more of a throaty sound. So with all that adjusted is that pretty much all I'm looking at for top speed? Now I'm thinking it must have a lower geared impeller. Was able to achieve 4600 rpm as compared to 4200 rpm .
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Jet Pumps / Re: more speed from 12jc 460 bbf stock internals
« on: March 24, 2015, 04:11:45 PM »
Yep I have a timing light that displays rpm as well so I can verify the tachometer on the boat. Gonna drop the boat in the pond here in an hour or so and I'll post my results . Gonna play with timing and record my new gps speed against current timing (unknown at moment) to proper timing ( 32-38°). Also gonna check my secondary on the carb at wot
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Jet Pumps / Re: more speed from 12jc 460 bbf stock internals
« on: March 24, 2015, 03:01:08 PM »
Here is the side view of the intake
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Jet Pumps / Re: more speed from 12jc 460 bbf stock internals
« on: March 24, 2015, 02:14:25 PM »
I'll get those pictures up soon, but as far as I know there is no type of ride plate or shoe to bite the intake water under the hull (new to jet pump terms, excuse my ignorance). But the engine is strong as ever. I'm gonna look and my set up and get some pictures up within the hour
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Jet Pumps / Impeller identification, how to?
« on: March 24, 2015, 10:26:17 AM »
How do I identify what impeller is I'm my 12jc berkley pump. Is there a way without removing the bowl??
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Jet Pumps / Re: more speed from 12jc 460 bbf stock internals
« on: March 24, 2015, 09:44:22 AM »
My guess was timing as well. The distributor is a hei with a vacume advance option but it isn't connected to the metering block on the carb like in a car or truck. Could connecting the vacume advice fix this issue? What timing should I look for at high rpm? Idle should be around 8-10 dbtdc on pump gas with stock compression if I'm not mistaken.
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Jet Pumps / Re: more speed from 12jc 460 bbf stock internals
« on: March 24, 2015, 09:08:01 AM »
Boats a 77 hallett bubble deck. Runs great fires right up has awesome power curve until top end and just feels slow compared to others. And 4200 rpm seems too low to me as well. Just rebuilt the holley 750 carb and tuned it with a vacu me gauge. Not sure where my timing is at the moment but it's set to start easily and not hard crank. Pump doesn't cavitate and place diverter works great. Not sure of the impeller in the pump but it is a 12jc berkley.
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Jet Pumps / more speed from 12jc 460 bbf stock internals
« on: March 24, 2015, 08:46:35 AM »
New to the forum have some questions about how I can get more top end from my 19' hallett. Has a 460bbf 750cfm holley hei ignition Stock internals with a 12jc berkley w/place diverter. Turning 4200 rpm @45 mph on the gps. Just seems like I should get more speed out of my set up. Any thoughts? Suggestions? ?
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