View Full Version : 2005 mercruiser upgrades

09-07-2012, 11:02 PM
I've got a 2005 22zx, sporting a measly 5.7 mag mpi! Looking for upgrade ideas. I got in touch with procharger, they won't offer a kit for motors after 2001. The whipple kit is around 8k. Would I be better off to junk the fuel injection and go carbureted? Should I do an all out motor swap to a BB? I couldn't find a camshaft or head upgrade either.

Any info would be deemed as helpful, as Im a little on the fence at the moment!!

Thanks in advance,

Dr. David Fleming
09-08-2012, 12:00 AM

I also have a 22ZX which I changed out the 454 for a 502. The basic simplest rule for go faster is "there is no substitue for cubic inches." A used 502 or 496 is the quickest fastest way to more power and is the reason the factory offered bigger engines. The average life of a standard Mercruiser marine engine is on the order of 400 hours. This goes for the 5.7, the 454 or the 502. When you use a procharger or highly up the power of an engine the service life can be as short as 100 hours. Your cheapest upgrade would be a 502 with factory carburator - next would be a larger 2005 engine like Donzi would have put in the boat. All of these changes cost and you need a financial war chest to do it.

09-08-2012, 11:33 AM
What drive do you have? I know some SB 22x's had Alphas, that can lead to many more $$$ to upgrade.


09-08-2012, 11:03 PM
Bravo one. It came with a 24 pitch bravo aluminum prop. I cant turn more than 4800 rpm with just me in the boat and half full of gas. I have a lab 23 that I want to try, maybe a few more rpm would make a difference?! I've also heard of flashing ecm's to make more power, but running rich or a stronger spark is minimal power upgrades! I don't mind a motor swap, I found this boat at a repo auction so I wouldn't be too upset at a upgrade that would cost <10,000. Longevity is my biggest concern!!!

Dr. David Fleming
09-10-2012, 12:09 AM

The 22zx came with a base engine 454 BBC at 310 horsepower and later the SBC at about the same power.

Second level engine was a 454 BBC at around 380 horsepower and later a 496 with about the same 390 horsepower.

Third level engine was a 502 BBC at around 415 horsepower and later a 496HO with about 425 horsepower.

A fourth level engine was advertized this was the Merc Racing 500EFI - to my knowledge no one has ever seen a 22ZX with this package.

Level one engines used a 24 pitch stainless steel BRAVO I prop - Level three engines used a 26 pitch stainless steel Bravo I prop. My own 22ZX uses a 30 pitch stainless but the engine is mildly tuned.

Early 22zx used a carburated engine usually with Webber/Carter 810cfm carburator. In aprox 1996 Mercruiser went to MEFI - Mercury Electronic Fuel Injection. This came in three or four versions MEFI I 1996 - MEFI II in 1997-8 - and MEFI III in 1999 to 2004. If I remember right later versions used the 500 series computor.

2005 Mercruiser went away from the old traditonal BBC to the entirely new V-8 engine the 496 in two versions. This only lasted until 2008 when GM went bankrupt and they dropped the new big V-8. Then Mercruiser went with the SBC. In the last few years Mercruiser has made their own BBC on the old 502 engine design so the 496 is a kind of orphan motor.

The Mercruiser wiring harness changed to a different type of connection 9 pin to 14 pin so after 2004 the early engines won't plug into later boat wiring without an addaptor.

Changing engine upgrades is fairly easy if you keep within the model year group of your old setup - best and easiest if an entire engine package with all the pullies, hoses, wiring etc. This kind of package is available on the internet or from various engine and marine builders.

Don't get the idea you can call Mercruiser and order the various parts to make an engine - the parts are not available and the individual part cost is beyond comprehension.

Take my 454 310 hp swap for a 502 415 hp swap. The 502 had a damaged engine wiring harness - it took 6 months and I only got the wiring harness because my engine builder had good connections with the Mercruiser factory.

I would call a builder like Tyler Crockett Marine Engines and tell him what you want to do - plan on $20,000 for the entire cost. Then plan on adding Trim indicators, external hydraulic steering and K-Planes which Donzi would have added with a big engine.

310 horsepower will get a 22ZX to 60 mph GPS/ 64 mph speedo. 450 horsepower will get a 22ZX to 80 mph GPS/ 85 mph speedo.

Donzi made around 4000 22ZX hulls in the ten or so years it was in production - the last 10 went to the US government. It is not a common hull and now that Donzi is out of production each one is more unique. Early hulls did not have a windshild or step hull and a few had a unique full size windshield from the larger Donzi.

Why don't you post a pic of your boat?

09-10-2012, 09:24 AM
I'm not sure where the 400 hour number comes from but that seems awfully low. I'd say the average for a performance boat that is taken care of and not ragged out is more like 800 hours.

The more recent engine life studies also point to fuel burn as the main indicator of engine life. Basically, the engine has a life span of however many gallons of fuel. So one that is running slower, burning less fuel, will last a longer number of hours.

This makes sense across the board. If you think of a car running the highway most of its life it will probably have a high number of running hours but relative low fuel burn. Take the same car at the drag strip a 1/4 mile at a time and it would have a high fuel burn relative to low hours.

09-11-2012, 04:29 PM
Why not turn it into a 383 400hp.bigger motor more weight.i have a 18 and a 383 carbed that i built last year for i say 4000 with the top being all aluminum heads intake and stainless exhaust 4".all in front of a blackhawk drive. works great.