'96 252 454 Magnum performance benchmark

akorcovelos · Post by **akorcovelos** » Sun Sep 30, 2018 2:22 pm

Here's the run down:
1996 252
454 Magnum MPI
Bravo 3
1/2 tank of fuel
2 people in the boat, no other gear.
Ambiant air temp 58*
Empty lake, water dead calm.

Time to plane: 5 seconds
Slowest planning speed: 16mph @ 2200rpm
Cruise speed: 48mph @ 4000rpm
Top Speed: 57mph @ 4900rpm

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I was impressed overall with the performance of this boat, especially with 900 hours on the clock. Also pretty surprised at how accurate the dash speedo is compared to the GPS speedo. They were within 1-1.5mph through the entire test.

Looking for a good MEIU 1 to send to Whipple for their 91 octane tune, so we'll see how it compares to stock.

Unfortunately I'm probably winterizing next weekend so the comparison will be in the spring...

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skno · Post by **skno** » Fri Oct 05, 2018 7:33 am

That sounds like some pretty good numbers. what prop?

AsLan7 · Post by **AsLan7** » Fri Oct 05, 2018 7:53 am

Some great performance akorcovelos. I bet you'll hit 60 with a 1 to 2 foot chop.
Looking forward to your spring report!

thunder550 · Post by **thunder550** » Fri Oct 05, 2018 10:44 pm

Whipple does tuning for otherwise stock engines? I'll be curious to see results.

akorcovelos · Post by **akorcovelos** » Mon Oct 08, 2018 9:39 am

Thanks all.
Props are stock 28p B3 that badly need balancing, which will happen over winter.

I'm contacting Arizona Speed and Marine to discuss their reflash as well. Thunder550, yes, there are a coupl etuners out there that optimize the factory MEFI-1 & 2 tunes for premium only, claiming 25hp and cleaner idle. We shall see. I'm probably going with Whipple because they are a stronger name in the marine performance industry, but a member on the Cobalt owners group on FB used the AS&M tune on his 502 and likes it, so worth calling and talking to them.

Big Block Power · Post by **Big Block Power** » Mon Oct 08, 2018 12:44 pm

Arizona speed has been around for along time. Don't rule them out. I would buy 2 extra ecu's 1 from each of them. Lol

thunder550 · Post by **thunder550** » Mon Oct 08, 2018 10:38 pm

I've been to ASM awhile back, good guys. I wonder what the extra power tune does for reliability.

akorcovelos · Post by **akorcovelos** » Mon Oct 08, 2018 11:28 pm

If it's a good tune, reliability shouldn't be an issue. This is early EFI tech, and I guarantee Mercruiser went way safe on the tune back then. The premium fuel tunes just advance the spark curve and lean out the fuel trim tables, and probably adjust injection PWM to be a bit more aggressive. It bumps redline to 5400rpm as well, so I can have the props labbed which would put it into the mid 60s if estimates are correct.

Once I sell the car tuning gear I have I'm buying another MEFI 1/2 to send out, to who I'm not sure. I'm going to call AS&M and Whipple and see who I like more. The guy I was chatting with likes his AS&M tune, and all he's done is MSD ignition and a K&N spark arrestor.

I've email back and forth with someone from Whipple a couple times and he hasn't been super helpful, but a phone call may give me a better feeling about them.

thunder550 · Post by **thunder550** » Tue Oct 09, 2018 8:44 am

I've seen 59-60 mph at 5150 RPM, an extra 300-350 RPM would put me at 62 with the current prop and same slip numbers. Going to a 22 pitch prop would get 65, and if it added enough power to turn a 23 it would get up to 67mph. Interesting...I'll have to keep an eye on your guys progress. On a normal day out at the lake I'll burn probably 10-15 gallons, so the cost to switch to premium for a daily trip would be relatively small. A full 73 gallon tank would be quite a bit more, but that's rare.

ASM is local to me, so if I were to do it I'd go with them. Damn it, you guys are going to make me spend more money again. WTF.

akorcovelos · Post by **akorcovelos** » Tue Oct 09, 2018 10:41 am

You can hit 5150RPM on stock tune? Maybe because you have a Bravo 1? Nothing I did would put me past 4900rpm on my testing. If I had another 200-300RPM that alone would put me into the 60s.

thunder550 · Post by **thunder550** » Tue Oct 09, 2018 11:06 am

That's what the tach shows. Could be that the tach is off a bit, not sure. My original Mirage 23 would top out right around 5000. I tried a Revolution 4 23 and could only hit 4600, switched to a Rev4 21 and showed 5150. I've never hooked a scanner to it to validate the tach is reading correctly.

akorcovelos · Post by **akorcovelos** » Tue Oct 09, 2018 1:13 pm

The ability to tune props on the Bravo 1 is nice. I'm pretty locked from that perspective with the B3...BBlades and a local performance prop shop can massage the props I have now, but I've been told the B3 will become a limitation on top speed once I break the 60+mph mark. The upper is the same for B1 and B3, so if I ever feel like it I could swap legs and play with propping, but I love the low end and mid-range torque of the B3. The boat jumps from 20-50 so hard it puts you back in the seat.

thunder550 · Post by **thunder550** » Tue Oct 09, 2018 10:51 pm

Given the choice I think I'd rather have the B3.

akorcovelos · Post by **akorcovelos** » Wed Oct 10, 2018 9:06 am

Yeah, for what the boat is the B3 is perfect for our needs. Like I said before, it will never be a go-fast boat so I'm willing to give up a few MPH for the better performance low and mid-range.

akorcovelos · Post by **akorcovelos** » Thu Oct 11, 2018 10:41 pm

Sad day, winterized the old girl. She'll be getting shrink wrapped in the next week or two.

Gratuitous engine pic. The whole boat, including the engine and bilge is getting detailed in the spring.

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Saw these two plugs cut off and zip tied to the wire box. Anyone know what they're for?

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