SoCal Jet Boats
Tech Talk => Jet Pumps => Topic started by: NoRestraint on June 02, 2012, 07:32:10 PM
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Hi guys! So I didn't get to any of the work I wanted to over the past year because work has been slow. However it's picking up for the summer which means new parts :). Last year we all talked about messing with the secondaries and timing and cleaning the jets etc. I think I found the problem of why I can't get any faster on the water. I'm very poorly educated on engines and jet pumps but I found this chart on the PJB site,
http://www.jetboatperformance.biz/pages/calculator.html (http://www.jetboatperformance.biz/pages/calculator.html)
So while I'm trying to become familiar with motors and jets, here is my understanding from this chart, PLEASE CORRECT ME IF I'M WRONG. So I really have no clue which impeller I have but I'm guessing it's an A. For all I know, the motor is a stock 1986 454 which produces 230 HP. It has a Holley marine 715 CFM carb if that info helps at all. While looking at the chart on the PJB site I noticed that the correlation on the chart is 4000 RPMs, around 230 HP with an A impeller. So the way I am understanding this is that this is the highest my boat will perform with the current combination. I appreciate the feedback and any help you guys can offer. I'm trying to get this thing to run around 60-70 mph depending on financial circumstances. Thanks guys!
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Hi guys! So I didn't get to any of the work I wanted to over the past year because work has been slow. However it's picking up for the summer which means new parts :). Last year we all talked about messing with the secondaries and timing and cleaning the jets etc. I think I found the problem of why I can't get any faster on the water. I'm very poorly educated on engines and jet pumps but I found this chart on the PJB site,
http://www.jetboatperformance.biz/pages/calculator.html (http://www.jetboatperformance.biz/pages/calculator.html)
So while I'm trying to become familiar with motors and jets, here is my understanding from this chart, PLEASE CORRECT ME IF I'M WRONG. So I really have no clue which impeller I have but I'm guessing it's an A. For all I know, the motor is a stock 1986 454 which produces 230 HP. It has a Holley marine 715 CFM carb if that info helps at all. While looking at the chart on the PJB site I noticed that the correlation on the chart is 4000 RPMs, around 230 HP with an A impeller. So the way I am understanding this is that this is the highest my boat will perform with the current combination. I appreciate the feedback and any help you guys can offer. I'm trying to get this thing to run around 60-70 mph depending on financial circumstances. Thanks guys!
Unless the cam timing is retarded and there is no advance in the ignition timing, you should easily be in the mid 300's as far as HP.
Something is amiss....Never seen a big block that could not muster at least 4,400 RPM with an A impeller. :screwy:
A worn out 305 small block with an automotive camshaft, log exhaust and a Quadrajet can make over 230 HP ;)
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My worn the hell out 455 in my last boat with a berk and a tight A impeller pulled 5 grand (if i let it) all day long up until its last day on the water with only 7 firing. So somethin aint right bud
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Thanks guys. I guess its back to troubleshooting everything.
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And i think i have it at 12* btdc at idle
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And i think i have it at 12* btdc at idle
And with all do respect don't mean anything at all...What is the timing at 2500 RPM? :sly:
If your advance mechanism is not working properly, you could have 12* timing at WOT....BAM, you found your issue... ;)
GT
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And with all do respect don't mean anything at all...What is the timing at 2500 RPM? :sly:
If your advance mechanism is not working properly, you could have 12* timing at WOT....BAM, you found your issue... ;)
GT
x2 my 454 ran 4500 + rpm's all day "last year" dont know the Mph ...but pretty fast 8) shades required..
but this year...12* at idle and 12* at WOT ...wouldnt go very good at all....new dizzy and all better :thumbup:
and i hope im getting more than 230 HP :sly:
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And with all do respect don't mean anything at all...What is the timing at 2500 RPM? :sly:
If your advance mechanism is not working properly, you could have 12* timing at WOT....BAM, you found your issue... ;)
GT
i will try to check on that this week, ive got finals monday and tuesday so probably wednesday. I appreciate the help because i dont know where to start!
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i will try to check on that this week, ive got finals monday and tuesday so probably wednesday. I appreciate the help because i dont know where to start!
GT tells the truth. Total timing after advance rolls in is the only thing that matters. In fact, locked out timing even better, BUT can make the thing a little finicky to start.
The only other thing that is haunting my brain on this is the assumption it's an "A" impeller. Safe assumption normally on most boats, but this is an SST. One of the most modified and raced hulls out there, so I would be pulling the pump and disassembling just to make sure and KNOW what is in there. Could easily be that the pump is set up for the 700+ hp range at much higher rpm or varous combinations thereof.
Good news and bad news. Good news is, you have an SST, one of the most flexible and fun hulls out there! Bad news is, you have an SST, one of the most hot-rodded and raced hulls ever out there! ;)
Ray