Why am I too slow?
10-01-2006, 01:06 AM
#21
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Re: Why am I too slow?
I got a 11 mph increase in my donzi 25 with 454 mag. Changes i made is as follows. CMI stainless headers. Mirage plus 21 to Bravo 1 22. I think 4-5 mph here. Sanded all the bottom paint off. Worst horrable job in the world, I would rather clean a **** truck with a tooth brush. Anyway, after a coat of Perfection under coat and top coat we got a total of 11 MPH. I was astounded at this and put almost all of to the bottom paint
10-01-2006, 11:00 AM
#22
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Re: Why am I too slow?
Originally Posted by Mike Paula
I am using a 502 GM performance Short block.The Heads are the same as a zz502. I would have thought I would pull more RPMs than it does. I have a flowed 600 holley with the same jetting as the stock zz 502(dont have spec here with me).
750 would be better but still a little too small.
Get a 800-850 Holley or BG 850 if you want to let it breathe.
A 600 is made for mild 5.7's.
10-01-2006, 11:37 AM
#23
Re: Why am I too slow?
Ok, carb is killing RPM's. As long as his engine is set up similar to a ZZ502 might as well bolt on a Holley 850 (good to 5800 RPM's) Nickerson's set my 850 up (vac secondaries) jetted 82 primary & 88 secondary with 4.5 power valve, and works pefectly so seems this would be a good starting point. Whatever carb you get, be sure it's a MARINE carb.
Still have that +,-19% prop slip to contend with. I have the same deep prop and hook similar to Mike Paula, and slip is around 13% so that hurts some.
Bottom paint being there in patches must be creating allot of drag? Seems like that chit has gotta get gone.
Oh, what kind of oil cooler do you have, and do you have a sender/gauge for oil temp? If not I'd highly recommend it !!
Still have that +,-19% prop slip to contend with. I have the same deep prop and hook similar to Mike Paula, and slip is around 13% so that hurts some.
Bottom paint being there in patches must be creating allot of drag? Seems like that chit has gotta get gone.
Oh, what kind of oil cooler do you have, and do you have a sender/gauge for oil temp? If not I'd highly recommend it !!
Last edited by Kidnova; 10-01-2006 at 11:50 AM.
10-01-2006, 09:58 PM
#24
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Re: Why am I too slow?
Originally Posted by Kidnova
I've been running a ZZ502/502 in my 23 Wellcraft Nova for 4 seasons and no signs of reversion. 1 season with stock Merc exhaust...no signs of reversion. 3 seasons with Revolution Marine exhaust and no signs of reversion. Running a labbed 25P Mirage generally turning 5050 to 5100 RPM's. Will do +,- 68-70 MPH any day all day. Best WOT so far is little over 73 gps.
The Nova has a slight hook probably about +,- 18-20 inches up from the transom. 4 foot straight edge shows the hook is about 1/8 inch deep. Haven't checked/measured for a while but think thise numbers are pretty close. Prop shaft center is about 7 3/4 in. below the bottom of the boat...way deep by totays standards.
23 Nova's are not known for a fast/efficient hull. I would think your 251 would be several MPH faster at WOT than a similarly powered 23 Nova. I'm sure the bottom paint is holding you back some, like Griff said.
Sounds like you have the ZZ heads along with the ZZ cam. What are you running for a carb, and how is it jetted? Your turning a 23P at 5000 to 5100 RPM's. A ZZ turns a 23 at over 5600 R's. When I tried a 23 I pulled back on the throttle at 5600 while it was still climbing. If your going 60 MPH turning a 23P at 5050 RPM, your prop slip is around 19%. That's very high. Could be the bottom paint plus not trimmed properly ?
The Nova has a slight hook probably about +,- 18-20 inches up from the transom. 4 foot straight edge shows the hook is about 1/8 inch deep. Haven't checked/measured for a while but think thise numbers are pretty close. Prop shaft center is about 7 3/4 in. below the bottom of the boat...way deep by totays standards.
23 Nova's are not known for a fast/efficient hull. I would think your 251 would be several MPH faster at WOT than a similarly powered 23 Nova. I'm sure the bottom paint is holding you back some, like Griff said.
Sounds like you have the ZZ heads along with the ZZ cam. What are you running for a carb, and how is it jetted? Your turning a 23P at 5000 to 5100 RPM's. A ZZ turns a 23 at over 5600 R's. When I tried a 23 I pulled back on the throttle at 5600 while it was still climbing. If your going 60 MPH turning a 23P at 5050 RPM, your prop slip is around 19%. That's very high. Could be the bottom paint plus not trimmed properly ?
10-01-2006, 10:22 PM
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Re: Why am I too slow?
Edited that last post...Flowed 800. not a 600. It flowing well over 850cfm. Like I said its jetted the same as the stock 502/502 850. Plugs have perfect color.
Heads are the I/E- 2.19/1.88 valves 290/110CC.
Oil cooler and new 8 qt pan was in before the motor was ever started. Temp is 180- 210 PSI has never droped below 50psi
oil temp gauge was added when i redid the helm and installed new SScomp gauges
Heads are the I/E- 2.19/1.88 valves 290/110CC.
Oil cooler and new 8 qt pan was in before the motor was ever started. Temp is 180- 210 PSI has never droped below 50psi
oil temp gauge was added when i redid the helm and installed new SScomp gauges
Last edited by Mike Paula; 10-01-2006 at 10:29 PM.
10-02-2006, 04:31 AM
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Re: Why am I too slow?
I did the bottom paint on my Donzi 25 and it made i recon 6 MPH or more. I did exaust and went from Mirage plus to Bravo 1 as well and made 11 MPH. Could not have predicted that much. Do the bottom paint and try a 4 blade prop. The extra lift will stop some of that water spill as well. I would be very care full to goose the gas pretty goog befor shutting down the engine with a 112 degree cam as well. Make sure you blow the last of thet water out. Jas
10-02-2006, 07:13 AM
#27
Re: Why am I too slow?
Originally Posted by k24u
Kid I have the same boat as yours built the 454 I just got clocked today on radar at 62 mph turning a 23 mirage turning 5500rpms I have a bravo 1 labbed 24 I did not have that on It will turn 5150 with that prop. A while back at a poker run had a guy tell I was running 73 on his gps with the 24 does that sound right or am i way off
73 MPH at 5150 with a 24 inch prop would put your slip at around 6.5. That's pretty "optimistic" but maybe possible ? I can't say, as I'm no prop/slip/hull expert.
Best thing to do is pick up a cheapy hand held gps and spend some time prop testing. Regardless, if you're poker run bud is right, congtrats, as you must have a very strong running 454.
btw....in calculating the the prop slip I'm assuming you have a Bravo with 1.5 gears...that right ?
10-02-2006, 08:13 AM
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Re: Why am I too slow?
Originally Posted by Kidnova
Did you mean "72 mph" with the 23 Mirage? That's possible as last time I looked at my gps, I was at 71+ with my 23. It was very choppy that day so I was concentrating on driving, as well as looking at gauges & speed. 62 mph with a 23 would put your slip at a little over 22%, which is very high.
73 MPH at 5150 with a 24 inch prop would put your slip at around 6.5. That's pretty "optimistic" but maybe possible ? I can't say, as I'm no prop/slip/hull expert.
Best thing to do is pick up a cheapy hand held gps and spend some time prop testing. Regardless, if you're poker run bud is right, congtrats, as you must have a very strong running 454.
btw....in calculating the the prop slip I'm assuming you have a Bravo with 1.5 gears...that right ?
73 MPH at 5150 with a 24 inch prop would put your slip at around 6.5. That's pretty "optimistic" but maybe possible ? I can't say, as I'm no prop/slip/hull expert.
Best thing to do is pick up a cheapy hand held gps and spend some time prop testing. Regardless, if you're poker run bud is right, congtrats, as you must have a very strong running 454.
btw....in calculating the the prop slip I'm assuming you have a Bravo with 1.5 gears...that right ?
10-02-2006, 10:30 AM
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Re: Why am I too slow?
Ok At work and have my notes on the carb. The Carb is a 4780 / 4150 I have Jetting is P @78 and S@ 82 And a 4.5 Primary power valve and a 6.5 in the Secondaries.
