Randy my guess is that intake is holding you back around 30-50hp,over a nice carb and intake set up,on my dyno i have run a stock 502mpi only made 400hp,with the same basic engine with a holley850 and dual plane intake we make around 450hp,that intake makes great torque at very low rpm 1800-2500 would probably work good in a truck or ski boat,if you have it worked with shorter runners and some porting will help,Hey pat i have a complete 502 mpi set up i just pulled off a merc engine,iI have everything you need to go to mpi 650 and its yours,I plan on turning this 502 into a 575-600hp and i am going to use a merlin intake and holley hp950

That's about what we were thinking Dave. I'm halfway leaning towards a single plane efi set up with a 1000 cfm throttle body. Something like the Victor Jr efi set up. It is about the same price as a carb and manifold if we go new. I already need to have my tailpipes modified or get new ones due to the new heads having slightly higher ports, so I can add O2 sensors for tuning the efi without pulling and placing on the dyno. If we do that, then I won't have to change ignition. I imagine that should give the same power as a carb setup being that the manifold would be about the same. You don't have any used setups like that do you Dave?

Thanks Brian!

Hi Dave,
I don't want to derail Randy's thread, but I know he likes to talk engines so what the heck.
I have a gen VI 454 short block, heads from a HP500, cam from a 500EFI, AZ Speed intake off a Volvo Penta 7.4GSI, and a few other goodies in my stock pile.
My plan is to build a 450+HP 454 EFI.
So what do think about the AZ Speed intake vs. the Merc?
It must be a little better since Merc Racing uses it on the 525EFI right?
Anyway, I'd like to get my hands on a MEFI-3 ECM and wiring harness rather than using the MEFI-1 I have. Randy's ECM might work without much of a program change; I know his cam is very similar to the 500EFI cam. I'm not really looking for a complete system but extra parts are always nice...

The arizona-merc500-525 intake set up much nicer than the old merc 454-525mpi set up,I reworked a couple of merc 500efi,bigger cam,afr 315 cnc ported heads,55lb injectors,arizona monoblade,aeromotive fuel system we made 600hp at 5100,680 ft torque at 4000 or so,intake makes great torque but does't like to rev past 5200-5300,engines went into 42 cig so worked out great,if they were going into smaller lighter boat a single plane throttle body style efi probably would work a little better.I am having a merlin x intake modified for fuel injectors,going to use 65lb injectors,2000cfm throttle body,mefi 3 ecm,should work out nice,I bought the mefi burn system this winter works nice,the mefi controller is one of the most reliable ecms out there and prefer them to the aftermarket stuff.I don't have any single plane efi set ups for sale but i might have an extra mefi3 and harness around.All the efi stuff is cool(expensive too) but a good merlin x intake with a worked holley carb will run great,make just as much power or more than efi and be easier and cheaper to maintain

Thanks for the info Dave.
You know the boat I've got and I do need good low end torque to get her moving. The EFI stuff is expensive and I have been a little frustrated with it this year. I'm going to see how it goes when I put this new engine together. If the $$ start gettting out of hand with the EFI, I've got an intake and carb sitting on the shelf too.

We had some good water yesterday. I got her to run just a tick under 77 with our labbed 25P Mirage plus. that speed was with me, the wife, and over 1/2 tank of fuel. I was kicking myself for taking the hydromotive off. I think we would have see over 78 easy. It is going back on next weekend for a little more testing. I'm betting that with they Hydro, low fuel, and just me, that I can get awfully close to 80.

A custom labbed 28p Bravo 1 will be the fastest prop for your boat. Believe me when I tell ya...:drink:

When I talked to Brett about that, he didn't think I could turn it. On the stock 27P M+, I couldn't break 4800 rpm. The 26 Hydromotive I got to almost 5100 rpm. With some lab work on it, I know it would go. I've been eyeballing some 26 B1s on ebay. I know you've said before that the B1s are light on pitch, but light by 2"?

Yes, it does sound like a 28p B1 would be a little too big if you want to be at 52-5300, but you won't know until you try. Try both the 26 and 28 on the same day same conditions to see which the boat likes better. Call BBlades, they have test props.
With my old boat the the 502 would spin about 4700 with a stock 28p B1 and 4800 with a stock 27p M+. I had both props dialed in by Brett to reach 49-5000rpm running light which is where I wanted to be. For some reason my boat always liked the bigger props. Even when I had just the 310HP/7.4MPI in it, it ran better with a 26p vs. a 24p. People would tell me to have the thing run at the high end of the RPM range for top speed but it did not work out that way. As long as your not lugging the engine, your good.
A prop can be labbed to gain as much as 300rpm. Speeking with Brett, he said he can do more with a Merc Bravo 1 than the Hydro QIV-X.
Have fun with it! and be safe...:drink:
I sure wish I was to the point of dialing props...:rolleyes:

I have to say I agree with Pat, my old boat with a 496 (375) pulled a labbed 28 @ 4800. I added some cup to the tips for more bow lift. The boat would run some real good speeds with a light load and one person, unfortunately not enough HP to break 75 with fuel and a couple of people.

Hey Tim....You still up an around the islands? I am planning on heading up there this weekend starting on wednesday. If you are around let me know.

Jay I will third with T-Islands and Pat have mentioned. I am currently spinning a 26 Bravo but that is only because my max rpms are around 5500-5700.

Talk to this fellow, he bought my old props. Maybe he'll let you try one.
http://www.offshoreonly.com/forums/s...=131995&page=5

Elliot, I will be there Thursday night for 10 days. Hopefully get the boat in the water Friday need to change oil etc. We are having a party on Saturday on the island. Beer food and boats....you should come by. I am on Grindstone Isl on Swiftwater point which in in the Picton channel. Send me a PM....

Sorry for the thread hijack

No problem T!

I changed the plugs and oil this weekend for the poker run. Ran my 25+ with 5 guys on the boat, 40+ gallons of fuel, 2 full coolers, + all the other crap that goes along. We were in the Grand Poker run. With all of that, I still hit 72 mph, and it did it all day (except when it rained most of the day). It almost seems like it is getting a little faster with time. It has about 30 hours on it now. the water was just about perfect for the most part as well. One of these days, I'm going to do a low fuel solo run just to see where it goes.

Me by myself

26P Hydromotive Quad IV-X

1/4 Tank of Fuel

At LOTO Thursday afternoon

83MPH GPS - GPS pic to follow

I'm just a little stoked!

What rpms?

Last I looked was 5300 rpm and climbing. I think I might have hit the limiter as it seemed to sputter a little. That is when I shut it down.

All supers being narrow are very weight sensative. 83 is a good number. Congrats

Vary nice number!
I bet you don't want to sell her now.

I about crapped myself when I pushed the recall button. I was trying to think of ways to discredit it. We towed the boat here, and I thought maybe it was a number from being on the trailer, but there was no power to it then, and I checked the recall before I made the run and it was at about 75. I'm going to have to see if I can do it again on Sunday when I drive her back to the ramp.

Well, your rpms are good now.
Looks like a 26 is where you want to be.
Maybe a labbed 28, or a 27, but i don't really see why.
83 is very fast in a 24. Congrats!

Yeah, now I have to buy one of these props. I don't think the Hydromotives are cheap either. Oh well, it's only money I suppose!

Since I hadn't seen the speed I wanted, I was planning on building a bigger powerplant. After yesterday, the wife said "do you really need to build a bigger engine now?" My answer: Of course!!

In all reality, I'll probably leave it alone now. I made better speed than I had hoped for, and it is reliable as all get out. I really don't think I could ask for more.

Thanks for the congrats!

The Hydros are true on pitch and the prop you ran sounds like a great one.
A 28p B1 can be anywhere from 26.5 to 27p. The B1 and QIV-X are vary similar.
IMHO there is no need to go any faster than 80 in a 24' Super.
Be safe and have fun...:ernaehrung004:

Agreed:ernaehrung004:

Finally had a chance to take a pic of the speedo. Been working too much this week. I'm not even at the lake yet today! We're trying to get moving though.

All in all, it may never make that number again, but it did it once. That's all I need for now.