Mercruiser 454 question

[Dstyles75]

I bought my boat used last summer. It came with a stock mercruiser MCM 7.4 litre bravo 454 in it. The advertisement said it only has 300 horsepower, I figure it probably has closer to 310 or 315 judging by other ads for boats with the same engine.

My question is; what determines the horsepower difference of engines with the same cubic displacement. Would it be possible to basicly turn my 454 into a 454 MAG by buying new parts or is the magnum a different block all together. And lastly how can I increase the horsepower of my stock engine without having to add a blower or supercharger. Thanks

 

[mkhammer]

I bought my boat used last summer. It came with a stock mercruiser MCM 7.4 litre bravo 454 in it. The advertisement said it only has 300 horsepower, I figure it probably has closer to 310 or 315 judging by other ads for boats with the same engine.

My question is; what determines the horsepower difference of engines with the same cubic displacement. Would it be possible to basicly turn my 454 into a 454 MAG by buying new parts or is the magnum a different block all together. And lastly how can I increase the horsepower of my stock engine without having to add a blower or supercharger. Thanks

Your engine is a low compression model with peanut port heads and a mild hydraulic flat tappet cam. It also has cast pistons a cast Iron crank and rods. The block is the same as a mag.and can be built up with new Quality components.

MKHammer

 

[Dstyles75]

Your engine is a low compression model with peanut port heads and a mild hydraulic flat tappet cam. It also has cast pistons a cast Iron crank and rods. The block is the same as a mag.and can be built up with new Quality components.

MKHammer

Thanks Hammer. I was thinking of adding a heat exchanger to it which would probably cost me over a grand all said and done. I'm begining to think it might be better to wait until I need to repower and put what I want in it. I don't know I guess I have some thinking to do.

What would you do... Rebuild or buy new?

 

[Lakeside Restorations]

Im sure that either Myself or Hammer can get you more power.

Depending on how much power you really want it could go either way. Sometimes it is cheaper & better to repower. Other times if you are just looking for a nice boost over what you already have then there are a few options.

Here are a few from easiest to most intricate:

Exhaust: upgrade (better manifolds, or a set of headers)

Heads: Oval ports for better flow with good response in your rpm range in either cast iron or aluminum and with smaller chambers for more compression..

Cam shaft: a few different options here depending on how far you want to go.

Or a low boost supercharger.. However the engine must be currently in very good mechanical condition before even thinking of adding one. Also it would be advisable to not run higher boost levels as your application has cast internals..

If you do want to look into adding more power to your boat feel free to give me a shout.. Jamie / Lakeside

 

[Wowchad]

I have a great article scanned from Moore the BBC expert who says that our standard cast 330HP BBC are basically the same engines used in the old corvettes that put out 450 HP.
As Jamie stated all you need is a head / cam and exhaust swap for a very nice, safe bump in power.
You can very safely spin these engines to 5000 RPM (probably 5200) but I don't know if I'd add any boost to a cast bottom end.
Exhaust alone does wonders to the stock 454!
I've had two of those engines in boats and they respond well to out-of-the-box upgrades.
Shoot me your email if you'd like a copy of the article. Chad

 

[Lakeside Restorations]

One of the nice things about exhaust kits is you also shed a good ammount of weight in the back of the boat in addition to picking up some power.. We sell & install quite a bit of systems.. They are also one of the safest power upgrades.. Jamie / Lakeside

 

[mkhammer]

I disagree with that article for the reason that the most Marine engine failures I have seen is from people trying to hot rod a engine with cast internals . I had a customer with whipple's on twin 375 hp. 496's with the low boost 3.5 system for this engine and broke a piston in one engine,Guess what he had to rebuild them both, I had a customer with a 454L with cam,heads,intake and header upgrades that I didn't do. It threw a rod with only 100 hrs on a well maintained engine because it ran too good.
The list goes on, sure you can do it but it will be short live if you drive it hard. That's why they upgrade to drive it hard.
A boat sees sustained high rpm for miles on end. Try to drive that corvette at 5200 rpm for 10 miles without shifting gears time after time it will blow up I guarantee it.
Further more a marine engine is not the same as a car engine. Though they share alot of the same components the machine work is quite different. If you want it to last you have to use good components. You can't put a high performance top end on a BBC and expect a stock cast iron lower end to handle it. As mentioned it's cheaper in the long run to pull the engine and do it right with a performance rebuild.


MKHammer

 

[mkhammer]

One of the nice things about exhaust kits is you also shed a good ammount of weight in the back of the boat in addition to picking up some power.. We sell & install quite a bit of systems.. They are also one of the safest power upgrades.. Jamie / Lakeside

I agree this is the only safe upgrade for that engine.



MKHammer

 

[Lakeside Restorations]

I disagree with that article for the reason that the most Marine engine failures I have seen is from people trying to hot rod a engine with cast internals . I had a customer with whipple's on twin 375 hp. 496's with the low boost 3.5 system for this engine and broke a piston in one engine,Guess what he had to rebuild them both, I had a customer with a 454L with cam,heads,intake and header upgrades that I didn't do. It threw a rod with only 100 hrs on a well maintained engine because it ran too good.
The list goes on, sure you can do it but it will be short live if you drive it hard. That's why they upgrade to drive it hard.
A boat sees sustained high rpm for miles on end. Try to drive that corvette at 5200 rpm for 10 miles without shifting gears time after time it will blow up I guarantee it.
Further more a marine engine is not the same as a car engine. Though they share alot of the same components the machine work is quite different. If you want it to last you have to use good components. You can't put a high performance top end on a BBC and expect a stock cast iron lower end to handle it. As mentioned it's cheaper in the long run to pull the engine and do it right with a performance rebuild.


MKHammer

Couple things.

1. I 100% agree that forged internals are the best & safest way to go, and building something from the ground up with a specific purpose & design for big safe & reliable power with a long life is also the ideal way to go. It also costs time & money to do so. This unfortunatley is not always an option financially for some..

2. Im not looking to call you out, but Whipples standard low boost kit for the 496 runs at 5-6psi. So unless it was speciall ordered with a 3.5 pulley for some odd reason, set up incorrectly or running at some other altitude than set up for (again set up wrong) I am not sure why the whipple would be at 3.5 psi...
The ATI/Procharger system's low boost kit is 3.5 psi. Possibly you are thinking of this kit instead..

Also as far as the procharger compared to the whipple, You cant even compare the 2 systems for that engine. The whipple wins hands down..

The procharger works, but is crude & nowhere near precise enough in my opinion to be reliable long term without doing mods & increasing the precision of fuel delivery, spark etc..

The whipple already does that if you set it up right & can be reliable with some other add ons.. Been there done that, more than once including on one of my own engines. But again not greedily & I spent the time to fine tune everything..

Beyond that, If some one just wings something on there & doesnt check it, then it is asking for trouble. Or if they abuse it, it is asking for trouble..

Again no doubt building an engine for scratch with all of the ideal parts from the get go is the ultimate way to go, whether it is natrually aspirated or supercharged. I'm just saying that when done within reason that there are sometimes other options to get some more power. Some of those options are better than others & sometimes after a certian point you are just better off financially building a new power plant from scratch..

I probably should have clarified some of this a little bit more in my earlier post.. Jamie / Lakeside

 

[mkhammer]

Couple things.

1. I 100% agree that forged internals are the best & safest way to go, and building something from the ground up with a specific purpose & design for big safe & reliable power with a long life is also the ideal way to go. It also costs time & money to do so. This unfortunatley is not always an option financially for some..

2. Im not looking to call you out, but Whipples standard low boost kit for the 496 runs at 5-6psi. So unless it was speciall ordered with a 3.5 pulley for some odd reason, set up incorrectly or running at some other altitude than set up for (again set up wrong) I am not sure why the whipple would be at 3.5 psi...
The ATI/Procharger system's low boost kit is 3.5 psi. Possibly you are thinking of this kit instead..

Also as far as the procharger compared to the whipple, You cant even compare the 2 systems for that engine. The whipple wins hands down..

The procharger works, but is crude & nowhere near precise enough in my opinion to be reliable long term without doing mods & increasing the precision of fuel delivery, spark etc..

The whipple already does that if you set it up right & can be reliable with some other add ons.. Been there done that, more than once including on one of my own engines. But again not greedily & I spent the time to fine tune everything..

Beyond that, If some one just wings something on there & doesnt check it, then it is asking for trouble. Or if they abuse it, it is asking for trouble..

Again no doubt building an engine for scratch with all of the ideal parts from the get go is the ultimate way to go, whether it is natrually aspirated or supercharged. I'm just saying that when done within reason that there are sometimes other options to get some more power. Some of those options are better than others & sometimes after a certian point you are just better off financially building a new power plant from scratch..

I probably should have clarified some of this a little bit more in my earlier post.. Jamie / Lakeside

First off you are preaching to the quire

The Kit was on the boat when it was brought to me and it was verified by Whipple to be a 4.5 psi kit I was thinking 4.5 but wrote 3.5 may of had Procharger on the brain.
So regardless I'm not sure what point you were making that is even more boost. They also said the 5 psi kit was for the mag HO.
But here we are and I am only telling my point of view and what I have had great results with and that is a forged rotating assembly regardless of blower system.
I would not recommend a hypereutectic piston with supercharging either.

First a guy on limited funds he is shooting himself in the foot supercharging a cast internal engine. I would recommend up grades but supercharging is not one of them. I'm not saying you are but If you do recommend supercharging with cast internals that is your business.
Where these kits are available people will try it and engine failure will follow.

As for a Whipple compared to a pro charger I was not comparing the two.
I have alot of experience tuning prochargers and it's a whole different program.
I think the procharger is a good system for the recreational boater.

Prochargers are less expensive than a Whipple and they are quality units. Procharger holds the 2002 APBA championship OUTLAW PERFORMANCE 1 with M3 units.They didn't achieve that by breaking and the engines failing. Anybody will have trouble with any blower if it isn't set up right.
The facts are procharger produces the coolest charge air temp. easier on your drive and a 3-year warranty. whipple chargers make massive amounts of torque at low rpms and will snap things alot faster than a procharger that builds boost with rpm. I don't have anything against whipple chargers. But for a recreational boater that can't afford repairs. Their drives will last longer and I have seen over 250 hrs of operation without fail. This is the way to go on a budget. The testimonies on our web site speak for their self. I have a friend that has a Whipple charged force cat that blew up 2- XR drives and 1- b-max drive A few summers ago and now is running a IMCO sc with no problems so far. I couldn't afford that myself. I enjoy driving my boat a little more than working on it. Remember the old saying (how fast do you want to spend) prochargers work good too ,easy to tune a carb setup and a efi should be tuned real time not by mail order.

A procharged 36' cobra won the 2003 apba championship outlaw performance 1 class with 540 c.i. M4 at 1375 H.P they beat all other supercharged boats in their class whipple's included. This adds up to reliability and consistency for procharger. procharger offshore champions two years in a row and four runner ups. This was a few years ago but they made a statement.

Whipple has their championships too more recent and I agree they have killer systems.

Tuning is everything for any system to work right.


MKHammer

 

[mkhammer]

Jamie,
I know you are a knowledgable person and good at what you do. What you have had success with I may have not.
In whole I feel we are on the same page and I know you don't give bad advice.
I'm a pretty conservative guy. But.........
I still like the looks of a polished 1471 with dominators on it.


Mike

 

[Big Red]

The best thing to do is leave your engine alone thats in the boat. Buy yourself another engine and build it on the side. For all the aggravation you will go threw doing some head work and a cam change its no worth it.

If you take your time and shop around you can get good deals on parts. You need to decided a speed number for your goal. And their will be enough people on this board that can tell you what the ballpark figure in HP and torque you will need to achieve your goal.

Cubic inches is the only way to go

 

[Dstyles75]

Thanks for all the input guys. Here's what I decided to do for the moment. It still has that stupid quick and quiet exhaust in it so by taking that out I should gain something. That would be good time to put some performance exhaust manifolds and risers in it. We'll see what that does for power. That may be all I'm looking for. Again I use this boat in Long Island Sound which rarely sees conditions less than one to two feet and three foot is not uncommon. 80mph in a 22ft convincor in three foot swells is probably something I shouldn't be trying for. I would be happy with a 5mph increase. I think buying new would be better than rebuilding but I'm still paying on the boat. I can't justify replacing a perfectly good engine with only 300hrs on it. Again, Thanks for the input and I'll keep you all posted on the result.

 

[Lakeside Restorations]

Jamie,
I know you are a knowledgable person and good at what you do. What you have had success with I may have not.
In whole I feel we are on the same page and I know you don't give bad advice.
I'm a pretty conservative guy. But.........
I still like the looks of a polished 1471 with dominators on it.


Mike

No problem.. We are on the same page for the most part, I just have a few of my own opinions that differ a little bit based on what we have seen & what brands we like the best in my shop.. The good thing is that we agree on the more important stuff, like doing things right & telling the customer important pros & cons on what they are looking to potentially do. Jamie / Lakeside

 

[mkhammer]

Thanks for all the input guys. Here's what I decided to do for the moment. It still has that stupid quick and quiet exhaust in it so by taking that out I should gain something. That would be good time to put some performance exhaust manifolds and risers in it. We'll see what that does for power. That may be all I'm looking for. Again I use this boat in Long Island Sound which rarely sees conditions less than one to two feet and three foot is not uncommon. 80mph in a 22ft convincor in three foot swells is probably something I shouldn't be trying for. I would be happy with a 5mph increase. I think buying new would be better than rebuilding but I'm still paying on the boat. I can't justify replacing a perfectly good engine with only 300hrs on it. Again, Thanks for the input and I'll keep you all posted on the result.

I apologize for getting off topic,
Since you are not worried about speed and just want to wake it up a bit.
My recommendations is to add a good exhaust system and leave it alone and enjoy the boat.
Imco powerflow exhausts work well and you will feel a power gain from them over the stock exhaust.
If you ever do decide to upgrade your engine You will already have a good exhaust system to run on your new engine.


MKHammer

 

[Lakeside Restorations]

Thanks for all the input guys. Here's what I decided to do for the moment. It still has that stupid quick and quiet exhaust in it so by taking that out I should gain something. That would be good time to put some performance exhaust manifolds and risers in it. We'll see what that does for power. That may be all I'm looking for. Again I use this boat in Long Island Sound which rarely sees conditions less than one to two feet and three foot is not uncommon. 80mph in a 22ft convincor in three foot swells is probably something I shouldn't be trying for. I would be happy with a 5mph increase. I think buying new would be better than rebuilding but I'm still paying on the boat. I can't justify replacing a perfectly good engine with only 300hrs on it. Again, Thanks for the input and I'll keep you all posted on the result.

If you are looking for only a little bit then your safest & best bet (especially in your boating waters & your boat's size) is probably first going with a performance exhaust kit.. Jamie

 

[Lakeside Restorations]

First off you are preaching to the quire

The Kit was on the boat when it was brought to me and it was verified by Whipple to be a 4.5 psi kit I was thinking 4.5 but wrote 3.5 may of had Procharger on the brain.
So regardless I'm not sure what point you were making that is even more boost. They also said the 5 psi kit was for the mag HO.
But here we are and I am only telling my point of view and what I have had great results with and that is a forged rotating assembly regardless of blower system.
I would not recommend a hypereutectic piston with supercharging either.

First a guy on limited funds he is shooting himself in the foot supercharging a cast internal engine. I would recommend up grades but supercharging is not one of them. I'm not saying you are but If you do recommend supercharging with cast internals that is your business.
Where these kits are available people will try it and engine failure will follow.

As for a Whipple compared to a pro charger I was not comparing the two.
I have alot of experience tuning prochargers and it's a whole different program.
I think the procharger is a good system for the recreational boater.

Prochargers are less expensive than a Whipple and they are quality units. Procharger holds the 2002 APBA championship OUTLAW PERFORMANCE 1 with M3 units.They didn't achieve that by breaking and the engines failing. Anybody will have trouble with any blower if it isn't set up right.
The facts are procharger produces the coolest charge air temp. easier on your drive and a 3-year warranty. whipple chargers make massive amounts of torque at low rpms and will snap things alot faster than a procharger that builds boost with rpm. I don't have anything against whipple chargers. But for a recreational boater that can't afford repairs. Their drives will last longer and I have seen over 250 hrs of operation without fail. This is the way to go on a budget. The testimonies on our web site speak for their self. I have a friend that has a Whipple charged force cat that blew up 2- XR drives and 1- b-max drive A few summers ago and now is running a IMCO sc with no problems so far. I couldn't afford that myself. I enjoy driving my boat a little more than working on it. Remember the old saying (how fast do you want to spend) prochargers work good too ,easy to tune a carb setup and a efi should be tuned real time not by mail order.

A procharged 36' cobra won the 2003 apba championship outlaw performance 1 class with 540 c.i. M4 at 1375 H.P they beat all other supercharged boats in their class whipple's included. This adds up to reliability and consistency for procharger. procharger offshore champions two years in a row and four runner ups. This was a few years ago but they made a statement.

Whipple has their championships too more recent and I agree they have killer systems.

Tuning is everything for any system to work right.


MKHammer

Mike, correct me if I am wrong, but I think that the boat that won that was not stock. I am rather sure that it had a custom fuel set up on it and is not exactly the same out of the box unit you put on a 454/502 marine big block.. It had a lot of time spent on it to make it right. It wasn't just bolted on.. The standard procharger kits have you tweak fuel pressure to keep enough "approximate" fuel in the engine when running. The Ecms are not reflashed by them, nor are there any sensors provided by them to reference boost to the ecm.. The whipple takes care of those missing items & calibrates the ecm to run it accordingly. The installer has to set up the sensors & pressures and other parameters to spec. Once that is done the whipple makes for a much more robust & reliable kit out of the box.

The boost temperature can be debated a bit on who's intercooler works better. Also as far as the popping drives, I have seen both units mash drives. A lot depends on the driver. The procharger can be a little easier on the drives when coming on to plane as they build boost more like a turbo (more gradual). The whipple as you said is more instant. This can hurt a drive faster if the drive is too aggressive. However when either unit is making big power & the boat gets the drive airborne you run the risk of potentially doing drive dammage if you arent ready to ease up.. A big HP Natrually aspirated engine can also cause drive problems driving aggressivley too.

As far as what I was talking about in regards to the boost differences is that the whipples kit allows for more boost, more reliably on most engines. Even the 496.. I agree that cast &^ Hypertectics are not the ideal parts for big power or SC units. However it has been done on them within reason & many of them have lived well IF set up right. There have been many done on the 496 (and I will be the first to admit that the 496 is not as good of an SC candidate as some other engines are) & they have lived. From what I have seen the engines seem to hold up better with a stock Whipple kit over a stock Procharger kit. I also belive the reason that that is, is because of tuning & one being more precise than the other out of the box. If you spend the extra time & $$$ to make the upgrades to the procharger kit's then YES they are much more reliable & easier on the engines as well.. Also on the earlier stuff like the earlier SB mpi's & 454/502 Mpi's the parts inside of them were better from the factory & they were more tolerant of boost delivered with a more crude form of spark & fuel delivery..

I have sold & installed many different blowers. I think the easiest to tune is a roots blower with a pull thru carb. I am not personally fond of blow thru carbs.. My favorite stuff though is EFI, but it usually gets much more expensive.

I think what we (you & I ) are now bantering over in a friendly manner is probably more about our personal tastes & personal vendor preferences.. Hey some guys like Coor's some like Bud, others like Heineken..

Jamie / Lakeside

 

[mkhammer]

Your right those boats were highly modfied that won championships with prochargers.If tunning was a issue they wouldn't have won. They dialed in a winning combination and stayed consistant and won. My point is they work and make big dependable power when set up right.
A Procharger is half the cost of a whipple for a stock kit and ATI answers the phone every time you call. Yes you have to know how to set them up.
It's hard to get through to whipple they don't answer their phone alot.
Whipple is a clean kit they had their problems too in the past.
I like them all.
I still won't install a kit on a cast internal engine. My customer that had one engine go bad from supercharging,(regardless of make) I had to rebuild both so he had matched quality rotating mass. The bad part about it the one block was damaged so bad it coudn't be used.
I'm not complaining it was a good job for me and expensive for him.

I will drink any kind of beer as long as your buying


So I agree with everything you say

 

[Wowchad]

Dstyles75 another thing to keep in mind is resale. For most buyers an untouched stock engine is worth more than a no-name built up one. (Even if a reputable builder built it you may still loose resale in most, average buyers minds)
If you only do exhaust and then plan on selling you can either swap the stock exhaust back on or assure your buyer that's all you did to it.

The article from Dennis Moore I was talking about points out that if GM was confident enough to build thousands of the L-36 BBC engines in the 60's and 70's with 390 HP and offer a full warranty then with the upgraded parts of today you can safely bump the HP up to around 400HP on these cast engines without premature failure.

Someone once told me that as a general rule of thumb on a stock engine if you increase the HP by 10% / 20% / 30% you decrease the reliability by that same 10/20/30%. Either way I personally wouldn't boost a cast engine. Chad

 

[wca_tim]

Dstyles75 another thing to keep in mind is resale. For most buyers an untouched stock engine is worth more than a no-name built up one. (Even if a reputable builder built it you may still loose resale in most, average buyers minds)
If you only do exhaust and then plan on selling you can either swap the stock exhaust back on or assure your buyer that's all you did to it.

The article from Dennis Moore I was talking about points out that if GM was confident enough to build thousands of the L-36 BBC engines in the 60's and 70's with 390 HP and offer a full warranty then with the upgraded parts of today you can safely bump the HP up to around 400HP on these cast engines without premature failure.

Someone once told me that as a general rule of thumb on a stock engine if you increase the HP by 10% / 20% / 30% you decrease the reliability by that same 10/20/30%. Either way I personally wouldn't boost a cast engine. Chad

the point on the comparisons with the l-36 is well taken, but i doublt many people drove those the way I drive a boat some days... As mentioned above, run that vette at 5200 rpms for hours, but put a sled of logs behind it to mimic the load the engine sees... the bearings and other internal components will very likely let loose on a much shorter time frame... at least in my experience / opinion...