View Full Version : engine rebuild????????????????????

doubleduece donzi
11-27-2011, 06:16 PM
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?

11-27-2011, 07:00 PM
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
11-27-2011, 07:44 PM
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
11-27-2011, 08:53 PM
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
11-28-2011, 07:43 PM
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!!!!!

11-28-2011, 08:16 PM
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
11-28-2011, 08:42 PM
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
11-29-2011, 06:39 PM
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
11-29-2011, 08:39 PM
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
11-29-2011, 08:48 PM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

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
11-29-2011, 08:53 PM
[ 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.

11-30-2011, 02:23 PM
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
11-30-2011, 05:08 PM
[ 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!

12-01-2011, 12:53 PM
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
12-02-2011, 12:58 AM
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!69012690136901469015690166901769011

12-02-2011, 01:00 PM
How many hours on it? :hyper:

Dr. David Fleming
12-02-2011, 04:10 PM
Yah, Tyler is the man to tune - and on a stock cam - heavy valve train was always the weak link in the big Chevy engine so went all Crane Cam parts. I think the porting job and the Inconell valves were a big improvement towards the 450 hp. Great heads to start with and they only got better - CMI e-top headers did give about 5 mph gps increase over the stock iron manifolds and weighed a lot less. Had to use the entire CMI exhaust system and mufflers as when the Corsa mufflers were still on the boat it seemed to revert a little water at idle. The 22ZX has that big iron engine pretty low in the water when not on plane.

The engine has 140 hours on it and boat has 500 hours - I did my hot rod thing with Tyler couple of years ago when she had 360 hours.

Cylinder heads are iron ones from 500 efi - off of race boat "Crazy Chicken" when they went to aluminum heads. CMI e-top headers are from another 500 efi and are off of race boat "Thunderstruck" when they went to tractor headers - just before Reiter was killed in that boating accident in NJ.

Shops like Tylers always got all that race equipment "take off" parts that surface when the racing rules change. Its a good way to get some great parts cheap.

doubleduece donzi
12-02-2011, 08:01 PM
Well i pulled the motor today.im going tom to see my engine builder and give him the motor.he says to stay with mpi for cost.god forbid my cuz's scarab beets me then next year will= procharger!!! However in my thoughts are that if my 22zx cant out run his boat with a new rebuild then a donzi aint what its worked up to be any way. We will find out thats a fact.damn you winter!!!!!!!btw thanks for all the help hawg and dr.

Dr. David Fleming
12-03-2011, 12:35 AM
DDD - Before you get too far here you need to know that marine engines use camshafts entirely different than automotive engines. For one thing the Mercruiser uses a roller cam and for the second thing, marine engines have serious water issues in the exhaust. This is because the exhaust is water cooled from inside by spraying water into the exhaust system just past the riser.

Marine cams close the exhaust valve at Top Dead Center and are different than auto engines that close the exhaust valve After Top Dead Center. Even good marine engines can suck water into the cylinders if things arn't right. Be sure your builder knows how to do marine engines and picks a marine cam.

The 22ZX is very fast - you are probably worrying for no reason. Unless your Scarab friend has a "step hull." Donzi 22ZX will probably be faster. The first Donzi 22ZX 1998 and before did not use a step hull, it used a regular "offshore deep V hydroplane hull." The "offshore deep V step hull" came out in 1999 and the back of the Donzi runs on air. For this reason it is fast, fast, fast.

You said your Scarab had a 454 TBI - Throttle Body Injection - which I never heard of. Only heard of 454 MPI - Multi Port Injection. The TBI injects the fuel like a carburator in the throttle area - the MPI has an injector for each cylinder near the intake valve - this means each cylinder can get its own diet of fuel. The TBI is sort of like a carb where some cyinders can run lean or rich.

All Mercruiser 454 engines since 1970's have all made about 310 horsepower in stock form carburator or fuel injection. So unless our Scarab pal has done some serious work on his 454 TBI and has a step hull I would think a good running Donzi could beat it easy.

Now about the propeller - this is a serious item and needs to be in first class shape - you can send it to B-Blades in Wisconson they tune all the racing props and have it "lab finshed" this will give you one fast prop. You should be using a Bravo I - four blade at 24 inch pitch.

The 22ZX can be a handful to drive and you have to keep the drive trimmed out and the tabs up and not crank the stearing too sharp at speed or it will spin out. Long as you remember this you should have no problems cause its a good boat.

Wear your engine kill lanyard when you go fast.

The Donzi stock speedometer made by "Gaff Rig" which is now "Livorsi" reads about 3 mph faster than the boat is actually going. You can get a hand held display that will give you the gps speed which is measured by Global Positioning Satellite which is pretty accurate.

Dr. David Fleming
12-03-2011, 04:13 PM
Marine cam timing is different than automotive cam timing - why?

Because the valve overlap is re-designed to keep water from entering the engine cylinders. The effective way to do this is to shut the exhaust valve before the intake stroke of the piston begins.

Take the Mercury Racing 500 EFI engine. One of the more successful racing engines. This engine uses Crane racing cam part number 169621 Grind number HR-292-25-14 IG

Intake opens 6.0 BTDC - closes 44.0 ABDC - max lift 109 - duration 230.0
Exhaust opens 57.0 BBDC - closes (1.0) BTDC - max lift 119 - duration 236.0

The unique cam spec here is the exhaust closing at (1.0) BTDC

1 degree Before Top Dead Center - no automotive cam would ever do this because so much more power is available by having the exhaust close around 10 degrees After Top Dead Center

This racing marine engine closes its exhaust valves before the exhaust stroke has been completed - read it and weep ladies. Keeps your big block alive and well in the wet.

Mercury 500 EFI is 502 cubic inches, produces around 475 horsepower has been widely used in APBA power boat racing for years and was also the premium engine of choice for larger off shore luxury hulls. Sometimes two or three engines graced the engine compartments of Cigarette, Fountain, Donzi, Baja, etc. Many driven by the young, the lovely, the desirable - bikini clad pilots across the azure blue waters of Florida to the state of Maine! Go figure.

The Hedgehog
12-04-2011, 12:11 PM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

Make sure your engine builder knows your efi is closed loop and not open loop. It will have to be reprogrammed. You can put all of the expensive parts in the world on it, without the proper cal, it won't run right.

doubleduece donzi
12-04-2011, 03:31 PM
Idk what is ment by the closed loop open loop..?..so since the motor is being rebuilt does that meen i will without a dout need to have some work or tuning done on the computer of the motor for lack of a better term?once again i really appreciate the feed back.

12-04-2011, 10:32 PM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

Dr D

To say that the exhaust valve is closed at 1 degree BTDC isn't quite true. The duration and timing of the cam you presented is taken at .050" lift. Multiply by the rocker ratio and you have the exhaust valve open .085" at the 1 degree spec. It will take another 30 or so degrees before it is fully closed. The so called advertised duration is a better predictor of the valve being fully closed. This is taken at .004" lift.

What makes this cam suitable for marine use, given the duration, is a fairly wide lobe seperation of 114 degrees combined with a 5 degree retard.


The Hedgehog
12-05-2011, 08:22 AM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

Yes. It will have to be reprogrammed. If your engine builder did not tell you that, I would use someone else. Better yet, don't say anything and see what he says.

Open loop EFI's have o2 sensors and tune themselves. Closed loop have a set calibration.

Young performance, pmefi, Crockett and a few others do it.

Once again, I will caution you about using someone without a marine background. The best car racing engine builder in the world may not be able to build a boat engine. If you do use someone without boat experience (and I am not talking about jet boat either). Make dang well sure a marine performance mech specs your cam, gives him critical tolerances and does the calibration!

Dr. David Fleming
12-05-2011, 11:06 PM
In designing modern engines the engineer is faced with the science of the job. Cam timing and related valve timing becomes a study of what is practical.

Crane cams gives the specification of pracitical valve events as a way of understanding what the camshaft and valves are effectively doing. In the real world though it becomes a study of Specific Time-Area of the valve opening event.

To work out any time-area problem, you must first be able to convert an engine's timing, in degrees into actual time at some given engine speed. Say a hypothetical exhaust valve timing of 170 degrees duration, and an engine speed of 7000 rpm - the speed at which it is intended that the engine should develop maximum power. To convert these known factors into time the following formula is used.

T= O/Nx6

Where, T is time, in seconds
N is engine speed, in rpm
O is the exhaust port open period, in degrees

Means, T=170/7000x6

T= .004 sec

Results of this mathmatical computation show that only .004 seconds are allowed for the entire exhaust passage event to occur at speed. The amount of gas flow through the valve at below .050 is negligable and the reason that Crane and others do not include it in their valve event specifications. For all practical purposes the Marine engine exhaust valve is closed at TDC. Unless you are considering gas flow in a hand cranked engine on an engine stand.

The Hedgehog
12-06-2011, 12:53 AM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

So, do you have a cal Dr Dr? I do!

12-06-2011, 06:00 AM
Cam may be a factor but the big factor is the exhaust system and how it deals with resonance which is the major factor in letting water work it's way back towards the motor. There was a post here recently where I found an article about an investigation in stock merc marine motors with high rates of reversion failures. Interesting read seems the riser were redesigned and they left a key design feature off. I just had a motor redone by a well known local car shop they have one guy who just deals with marine motors.

12-06-2011, 06:12 AM
Results of this mathmatical computation show that only .004 seconds are allowed for the entire exhaust passage event to occur at speed. The amount of gas flow through the valve at below .050 is negligable and the reason that Crane and others do not include it in their valve event specifications. For all practical purposes the Marine engine exhaust valve is closed at TDC. Unless you are considering gas flow in a hand cranked engine on an engine stand.

I think you need to stick to writing medical prescriptions.... your wayyyyyyyyyyyyyyyyyyyy wrong here

12-06-2011, 06:59 AM
Doc, Harvey Crane is given credit for the .050 standard, but not because the flow under that area is insignificant. With each company measuring from a different spot, advertised durations were oddly different on very similar cams. Crane used .004, Comp used .006 and SAE used .009. Combine that with how a roller is limited in accelerating the valve off the seat vs. a flat tappet and numbers were all over the place. Measuring duration at .050 gives everyone a better way to see the differences in specific cams vs. the "advertised" duration. The engine sees the valve overlap from seat to seat and it has a HUGE effect on how much power is made and where it is made. More overlap = less intake vacuum at idle = greater chance for reversion.

12-06-2011, 07:03 AM
Also, I don't think your formula allowed for the fact that the cam spins at half the crank's rate.

12-06-2011, 07:07 AM
Doc, I have a question for you > of the 4 valve timing events in a 4 stroke engine, what is the MOST important and why?

can you answer this without calling Tyler first?

12-06-2011, 10:00 AM
Here is a link to another thread that has some info on "resonance"reversion, and another link mattyboy posted that explains how exhaust design can help eliminate it.

12-06-2011, 10:40 AM
thanks Mike that's what i was looking for