502 performance from a 7.4?

[akorcovelos]

You knew this was coming right?

This boat checked every box except the power plant for me, but it was SO clean I couldn't pass it up. It at least has the 7.4 Magnum MPI 385HP, so it's not a turd. I'll pull some GPS numbers Saturday, but the dash speedo indicates mid 50's which seem realistic based on my research.

What I would like is to get the 7.4 up to 8.2 performance, so nothing crazy like Whipple charging (yet ).

Does anyone have any experience with this: https://whipplesuperchargers.com/index. ... uct_id=410

Are you wanting more out of your 454 or 502 Mag MPI engine? Whipple engineers have developed a custom calibration for all 454/502 MPI's that maximizes the engines power capacity by increasing the RPM limit, increasing spark advance and modifying the fuel curve to give your boat a cleaner transom and a better performing engine. By optimizing the spark curve for 91 or better fuel, Whipple was able to extract 25HP more while not sacrificing stock reliability. The recalibration also features a 5400rpm limit over the stock 5100rpm which gives you plenty of prop choices. Whipple offers many custom calibrations for built and highly modified engines.

This would put my 7.4 5hp shy of a stock 502, so theoretically it should put the boat into the low 60s, which is what I'd like. Having to run premium kinda sucks, but I can only get mid-grade and premium on the water here anyway so it's not that much more expensive fuel wise.

I'm also taking my B3 props in to be cleaned up, balanced, and mirror polished. I'd be surprised if that net me 1mph up top, but it will hopefully eliminate the B3 vibration at low RPMs. I'll index the props when I reinstall also, though I know it's a debated topic. Worth the time even if it helps nominally.

So what say you?

[Big Block Power]

T5555555000000 what are you running? Mid 50's?
First the b3's are stealing mph from you. Call and talk to bblades ask them what they think. Whipple is a very good company.

[akorcovelos]

I'd be open to swapping a B1 lower on if need be. I like the low and mid-range performance of the B3, and I've read they are well capable of mid-60s which is all I'm really looking for at this point. If I went to a B1 I have several props to play with since Alpha props fit them, 3, 4, and 5 blade.

I also plan to put tabs on, though not sure if I'm going Smart Tabs or hydro tabs yet.

[cmattj]

Fun but are you doing a in Boat bolt on? Or is it’s coming out? Heads off??

My suggestion if you want to keep the bones stock, but pick up some hp is in 3 areas.

Exhaust.. EMI thunder headers ( 454 bravo heights)

Camshaft lifters. Valve springs ....Extreme marine 270. Non- roller ( keep it on a 112-114 lobe center for no water reversion)

Oil pan..... (upgrade to 502 style or marine with 8qts sump and front marine dipstick for ease of service and checking) you’ll have temp issues with oil if you don’t.

So this will give you 410 hp as long as the engine leak down is low and it still has decent heads.

Lastly for another 25 hp , have the heads milled 15thou ( you’ll still get the intake to bolt down and seal, but you’ll pick up compression to 9.5)

About a 4 k investment . Now we buy props.1k

Plan b.

Let’s find a take out 502 marine with a original roller cam set up , original 8 qt pan, and make 415hp. Do the same exhaust and cam upgrades and make 450hp For 8k

[akorcovelos]

Not wanting to crack the engine open until it needs it.

All that work you mentioned equals to the same net gain as the Whipple tune and premium fuel, am I missing something? I've tuned boosted cars and diesel trucks, there is always more left in a stock engine. Back in '96 I'm sure Merc went with a very safe tune fir their first gen fuel injection.

I'm keeping an eye on craigslist and such for a solid marine 502 to build in my shop over time, but for under $1k Whipple is claiming to get me within 5hp of the stock 415hp 502, why drop $4k to get the same numbers? This is assuming the Whipple claims hold true. It's a trusted brand/tuner so I have no reason to doubt them, but I also have no evidence to prove it. I may be willing to be the test mule on that...

[cmattj]

I caught the whipple charge comment so obviously I thought your going to put a system on it.

Sure try the remap. A plug and play is always good. Plus your hands stay cleaner.

I was giving you engine mod performance ideas. Whipple takes the rev limiter up to 5400 rpm so most of The advertised power is a result of remapping and higher rpm.

Oh .. the other way gives it a nasty rumpty rump idle. Lol

[akorcovelos]

haha, yeah this is going to be a long term boat for us, so I'm taking baby steps on mods. I don't want to pull the engine and boost it after 10 hours of use when the 7.4 runs perfectly. The dealer actually put it on a dyno and it ran within 5% of factory numbers, and in our first couple outings I was hitting 5200RPM at an indicated 57MPH on the dash speedo. It's a strong engine, and yes, I know GPS will bring some reality to the MPH.

I'm hoping to find a 502 to start building on the stand, then swap in when it's done. I don't want any down time on this boat. I'm thinking Santa is going to get me the Whipple tune this year. I'll pay the extra to keep my ECU so I can swap back to stock easily if I don't like the tune.

Off topic question, but can you still run the silent choice pipes off dry headers, or would that cook the outdrive/silent choice flappers?

[cmattj]

Off topic question, but can you still run the silent choice pipes off dry headers, or would that cook the outdrive/silent choice flappers?

Cook is the right word. And dry stack exits require mods to find the exits even without using the y-pipe diverter. It’s tight back there. The also have a secondary flapper to prevent water reversion ( that’s the tapping sounds you’ll hear at idle when CC is off)

“CMI” makes a sport tube header that should clear your hatch. ( riser high)

I like the “EMI thunder” too and have used them ( aligned perfectly with the bravo cut outs. ( bravo exhaust has it’s own angle of exit and widths)

Very loud! Yeah!!! And a direct bolt in.!

[akorcovelos]

Man, those EMI headers a purdy. At $2100 for the silent choice risers it's a bit out of reach right now, I'd rather spend that money on a 502 to start building. Definitely putting them on the wish list though.

I have a standalone MS3X setup sitting on the shelf in my shop, but I'm not sure how well that ECU would hold up to marine use...I have to reach out to DIY and see what they thought about it. I really just want to enjoy the boat though, so dealing with building the harness and tuning isn't really appealing to me right now...I may just sell the MS3X and use that money on the Whipple ECU, let them do the work for me, lol.

[Big Block Power]

You want to go fast and with no ecu upgrades, no engine upgrades, a little money boy do I have the fix for you.

[AsLan7]

Not wanting to crack the engine open until it needs it.

All that work you mentioned equals to the same net gain as the Whipple tune and premium fuel, am I missing something? I've tuned boosted cars and diesel trucks, there is always more left in a stock engine. Back in '96 I'm sure Merc went with a very safe tune fir their first gen fuel injection.

I'm keeping an eye on craigslist and such for a solid marine 502 to build in my shop over time, but for under $1k Whipple is claiming to get me within 5hp of the stock 415hp 502, why drop $4k to get the same numbers? This is assuming the Whipple claims hold true. It's a trusted brand/tuner so I have no reason to doubt them, but I also have no evidence to prove it. I may be willing to be the test mule on that...

.
Read thru this thread ......

viewtopic.php?f=45&t=701&p=11962#p11962

Then rewatch this vid.....

https://m.youtube.com/watch?feature=you ... TzFPr-ojbU


Then, PM Whippled263.


.








.

[akorcovelos]

You want to go fast and with no ecu upgrades, no engine upgrades, a little money boy do I have the fix for you.

Not sure I understand? I am planning on upgrading the ECU with the Whipple tune an premium fuel. That should put me the same performance level of the factory 415hp 502 equipped 252s.

[akorcovelos]

Not wanting to crack the engine open until it needs it.

All that work you mentioned equals to the same net gain as the Whipple tune and premium fuel, am I missing something? I've tuned boosted cars and diesel trucks, there is always more left in a stock engine. Back in '96 I'm sure Merc went with a very safe tune fir their first gen fuel injection.

I'm keeping an eye on craigslist and such for a solid marine 502 to build in my shop over time, but for under $1k Whipple is claiming to get me within 5hp of the stock 415hp 502, why drop $4k to get the same numbers? This is assuming the Whipple claims hold true. It's a trusted brand/tuner so I have no reason to doubt them, but I also have no evidence to prove it. I may be willing to be the test mule on that...

.
Read thru this thread ......

viewtopic.php?f=45&t=701&p=11962#p11962

Then rewatch this vid.....

https://m.youtube.com/watch?feature=you ... TzFPr-ojbU


Then, PM Whippled263.


.








.

haha, yeah that's hard to argue with. My neighbor has a Whipple charged Formula 28', does 78mph. Since having my kids I haven't had time to put in competitive seasons with the race car, so as much as it hurts I'm looking to sell it, as it hurts more to watch it sit in storage and deteriorate. The money from liquidating my road racing gear will slowly trickle into this boat, so my 3-5 year plan is to end up with some form of big HP power plant. If I'm going to drop $10-20k into a full Whipple kit with good exhaust and supporting internals, it's not going to be on a 454. I'll find a 502, or 540, etc. to build in the shop over time.

For my instant gratification I want the 454 to be on par with 252s equipped with the 502, not a crazy goal by any means. The Whipple retuned ECU seems to be the best solution to that end. It will keep me content until the right engine comes along. I'm patient, and in being so can usually find good deals on what I want.

Let's hope this thread is still going 3-4 years from now with a success story of swapping in a blown 500+CI monster that will run on pump gas, lol.

[Big Block Power]

You want to go fast and with no ecu upgrades, no engine upgrades, a little money boy do I have the fix for you.

Not sure I understand? I am planning on upgrading the ECU with the Whipple tune an premium fuel. That should put me the same performance level of the factory 415hp 502 equipped 252s.

I'll help you understand. This is the best and cheapest and fastest option you have. The Alpha 3 drive
It even helped Bobrae maneuver around the docks this year

[cmattj]

Sweet Outdrive.. Rumor has it you just put in gear and shell go on-plane..lol