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Need a rebuild

kevnmcd

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I have a buddy in Havasu that needs a rebuild on a 502 mpi in a conquest deck and would like to add some hp to it +\- 100 hp with some minor mods. Everyone in Havasu is telling him to convert to carburetor because they don't know fuel injection mods. Who would you use and why and do you have experience with them?
 

McRib

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I have a buddy in Havasu that needs a rebuild on a 502 mpi in a conquest deck and would like to add some hp to it +\- 100 hp with some minor mods. Everyone in Havasu is telling him to convert to carburetor because they don't know fuel injection mods. Who would you use and why and do you have experience with them?
Everyone? Who is he calling? Jose and hose b's motoworld? Lol
 

kevnmcd

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Everyone? Who is he calling? Jose and hose b's motoworld? Lol
"Everyone" he has spoke to so far. I have to think there are some EFI guys in Havasu that are good.
 

McRib

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"Everyone" he has spoke to so far. I have to think there are some EFI guys in Havasu that are good.
Barrett would be a good start. I can't imagine him saying no. Absolute works on all the big boys stuff.
 

rush1

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I have a buddy in Havasu that needs a rebuild on a 502 mpi in a conquest deck and would like to add some hp to it +\- 100 hp with some minor mods. Everyone in Havasu is telling him to convert to carburetor because they don't know fuel injection mods. Who would you use and why and do you have experience with them?
Boats total junk I'll haul it away for him for free! :D
 

Bobby V

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I talked with Flattop Marine about a rebuild on my 502. He didn't say anything about changing the EFI.
 

Bigbore500r

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Don't ditch the EFI. Your problem is going to be the stock intake manifold and throttle body. 100hp is easy with aluminum heads and a small cam. That intake manifold on the Merc 502 mag is a GM truck piece and doesn't flow well. Some people shorten the runners inside and port it but it still is restrictive. That's why Merc 500 EFI and 525 EFIs come with a shorter runner intake with larger throttle body, to support that 100+ extra HP of air and allow it to breath to 5500 rpm. I wonder if you can get a take-off 525 intake setup complete with throttle body, injectors and fuel rails. You might have to change a few harness plugs but that would seem to be the ticket to me. Maybe a shop has a setup that was removed when a customer when Whipple?
 

Ibeplumbing

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Just have him take it to Larry Peto in Tucson or B & D. Proven builders, you know what quality you are getting
 

Melloyellovector

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Barry, obnoxious1 here on the boards, in Parker. He built mine
100hp should be pretty easy.
I may even have take off parts from mine that would get him his 100hp, Barry would know best on that or not
990 heads, manifold, Imco power flows, Iv got boxes of shit I'll list eventually unless Barry needs for something he knows what Iv got for the most part
 

obnoxious001

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You can't go too far with cam on the stock 502EFI setup. I did one earlier this year with just a cam change, and mild at that, but user claims his boat picked up 5mph pulling a skier in the Catalina Ski Race.

If he wants more power, it becomes a matter of injectors and controller, and more than just a few bucks. Actually got into some pricing on the injection with Brian at B&D, who rebuilt the drive an installed the engine after I put it together.

I don't know that Barrett builds any engines, they are installing the one I did for mellowyellowvector.
 

Tackleberry

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You can't go too far with cam on the stock 502EFI setup. I did one earlier this year with just a cam change, and mild at that, but user claims his boat picked up 5mph pulling a skier in the Catalina Ski Race.

If he wants more power, it becomes a matter of injectors and controller, and more than just a few bucks. Actually got into some pricing on the injection with Brian at B&D, who rebuilt the drive an installed the engine after I put it together.

I don't know that Barrett builds any engines, they are installing the one I did for mellowyellowvector.
Any thoughts on ASM's short runner intake, they're claiming 525 HP @ 5400 with just a cam change.
 

obnoxious001

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Any thoughts on ASM's short runner intake, they're claiming 525 HP @ 5400 with just a cam change.
I have not researched the EFI stuff, just some conversations with Brian at B&D since we've known each other a long time. ASM is pretty highly respected, so I would think their statement would be true. It would be interesting to see how much of the gain is due to cam vs intake. It's very typical for GM to understate advertised power, not sure if Merc plays along with that or does their own testing and horsepower statements.

Personally, I figure any mild performance engine I put together should make over 1hp per cubic inch, but do not get to dyno everything I assemble. Any engine that I have sent to the dyno exceeds that number.
 

kevnmcd

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Andy B.

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Very interested in this since my 99 502 has over 600 hrs and getting a little tired even after being locked up three years ago(still gets to 4700 rpm same prop since I bought it use to hit 4900 or so) my buddy saved me a complete rebuild another shop told me I needed! I don't need anything crazy would like at least 500hp and I would need the motor removed also I don't have the means.
 

rivermobster

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Barry, obnoxious1 here on the boards, in Parker. He built mine
100hp should be pretty easy.
I may even have take off parts from mine that would get him his 100hp, Barry would know best on that or not
990 heads, manifold, Imco power flows, Iv got boxes of shit I'll list eventually unless Barry needs for something he knows what Iv got for the most part
Yep. Have B&D Custom Marine pull it out and send it off to Barry.
 

AzGeo

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There is horsepower and then there is torque .

I've had friends who wanted 'a little bit more', and I tried to keep their projects 'as stock as possible' .

On a 454 Mag MPI I did the motor to a 496" and added a larger fuel pump, with a matching adjustable pressure regulator . On the 502's , I went to 540", with the larger pump and regulator .

Using the stock (unfuckedwith) ECM, I manipulated the fuel pressures for the larger cubic inches, and used a 'variable rheostat resistance' to control the 'cold VS hot fuel curves' .

The stock ECM wants to see 160 (F) or more hot running temps, I used a 140 (F) thermostat to keep the 'detonation' down and adjusted the variable control to get the ECM to the place it liked to be .

Using the stock ECM is great for drive ability, but it does have a 5080 RPM limiter on it . Any RPMs under 5252 are TORQUE and above RPMs are horsepower .

This is exactly why I chose to make more torque and not more horsepower .

I've always used the Crane cam that is used in the 500/525 HP Mercruiser motors for these stock ECM builds . Both flat tappet and roller, with great success .

The last one I did was a 25' Daytona tunnel . 454 Mag, into a 496" with the larger cam, fuel pump and regulator . It went from a 23 pitch 3 blade to a 28 pitch 4 blade that hits the rev limiter on most waters . No other external additions, stock all around .

Take it to Barry, have him build the motor, and add on the simple items I have used to make it more powerful without the expense and problems of 'reprogramming the ECM' .

Good luck and have fun ......
 

obnoxious001

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Yep. Have B&D Custom Marine pull it out and send it off to Barry.
I would be happy to work with him, but the engines that I built and Brian installed were both deals that I sent to him I think.
 

Duck'ed_Up

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Barry, obnoxious1 here on the boards, in Parker. He built mine
100hp should be pretty easy.
I may even have take off parts from mine that would get him his 100hp, Barry would know best on that or not
990 heads, manifold, Imco power flows, Iv got boxes of shit I'll list eventually unless Barry needs for something he knows what Iv got for the most part
Not to thread jack but are you looking to get rid of those imco power flows?
 

Melloyellovector

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Not to thread jack but are you looking to get rid of those imco power flows?
Fully polished and cleared manifolds, and freshly polished risers. I purchased from a member on PB, but BCM convinced me to run new CMI's. So yes they are avail. How much you offering? I believe I paid 800, before polish and clear. I know I'm not getting my money back but ??? How much you thinking. They will need new gasket kit, was all removed for polishing. I had but AJ " borrowed " the kit, lol
I'll have a shit ton of parts to list once mines complete, from take off stuff, and other stuff ordered that we decided to change or have 1 off parts made for instead.

Pm me if interested, I can send pics
 
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