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Doing a Donzi differently - out with the 502MPIs in with the LSA blown 6.0s

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Doing a Donzi differently - out with the 502MPIs in with the LSA blown 6.0s

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Old 12-13-2017, 11:01 AM
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Originally Posted by 1989mach1
Taking the extra wight out will help but most not all but most non step boats benift from spinning out. My boat at 3500 to 4000rpms runs 50 55 on average have seen up close to 60 with some close together chop and the best I have seen was 83 at 5300 5400rpms. My brother with the 496s is about 50 cruse on the high end and tops out at 75 I believe he has seen. Edit drives on both boats 1.50 brovo1s. Mine will be running imco -0 lowers this coming season so will be getting a new set of numbers. We will see what happens there lol

Interesting. That seems like pretty good cruising speeds for you in a boat that seems like its propped to run up top yes? My goal was to be able to cruise at 65 at 4000 more so then run 90mph or something. Yours has @125hp on your buddies and @40 ft lbs of torque from the dyno info I could find, prob why only slight increase in midrange speed but sizeable top end gain? I should be around 120ft lbs more per engine and 200 hp, 850#s lighter, and the motors will turn 6500 easily if I need them too - I think that would be enough to hit my mid 60s target. Maybe get near 90mph if I was trying but who cares
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Old 12-13-2017, 11:07 AM
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Originally Posted by F-2 Speedy
are these take out 502's good running ?? if so are you selling them
[email protected] shoot me an email. Yes they are in good running condition, took it out to make sure all pressures good, no alarms, ran clean before I pulled it apart, was fighting some fuel issues at first but threw the fuel sysem Im going to run on that motor and ran good after. Hit me with an email and I can get you more info, I planned on cleaning them up and refreshing them before I parted ways, the previous mechanic who had worked on some dumb stuff stripped a couple holes on the upper intake manifold, cracked a temp sender stupid stuff like that was going to fix all that up because I wouldnt want anyone saying look at that sloppy **** like it came from me like that! He sure did me no favors but Ive seen more than a couple guys with 1000-1200 hrs on these engines and running good which is pretty damn impressive when I here about 525 guys dropping valves at 250 hrs like its their job LOL
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Old 12-13-2017, 11:42 AM
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The cruse speeds and top end speeds are higher with the twin step bottoms where they get more air under the boat and ride much much lighter on the water. They also have a very large plate that starts at the first step getting bigger at the second step. I figured out my wight some time back when I was getting my lift and with full tank of gas water and gear I was just under 12k lbs they are heavy wide boats but run good for there size. Only thing I don' have is a generator and vacation flush system.
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Old 12-19-2017, 10:14 AM
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Pretty much have the oil system figured out. Pans have -10 bungs and no filter housing provisions, running from there up to remote oil filter housing with a thermostatic bypass to the oil cooler, so it will get up to temp to burn off any water/fuel contamination. Using oil filter that can hold almost 2 quarts extra to park a good bit in the system. Reusing the existing Merc oil/pwr steering coolers as that saves changing up a plumbing run from pickup to pump to cooler really at all. Figured out the oil passage fittings in the OEM cooler are 1/2" inverted flare thanks to Russ at Mr Cool I believe is the company but could only find 8 AN adapters to that, so the oil cooler circuit will be in 8 AN. Which probably isnt a big deal as oil wont flow through that side until it gets hot and then the viscosity is way down anyway.

Should make changing oil easy, also likely will be putting a drain valve fitting on the end of a hose screwed into the drain plug about a few feet long and attaching it vertically to something on the motor. That way i can stick a hose on the end drop it down bilge and out the bilge plug if I have it out the water and time to let it gravity drain, or just open the valve and pull with one of the vacuum pump whiles its attached to the motor if its in the water
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Old 12-23-2017, 11:56 AM
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Very cool build. Excited to see how it turns out for you!
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Old 12-24-2017, 12:14 PM
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Originally Posted by 1989mach1
The cruse speeds and top end speeds are higher with the twin step bottoms where they get more air under the boat and ride much much lighter on the water. They also have a very large plate that starts at the first step getting bigger at the second step. I figured out my wight some time back when I was getting my lift and with full tank of gas water and gear I was just under 12k lbs they are heavy wide boats but run good for there size. Only thing I don' have is a generator and vacation flush system.
Have you seen step and non step ones with identical power, to see what the difference is cruising at 3500 or so and full tilt?
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Old 12-24-2017, 01:27 PM
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No I have not ran side by side with a non step 33.
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Old 12-24-2017, 02:51 PM
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Originally Posted by 1989mach1
No I have not ran side by side with a non step 33.
Ive actually seen some test data that showed a step hull to be faster at max speed, but 3 or 4000 rpm cruise was actually a little slower/more fuel consumption. I think it was a Active Thunder, or something I saw them do test on (Wasnt a Cig, Fountain, Donzi) Prob completely dependant on hull design but I could see on some where it would be slightly worse up to the point where you were going fast enough to take effect
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Old 12-24-2017, 04:00 PM
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I could be wrong but I can' think of any non step boat being more efficient then a step boat. Two different boats but my bud had a 35 cig mistress about the same wight as the 33zx just over 12k I believe and was running mid 70s with 700hp per side. Like I sead not the same boat but a way to see how much power it takes to get a non step boat to run above 70
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Old 12-24-2017, 04:16 PM
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Originally Posted by 1989mach1
I could be wrong but I can' think of any non step boat being more efficient then a step boat. Two different boats but my bud had a 35 cig mistress about the same wight as the 33zx just over 12k I believe and was running mid 70s with 700hp per side. Like I sead not the same boat but a way to see how much power it takes to get a non step boat to run above 70
it does take a bit of power to get a ZX moving anyway but a step bottom in any boat whether it be a Fountain, Donzi or Cigarette usually will be 4 to 5 mph faster. Plus the set up on a newer step boat is usually different, Drive height, lower cases, etc. It just takes too much hp to get a straight bottom boat moving in the direction we all want to go or can afford to go.
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