454/310 motor replacement options
 

I would like to pull this engine out and drop something more powerful in. What should I do?

Re: 454/310 motor replacement options
 

1st, what are your priorities, speed, durability, N.A., supercharged, does fuel economy play a role, what boat would you be installing the new motor in, new or used motor?

Re: 454/310 motor replacement options
 

How much do you want to spend? Are you willing to upgrade your drive as well? If not, you had better not go much above 500hp if you want to stay reliable.
There are a lot of builders that can build you an engine.
http://1800runsnew.com/ these guys seem to have a good reputation for a crate engine.

Re: 454/310 motor replacement options
 

The boat is a 97 baja hammer. I want more speed and power. Is the 500 a direct drop in? The 454/310 is just not strong enough. The drive is a bravo one and I want to keep it.

Re: 454/310 motor replacement options
 

The 500 should be a direct drop in, except maybe some changes for exhuast and the need for an electronic fuel pump. I think that's all.

Re: 454/310 motor replacement options
 

Are there any forum members dumping a 500 by chance.

Re: 454/310 motor replacement options
 

I'm currently switching from a 310hp 454 to a 502 EFI Magnum, I bought a complete engine with the fuel injection and everything and it will be pretty much a direct bolt in. Doing that swap should get you about 10 mph. I am also adding a procharger supercharger for some more added fun :D If you buy a used engine just be very careful who you get it from as there seems to be a LOT of shady deals out there. I bougt mine knowing it was in need of a rebuild so I didn't really have to worry.



Doug Schiller

Re: 454/310 motor replacement options
 

10mph more would be perfect. If anyone has a 502 please contact me at home 830 557 4270.

Re: 454/310 motor replacement options
 

Do yourself a favor and buy a long block 502 from www.1800runsnew.com I have two and they are great motors. All your accessories should swap over. If you have to have someone else do the work, it should not cost more than 1,000. Spend the money now, or you'll spend twice that later going used!!!

Re: 454/310 motor replacement options
 

Hi David:
I assume your 454/310 is a 7.4MPI? If so, you will likely have grief with the computer and injection system if you decide to build it up, or use the injection system on another built up short block.

My original power was a 7.4MPI...After I read about other problem stories both on here and on 'the other forum' with trying to get power out of these, I decided to repower completely.

I happened to luck into a 1999 HP500 carb engine at a good price, from a fellow repowering. Since it had 180 hours on it, I redid the top end. The bottom looked perfect.

Bob at Full Throttle Marine installed this for me about two months ago, in my 1999 Donzi 22ZX. I went from a best of 63 on a perfect day, with perfect chop, low gas and only me to 76.3 with half a tank of gas, at slightly under 5k rpm! (All GPS speeds). The cool part is that the 80mph Gaffrig II speedo is now PEGGED, straight down!! I haven't even played with props, yet, other than changing to a stock 28p Bravo with the new engine.

If you have a 7.4MPI, if I were you, I would look for a complete engine upgrade, with at least intake accessories. You will have fewer headaches, I believe.

Oh, as far as size, you should be able to fit almost anything into the space of the 7.4MPI, if that is indeed the engine you have. Only the 496 from what I looked into requires significantly more space. If you have through hull exhaust, then almost any will bolt right up! My HP500's Gils aligned perfectly with the stock through hull tips.

Best of luck with your decisions!
Kent

PS: Bob at FTM had a 7.4MPI that dropped a valve in his shop. I 'think' this motor was hotrodded, and the injection system was too lean, even though it was reprogrammed. I don't know the whole story, but I did see a piston in about a million pieces, chunks out of the block, and other major damage...The pistons are cast in the 7.4MPI...

Re: 454/310 motor replacement options
 

Oh, I forgot to mention....

Cdscarab mentioned a big question!! GAS MILEAGE!!

I used to be able to hot rod around this lake all weekend on 50 gallons. NOW, If I am into the throttles at all, I can almost WATCH the gas gauge go down!!

I was running hard (NOT at WOT) a couple of weeks ago, and burned up 50 gallons in about 2 hours!!!!!!!

There is a HUGE difference in gas consumption with horsepower!!!!

Take care,
Kent (Who needs a bigger gas tank now!)

Re: 454/310 motor replacement options
 

:D Yes, that was mine in pieces. I've only seen pictures of the inside though it's not a pretty sight!

Quick low-down on the engine. It was bone stock but had to come out for a coupler failure. While it was out........I wanted to add Corsa. While it was out, :D it got Corsa, plus significant head work including bigger valves, cam, injectors from an HP500EFI I believe (take outs from Tyler Crockett as he was programming the ECU) becasue the stock injectors weren't near enough, ECU programming and other little minor goodies. 2-3 tries at the ECU via long distance trial and error and it appeared to be about as right as it could be. It ran very good for about 60 hours and one very cool morning running just shy of WOT it dropped a valve and went boom! Valve appears to have stuck in the guide and of course the piston hit it and the rest is history....and I have the pictures. Rod with nothing left of the piston, a hole in the cylinder wall and a bent headless valve stem pearing out of the head.

Moral of the story is that Bob really, really wanted to rip the restrictive MPI off and go carb and manifold for both performance and reliability reasons since it would be sooo much easier to get the A/F right. I was stubborn and wanted to keep the MPI, not realizing just how resrictive it was and how much of a PITA it would be to get the ECU re-programmed right. Mid-range was awesome but top end pretty much died off over 4000 - 4200 RPM just like stock. I got 3-4 MPH more overall but that includes labbed and cupped prop at the same time. Lesson learned.

I would agree that if you want more power, repower and sell your 7.4 to someone needing to repower a small pocket cruiser that can use the reliable, flat torque motor. Otherwise, plan on spending a lot of money on head work, cam and CARB/MANIFOLD and get 400-425 HP. Not sure it's worth the $$$$ for that gain. The guy that bought my heads and cam will be doing the same thing to his (Volvo 7.4 GXi) but he's saving a ton of money buying my heads and cam so his will be more worth it.

We decided not to rebuild the 7.4 so Bob's building a 540 for mine right now. This one will be just a little more significant motor than the 7.4. :D

BTW, I still have pieces, I mean parts left from the 7.4 to sell!! :D

Re: 454/310 motor replacement options
 

Mudball, I see you are up in austin TX. I am right down here on lake McQueeney. We just had some big flooding down here alot of people lost boats. Did you do that swap yourself. If I buy s 502 could you help me put it in the boat? Oh yeah, my 454 is a carbed motor. No EFI.

Re: 454/310 motor replacement options
 

Sorry I see you had full throttle marine do the work. I was to tired to read all the post. Is that shop up in austin?

Re: 454/310 motor replacement options
 

Mudball, your right, a small gas tank can take some of the fun out of bigger power. My 21 scarab only carries 60gals. of gas which used to take me anywhere and back on this end of Lake Ontario. But after moving up to a Hawk 525sc, fuel load now plays a much larger part in planning a trip. Not that the 525 doesn't get good milage, it does, if I can resist playing with the power. Which I normally can't, way too much fun. But then that is why I went to the trouble of changing motors.

Dave Haag, one other thing you should do before driving that Hammer with +500 ponies. While the drive is off, have it checked by a reputable drive specialist. Repair and strenghten it where it needs it. Otherwise your new found fun could be short lived. I had mine checked by Chris Martin, Sterndrive Specialist, here in NY. It had about 400hrs. on it and would not have lasted the 1st weekend out with the 525 had I not had it rebuilt. I'm sure some of the guys on the board can direct you to some one in your area.

Re: 454/310 motor replacement options
 

I have the same need for reliable speed as David Haag mentioned above. My boat is a 1989 SeaRay 260 Cuddy (similar to the Pachanga) equipped with a 7.4L Carbed Merc 454 mated to a Bravo 1. The motor and drive are original with approx 790 hours. The entire boat has been well maintained and performs flawlessly, but I figure a repower is in order by this time next year. According to what I’ve read in this thread, it sounds like the best way to increase reliable power is to order a new 8.2L 502 rated at 435hp for approx $5k @ 1800runsnew.com and bolt on my intake, carb and accessories. Does anyone recommend an alternative or a different/new carb to install on this setup? Should I go MPI and where should I look to purchase the intake, injectors, wiring harness and computer? Following are pics of my boat and engine compartment. Thanks for all the help!
Dan

Re: 454/310 motor replacement options
 

Instead of your stock 7.4 intake. Find a Wieand Team G and a 800 Holley or a Mighty Deamon Marine 750. You will be much happier. Even a stock 454Mag intake is an alum high rise, that would be better than the 7.4 cast iron intake.
The Team G is what Merc used on their hi perf 454s like the 420.


I may have a 454 Mag intake for sale. PM me if intrested.

Re: 454/310 motor replacement options
 

I have a 2001 HP500 that I will be letting go. I think I have it sold, but if not, keep me in mind. I sold the boat it was going to go in, so I have no use for it. e-mail me offline at [email protected] if interested in more details. Don't worry, it's cheap... :drink:

Re: 454/310 motor replacement options
 

Madmax, I sent you email.

Re: 454/310 motor replacement options
 

I'm replacing my 454 Mag with a 496 HO. I thought about custom power but I don't want the headaches. I was also thinking about the gas thing too. I have a 60 gal. tank. With my 454 Mag I was averaging about 10 GPH. So, I could run about a 5 hrs on a tank. I figure the 496 will burn about the same fuel.

Re: 454/310 motor replacement options
 

SearayJim, I didn't know that was your engine over at FTM! It was amazing to see how a cast piston can disintegrate!

Full Throttle Marine is in Spicewood, Texas, just west of Austin on highway 71.

I highly recommend these guys to anyone. They know high performance marine. They are building SearayJim's new 540, too. The parts I saw for it are a thing of beauty!
=====
Yes, we have had major flooding too. They were just able to open the floodgates a couple of days ago at Mansfield. It will be several days before I can get to my dock again. It got so high that one of my anchor cables snapped, and the other one was super tight. It held though, thank God...

Yup, and the 2001 HP500 would be NICE!!
Just beware of the number of hours on these engines. While the bottom end is bulletproof, the cams are so hot in these that the valve springs go soft after 200-250 hours or so. The later EFI versions are supposed to be much better (won't likely break springs), but they still can go soft...

Take care,
Kent

Re: 454/310 motor replacement options
 

WOW!! I just read where you have a 525SC in a 21 Scarab, cdScarab!!!!!!!
Incredible!!

This board is fun!
Major power in small boats!!!

Kent

Re: 454/310 motor replacement options
 

Jig and David,
You are both prime for stroker kits. Take your existing engine, change the crank rods and pistons in the block with new stuff and boring the block to 4.310" will yeild 496 CID. The engine with the .250"more stroke will give you huge increase in torque which is what moves the prop, HP sells engines and is only a calculated number where torque is measured. I would think for around $3500 you could put a nice package together.

Chris

Re: 454/310 motor replacement options
 

cstraub69,
Where should I be looking to purchase or piece together a stroker kit as you described? Should I use the stock heads, but get them cleaned up and ported or other? I'm new to this and appreciate any assistance you can lend me.
Thanks!
Dan

Re: 454/310 motor replacement options
 

CDSCARAB,
What are you running for speed with that 525? Hows she handle?

Re: 454/310 motor replacement options
 

Dave & JIG .....I'm new on the forum here, and I'm really just a gear
head who's had a few boats and heard lots of stories : ). But, I've been
where you are at , and the moral of my story is you get what you pay for.
Cost VS. reliablility. Mercuiser or any reputable builder, builds the entire
engine top and bottom to withstand the level of hp/touque is was designed
for. In my opinion your best bet for a reliable headache free deal, is to go with
used or reman mercruiser longblock or complete engine with factory specs. Rather
than a cam here, heads there....etc. It may be more expensive at first but in the long run it pays off. Good luck to you. :drink:

Re: 454/310 motor replacement options
 

David Haag, give me a call and let's chat. I can probably get you sorted out. One option that I will have available this spring might be of interest. I am ordering a new boat for a customer. I am building a custom engine for it, but we will order it with an engine that will still be in the crate from Mercury. I can order it with any engine if someone wanted to chose. We'll sell the engine for what it costs us(very reasonable). A new 496 Mag HO might work really well in your boat. Can't beat the reliability. If you're(or anyone) interested I can work up a price. 830 6935591

Bob Lloyd

Re: 454/310 motor replacement options
 

Bob, I will call you tommorrow. You are an 830 prefix, where do you live? I am 830 as well here on lake mcqueeney. Whatever you suggest I am ready. We can discuss it tommorrow. Thanks for the response. Dave Haag

Re: 454/310 motor replacement options
 

Bob, I will bring my boat to you since you are real close. This sounds like its gonna work out perfect. Dave Haag

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David, Bobl is Full Throttle Marine in Spicewood!!

Howdy Bob!!

Re: 454/310 motor replacement options
 

I spoke w/Bob today and it looks like we are gonna do the hp500. I thought for a second since he has an 830 prefix it was his home number. Spicewood is not to far anyway.

Re: 454/310 motor replacement options
 

Sorry if this is a dumbazz question, but is an HP500 motor an 8.2L 502ci rated @ 435hp out of the box? Please advise.
Thanks!
Dan

Re: 454/310 motor replacement options
 

I believe the HP502 has 470hp were the 502 mag isthe one w/ less power ( 415hp ). I think the 496 is the motor w/435hp.

Re: 454/310 motor replacement options
 

I believe it goes something like this....490 MAG is 375 HP, 496 MAG HO is 425 HP, HP500 is 470 HP, HP500EFI is 500 HP and from there is' easy as HP525EFI is 525 HP etc, HP575 SCi is 575 HP etc. etc.

That's for stern drives and is PSHP not flywheel HP. V Drives, not that it matters, is a little different since it's a different drive thus different parasitic HP loss.

Re: 454/310 motor replacement options
 

I have plenty of room in my engine bay and would like to reliably increase the hp when I repower without having to spend a fortune. Is the HP500 motor carbed and will it bolt into the same engine mounts as my 1989 carbed 454? What is the engine of choice when it comes to staying carbed and naturally aspirated? Thanks again!

Re: 454/310 motor replacement options
 

Jig,
The dimensions are the same. You have a good base for repower. By adding a stroker crank and possible heads, you can build a "500 incher" for the boat. Eagle, Scat are companies with affordable kits, Probe is another. These kits can be had for around $1400 to $2K in parts. Freshen your heads or add a set of Merlin Oval ports with a mild roller cam and you can build your self an easy 500HP/600#/ft engine.

RMBuilder, Bob, is real good with combinations and would be able to assist you.

Chris

Chris

Re: 454/310 motor replacement options
 

Interestingly, all of the Merc Racing engines are crank rated HP.

The HP500 carb and HP500EFI both have 500 hp at the crank, 470 at the prop of a standard Bravo drive... Even the HP500 Bulldog (a 540 ci) is 500 hp at the crank...

The HP500 carb will fit like a glove in the place of a 454 carb or MPI, whether mag or not...

Chris: I believe these couple of guys want a 'factory' engine complete, as opposed to building one. At least that's my understanding...

Kent

Re: 454/310 motor replacement options
 

You learn something new every day. Just hope I can retain it!! :D

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Of course, everything I have ever seen shows Merc Racing to be very conservative in their hp ratings!

Heck, there's a fellow on another thread here who is upgrading his HP500, and with 270 hours on it, it showed 530+hp on the dyno!!(if you believe the dyno sheet, as it even had leaking head gaskets)...

The least HP I have heard of in an HP500 has been 515. The most was close to 550!
========
Hey SearayJim, how's your engine coming along??????
I sure would like to come over when Bob installs it!! That still blows my mind what you are doing to your little Searay!!!
========
David, did Bob tell you the story of our first test/debug run of my Donzi after he installed the HP500? I mean about the race we got in?

Kent

Re: 454/310 motor replacement options
 

Jigsaw89,
Nice boat you have there. However, I would be carefull when adding considerable power. Make sure your engine mounts can take the extra power and stress that goes with it. Also, I would check with somebody that knows high performance boats to make sure the stringer system and the integrity of the boat is suitable for what you are going to do. Remember, boats are unlike cars, it takes a considerable amount of power increase to see a few miles per hour. Good luck!