DallasHeat

I have a 1998 28 Heat, stock 502 EFI. I'm considering adding CMI polished headers. Has anyone added these to a 28 - 502? Doesn't look to be a lot of room. What will I need to replace?

Anyone

DallasHeat

Indy

Actally there should be a ton of room. It's probably a good idea since the manifold/riser area has been a problem for the 502s for years. One of the things Merc did was to eliminate that whole assembly and install stainless/aluminum in the new 496 instead of the cast iron that's on the 502. If anything, you might have to modify or change the tailpipe for the conversion. You might want to call someplace such as BAM Marine (www.go-fast.com) and see how much different the CMIs are as far as where they terminate compared to the stock setup. I'll bet they are very close and you won't have to modify much.

39 Unlimited

Hey Dallas Heat,

I owned a 1995 Heat with a 540 Bulldog boat ran 71, installed a 420 mega blower 4lbs of boast boat ran 85 solid as a rock.

The blower would go nicely with your new CMI's

Nordic Rules!!!!

DallasHeat

Nordic Gary,

Your absolutely right, a blower would look great on this engine! The problem/concern I have is that I need something "turnKey".
I'm pretty good mechanically, but I don't have any experience with Blower motors. If I get to the lake and the boat won't start "Stand Back", I get pretty wound up!!! I would consider a 500 EFI.

Dallas Heat

DallasHeat

I've heard that just by adding the headers you could see 30-70hp increase? Is this just the salespeople talking? What sort of HP gain do you think I could expect?

Dallas Heat

39 Unlimited

I have the 500 efi's with standard CMI's - spoke with the merc tech at the Miami show he said just the upgrade from standard CMI"S to the sweeper long tubes was 30 hp. I say count on 50.

Nordicflame

Hey DallasHeat,
the CMI's fit just fine and look nice too!!!
They're a bit costly due to the "S" pipe configuration tail pipe. I think $3200 complete (full polish elbow tops) from Performance Marine (Rod Dash) in Oshkosh was the best price I could find.
Let me know if you have any questions. They're fresh in my mind beings I just pulled them off in preparation for a supercharger project.
Later,
Dave

DallasHeat

NordicHeat,

Can I use the s-pipes from my stock exhaust?

DH

rv

Assuming you have the Merc stock exhaust and the one piece aluminum S pipe, no you can not use that with the CMI's. The CMI's has a special connection between the end of the collector and the start of the tailpipe. Take a close look at a picture of them and you will see a special band clamp. Your stock S pipe requires a 4" hose to connect to it and there is no long flange area on the collector end to get a good hose seal.

Sorry, you need to spend the $grand.

Rick

Nordicflame

Hey DH,
like Rick mentioned they wouldn't work. You could use the transom elbow at the bottom, but that would be about it. The CMI tail pipe for the S pipe configuration goes back about 6" then drops straight down about 10". These are water jacketed and don't dump the water in until the end of that drop. This is a good thing for water reversion issues which you will need to concern yourself with when you you start adding power. (It's only a matter of time )
Later,
Dave