engine rebuild????????????????????

[doubleduece donzi]

I bought a 1999 22zx 454MPI with a Bravo One outdrive and has a knocking motor....CHEAP! I'm having the motor rebuilt this winter. However, I have not ran the boat in the water, so i don't know what to expect performance wise with a stock motor. What is the average top speed with this stock set up? I would like to see 70 MPH, but I don't know how much to beef up the motor since I don't know what it will do stock. I'm tha guy with champagne taste and a natty light wallet, so I need to know the cheapest way to see 70 MPH. What mods should i make when rebuilding the motor?

[smokediver]

Cheap might be selling what you have and looking around for a low hour 502 .. Or you could rebuild what you have I think you will be real close .

[The Hedgehog]

What Smokediver said.

Look up RTGOGO's posts. He had that combo. I think that he got high 60's with the 454 MPI. If you want to run low to mid 70's, the cheapest route would be the 502 thing.

That or do some mods to the 454. To do it cheap, you will want to go carbed, bump up the cam a little, punch out the heads a little and go with a better exhaust. By the time you do that, you can do the 502 thing cheaper. If you are not used to spending money on marine exhaust parts etc, you can be in for a little surprise.

[Dr. David Fleming]

The guys are correct in what they say. Any speed costs money and you have to figure out what you can afford. Not only the engine but the rest of the package.

Easiest power up is a cheap Mercruiser 454 MAG MPI or 502 MAG MPI package these are often for sale on e-bay or can be had around at various marine service facilities - say $4000 to $6000. What is nice about this method is you get the entire package which will go directly into 454 MPI harness - easy quick and no brainer. The 454 MPI uses the same Bravo sterndrive as the MAG MPI engines so everything is just bolt up. Don't forget also, that each of these engines used a different pitch propeller. 454MPI used a BRAVO I 24p while the 454 and 502 MAG MPI used BRAVO I 26p or 28p. With a little tuning the 22ZX will pull a 30p prop and run close to 80 gps with the 502 engine.

Service life on all of these "stock engines" 454MPI or 454/502 MAG MPI is about 400+ hours so if you do serious hot rodding beyond this stock setup plan on this engine life getting much shorter. 502 on supercharger for example might get 100 hours engine life.

My experience with 22ZX speeds are as follows:

454 MPI runs about 63 mph speedo - 60gps
454 MAG MPI runs about 69 mph speedo - 65gps
502 MAG MPI runs about 75 mph speedo - 72 gps

this varies some with altitude, temp, state of engine tune and weight of load in the boat etc but these speeds are common.

Now you might ask what the difference is between the MPI engine and the MAG MPI engines?

The 454 MPI is a good fuel injected automotive engine from the GM truck line. This engine is also called the L-29 and uses cast iron crankshaft, small port heads and lighter duty connecting rods. A more mild camshaft. It is hard to turn this engine into the MAG MPI engine because you have to replace all the internal parts and a different fuel injection system. It does use the same engine block and exhaust system and attaches into the Donzi hull in the same way, but it also uses several slightly different brackets to hold on the various external accessories and it uses a different wiring harness for the fuel injection.

The MAG MPI engines are special Mercruiser designs using a common fuel injections system which, as I said, is different from the General Motors truck MPI. This MAG MPI fuelie system was designed for Mercruiser back in the 1990s by Linkenfelter racing. The other parts of the MAG MPI engine are heavy duty forged steel crank and rods and forged pistons with the large square port heads and a hotter camshaft.

As I said it is fairly easy to take the MAG MPI engine and put it into the saddle of a MPI engine and this is the cheapest easiest performance modification and is what Donzi did. Just be sure you get a complete MAG MPI engine setup with the wiring harness, engine controller, thermostat housing, etc. A complete engine package pulled from another boat.

Don't get the idea you can get these parts from Mercruiser to change one engine to the other - most of the stuff is out of production and the cost of parts from Mercrusier are absolutely outrageous!

Stock horsepower for various engine is as follows:

454 MPI - 310hp
454 MAG MPI - 385hp
502 MAG MPI - 415hp

These three engines can be hot rodded to extreme power but engine life and servicability are drastically reduced.

454 MPI will do 500 hp - cost $5000 to $10,000 or more

454 or 502 MAG MPI will to to 700 hp - cost $5000 to $10,000 or more

One last thing - the 454MPI uses an exhaust hose from the transom bracket to the sterndrive. The 454 and 502 MAG MPI use a short rubber exhaust stack and don't connect to the sterndrive.

Hope this helps,

[doubleduece donzi]

I will consider the mag and or 502 option. However, I have a pretty good connection with a damn good, and awesome engine builder! I will be pulling the motor myself this weeknd, so I'll find out just how bad the internals are. I am torn between staying with MPI or going to a carbarated setup. Part of me is saying just rebuild it stock with a little bigger cam and enjoy the boat. However, the other side is telling be since I have the SOB out and rebuilding it anywa, grow a set and say forget the cost. All that matters is bikinis, MPh, and B.A engine camming down at the dock at Lake martin, AL.. Hopefully you understand!i see no problem 400 out of this motor,oh and by getting 400hp i mean telling my builder hey i want 400hp !seing as the 502 (from what i read) is around the same shouldnt i expect around the same top speed from my 454 rebuilt at 400hp?I was told that bumping up the performance that much would require some work with the map or computer wich was said to be around 1500$.bottom line what do you guys think i could do with 400hp and should i stay mpi or go carbed?remimber $ depics wether i stay MPI or ect.Your info is greatly appreciated! THANKS!!!!!

[biggiefl]

2 things...1) I don't agree totally with the Dr., a stock 454 will last over 2,000 hours if treated right....not 400. A MPI is not your ideal setup due to the computer. Do a search here to find out that 400hp is pretty much not possible. A 454 rebuild is an easy 450hp engine if done right and will be under $4000 including everything. $10k means you bought it from Brunswick. I did my 330 up to 400hp running an Alpha for about $2k doing it myself and she lasted at least 8 years and more than 400 hours....like Flavor Flave says...Don't believe the hype!

[Dr. David Fleming]

I saw Tyler Crockett Marine take a 454MPI up hundred horse or so - injectors were too small and even though the remap of the computor was done she burned out a couple of new pistons. Ended up installing new bigger injectors and uping the fuel supply. Had replaced the crank and rods with forged parts - Crane Cams valve train etc. Not a lot of guys can map the computer short of being on the dyno and doing an open water calibration with an oxygen sensor. All this is going to add to the cost. Then you gota keep it running.

The carburator is a better and easier setup - not quite as fuel efficient but is somewhat self regulating - choices are out there for Holley, Webber/Carter/Eldebrock and good old Mercruiser GM quadrajet - single fourbarrel 750 cfm should give you 400 plus horsepower easy, even with small port heads - course you have to find the intake.

Another common hot rod trick is to add a supercharger like a Whipple to the stock 454MPI - this usually takes the help of an engine builder and the stock cranktrain won't take the abuse for long. Couple of nice packages to do this complete with all the instructions.

One thing I didn't mention before was the MPI fuel injection and ignition controller came in three generations

MEFI 1 - this mid 1990's controller did not have an internal schedule for supercharging the engine. Used on 454MPI and 454 - 502 MAG MPI

MEFI 2 - this later 1990's controller had the internal schedule and looked just like the MEFI 1 - used on 454MPI and 454 - 502 MAG MPI

MEFI 3 - 1999 and 2000 production - this controller had a much more advanced computer system and did not use the same wiring harness as MEFI 1 and MEFI 2 and was also used on 454MPI and 454 - 502 MAG MPI and is probably what you have got.

These controllers were all programable with a laptop computer if you had the program and could hook it up - fuel map and ignition timing plus entire diagnostic record - number of hours on boat and when and where sold.

MEFI - stands for Mercury Electronic Fuel Injection

cost of one of these controllers would shock you.

good luck with bad old donzi project,

[doubleduece donzi]

Well i guess im going to see what i can do with it! As of now i will be rebuilding the motor to 400 + hp and gettting rid of the mpi.i really hope im at 70mph. After all the trouble and $ i have been threw and will go threw with this boat if my cousins half rotten 22 scarab with (454 tbi) out runs me, i will be one mad ass.sick is more like it.basically im neverse becouse i dont kno what 2 expect.donzi's are seldom seen around here. I wish someone would come out and say hey i had 22zx around n/a hp with a n/a pitch prop and hit n/a mph.im in the dark since a cant run the boat to see what a stock motor delivers.i would also like some input on a good intake manifold for my setup.

[The Hedgehog]

Ok, now I am going to set a few things straight.

I have taken the 502 Mag MPI to 942 hp. I have done a few steps in between so I may know a little.

First of all, Dr D is closer to right. 2000 hours in a 454? Maybe in Crusader package in a cruiser running 2000 -3000 rpm. 500 hours is a good number in a Mag dressing. Can you get 700hrs? Sure, but you will have one tired engine for the last 200 hrs. That is just the way it is.

700hp in a 502 Mag? Not without a blower. The BEST in know of using the Lingfelter manifold was just over 650. That was stroked to 540 and the perfect combo. It literally took him years to crack that combo. Running N.A and stroked to 540, a more reasonable number is 615. That is heads, cam, extensive manifold work and a few days on the dyne with a good tuner. The best way to hit 700 hp is around 7 lbs of boost. Don't forget injectors. You can pull around 575 hp at 115 percent duty cycle. Start cracking 600 and you will need to step those up. I ended up with 65 lb injectors.

Basically a good na combo for a 502 mag is around 500 hp. That is punched out heads with inconel valves, properly speced cam, good exhaust and a reprogram. The reprogram should cost around $350. The tuned should spec the cam. More than that requires alum heads, extrude honed manifold, bigger injectors and a really good tune.

You can lever off a decent car engine builder, but they better know how to tolerance an engine for marine apps, how to spec a proper cam to have the right torque curve plus good hp without reversion AND how to program a mefi. Sure a good car guy can pull 700 hp from a 454 circle track engine, but it won't run worth a dang in a boat.

All above is why I mentioned just doing a recipe 502 or finding a stock mag motor.

[The Hedgehog]

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Actually A MEFI runs up to a MEFI 4. Merc used up to a 3. The 4 has better boost reference tables. The 1 and 2 will not map for boost. They are not all that expensive. I probably have a couple of 1's laying around that I would sell with a tune for $400.

Other than that, you had some great info!

[The Hedgehog]

[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

A 454 Mag MPI makes 385 hp. You can get it to 400 without much work. About all you will notice is a little better throttle response. Yes, if you want to make big difference, you will need to re-flash the ECU.

[biggiefl]

The more HP the less she will last...period. A stock 330/310 is a bulletproof engine and if treated right the hours can be in the thousands. A rule of thumb is if you run WOT a lot you will average about 20% of the life span. If you "could" run WOT 100% you would get about 10%. So if those who run hard hard are getting 400hours, 2000 is very possible. I have seen well over 3k on FWC cruisers. 400hp if you run it nicely can probably fetch close to 1000. My bud has a 502 EFI stock with almost 800 on it and she still runs the same speed as it did 15 years ago. I see the videos posted here and elswhere, amazed some of you guys get a season out your engines....then again some don't. People say an outboard is good for 1500 hours, I have a friend with twin 200Mercs that have almost 3k on each one, never been apart. I have seen 4 strokes with over 5k on them. All depends on how you treat it and how it is maintained. 90% of the engines I see being replaced are from bad manifolds/risers. I cruise a 2800-3k so I will let you know in 10 or 15 years how she is doing. Then again I bought used so who knows.

[The Hedgehog]

[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

First you say 2,000. Then it is 1,000. Then maybe 2,000.

We have Donzi's for the look, speed and sound. This guy is ready to blow off Scarabs, I don't think he is going to cruise at 28 mph.

I still stand behind 500hrs on a mag if you use it for the prescribed purpose.

Much more than that and you risk having an uh oh during boating season. That is bad indeed!

[biggiefl]

What I said was 2000 hours for a bone stock 330/310hp 454. 1000 hours for 400+hp. is very possible. 400/500 hours for us down here would be under warranty still for most....I don't think Mercury is that stupid. Hey if your main goal is to be faster than your bud, go big and pay big.

PS I cruise 35-38mph at that speed which in most areas is plenty. Maybe if I lived on some glassy lake I would have the need to go faster all day driving in circles looking to race but right now me and my chiropractor are content and I get about 4mpg.

[Dr. David Fleming]

Specs for Doubleduce donzi,

My 1999 22ZX step hull has the 502 MAG MPI - fully ported iron heads with inconel valves, stock crank, rods, block, stock cam, stock LInkefelter intake. Crane roller rockers, pushrods and roller tappets. CMI e-top headers - Tyler Crockett did the tune on the MEFI 3. Engine pulle 450 horsepower at 4800 rpm on the dyno.

External Latham hydraulic steering. Bravo I Lab finshed 30p four blade prop.

Runs 77gps to 79gps depending on the weather and the mood she is in. Runs about 1 mph gps slower with 28p prop and accelerates faster.

hope this answers your question!0620081344.jpg0620081344a.jpg0618081613.jpg0618081605.jpg0624081740.jpg0624081744.jpg0917102130.jpg