REPLACEMENT OF 7.4 MPI WITH RAM JET 502

[screaming eagle]

IM WANTING A LITTLE MORE HORSE POWER FOR MY 2000 259 CHECKMATE CONVINCOR AFTER CHECKING SEVERAL ENGINE SUPPLIERS I SEE SEVERAL OF THEM OFFER THIS RAM JET 502,DONT KNOW IF IT IS A REAL MARINE ENGINE OR NOT,HAS ANYBODY MADE THIS SWAP AND WILL IT WORK IN MY BOAT AS A DIRECT REPLACEMENT? THANKS SCREAMING EAGLE

 

[vinny p.]

You are going to get different views on this. It has been discussed here a few times before. My thoughts and experiences on using any GM crate engine in a boat are not good ones. While the 502 Ram Jet is a real nice engine, for a car, the closest I would let it get to a boat, is in the tow vehicle that tows the boat to the ramp.
For the $10k + that GM gets for this engine, $2.5 k for CMI's, maybe $1k for miscellaneous rigging, you could most likely find a good used 525 BobTail take out or simply build yourself something from scratch designed for marine use. If 500 hp is your goal, getting it from a bog block is real easy to do.

 

[screaming eagle]

RAM JET 502

VINNEY WILL MY INJECTION OFF MY 7.4 FIT THE 525 AND CAN IT BE CHIPPED FOR THE DIFFERENCE IN CUBIC INCHES AND HORSE POWER? I HAVE A CUMMINS TO PULL IT TO THE LAKE. THANKS GREG

 

[vinny p.]

No, you need to get the fuel system that comes with the 525.

 

[Magnum Thunder]

Hey Eagle-​

Check out Lakeside Restorations link. Lots of engines to look at to get ideas. I have a 454 in my 25 Convincor it had a blower on it before I bought it. From what I'm told, it screamed! I bought the boat with out it. I would stay away from a crate engine.​

Magnum Thunder​

 

[screaming eagle]

502 FOR 7.4

THANKS GUYS I MAY JUST REBUILD MY 7.4 FORGED PISTONS AND A GOOD SET OF HEADS IF I DO THIS CAN YOU GUYS HELP ME WITH A CAMSHAFT,IM AN OLD DRAG RACER AND EVERYYHING IS TOTALLY DIFFERENT,ALSO WHO CAN REPROGRAM MY COMPUTER TO DO UPGRADES LIKE I WANT TO DO?ALL THE GUYS AROUND TULSA SAYS TO THROW THE INJECTION AWAY AND INSTALL A CARB.

 

[ezstriper]

probably going to get a lot of opinions here on this but if you are trying add H/P and going to redo the engine I would loose the fuel injection in favor of a good intake/carb set-up...far cheaper and easier to tune, + you can sell the injection set-up...my .02 worth...Rob

 

[Lakeside Restorations]

Hey Eagle-​

Check out Lakeside Restorations link. Lots of engines to look at to get ideas. I have a 454 in my 25 Convincor it had a blower on it before I bought it. From what I'm told, it screamed! I bought the boat with out it. I would stay away from a crate engine.​

Magnum Thunder​

Thanks for the refferal..

Eagle,

You should be able to have your 454 redone & pumped up and still be reliable.. We can do this for you if you would like. I will say it is pricer than a street engine because of the way it is done & the components used. Also a good exhaust would be required. There are also a few chioces that we use regularly & sell as well. Such as CMI, Stainless marine & GIL...

I agree with Vinny & Thunder, you would be best off staying away from street engines. Unless you have the capabilities to convert them & reflash them yourself you will likley spend more time & money fooling with it to get a modded street engine converted right then you would just going a custom marine build to begin with..

Just my 2 cents.. If you should need our services feel free to give me a shout. Jamie / Lakeside


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[Magnum Thunder]

502 FOR 7.4

Jamie-

What kind of $'s could one expect to pump up a 454? Blower, better exhaust. I am thinking about a freshening up of my 454. I would like to build some horsepower out of it.

 

[Lakeside Restorations]

My answer is so cliche', but it really depends on what you want done & how far you want to go.. The sky is really the limit.. If you would like to give me a call I could briefly discuss some options with you.. Jamie / Lakeside 570-639-2628

 

[smallblockford]

alot of good comments from every one. car engines dont do well, a bobtail will definatly get it done it usually comes with everything you need to upgrade your boat. remember drives can cause problems. just like a car the drivetrain has to be beefed up to take the engine.

the first thing you need to do is figure out how fast are you realisticly trying to go, then figure out if you are financly capable, boats are expensive to get 10 mph out off, totally different from drag racing.

one opinion i have is blowers are awsome nothing like em, good exhaust great.

a good prop can meen the world make an undrivable boat drivable, make a boat crazy. you will see it more on a lighter boat as far as what it does for drivability but it does make major diffences.

a true blueprinted prop the right way can give you a free pitch of prop, no moter required.

good luck and this can be very expensive :cheers

 

[screaming eagle]

7.4 to ram jet

THANKS VINNY AND THUNDER FOR ALL YOUR GUYS HELP IT HASNT BEEN GOOD SINCE THE OLD DRAG RACING DAYS,IF YOU GOT A PROBLEM THERE WAS OTHER RACERS TO HELP YOU WORK IT OUT. VINNY WHAT KIND OF SPEED DO YOU GET OUT OF YOUR BOAT? MY STOCK MOTOR IS PUSHING MINE AT 64 BY GPS,I WOULD BE HAPPY WITH 75. IM VERY GOOD AT BUILDING MOTORS FOR RACE CARS BUT BOATS ARE A DIFFERENT,WHEN I GET STARTED IVE GOT TO HAVE THE BEST OF THE BEST OR I WONT DO IT THE HALF ASSED WAY SO I DONT HAVE A IDEA WHAT A BOAT MOTOR NEEDS. I GUESS ILL MAKE THAT PHONE CALL BUT I WOULD REALLY LIKE TO KEEP THE INJECTION.ITS BAD TO BE 55 AND STILL A NEED FOR SPEED. THANKS GREG

 

[vinny p.]

Gregg,

I can run 83 any day, 85 on a good day. If you choose to build an engine, I can help you pick the right parts. If you have experience building drag race engines, you can build a marine engine. Assembly is still the same, you just have to pick the right parts. I too started out with drag racing. For many reasons, I switched to boats several years ago. I still crew ( part time ) for a friend who runs a Comp Eliminator car. I enjoy going once in a while, but boats have become my passion.

Remember, as was said, boats are simliar to cars in just one respect. Depending on how much power you plan to add, you have to be sure your equipment can handle it. Your stock Bravo drive, small trim tabs, cable steering, etc. , if not gone already, all have to go. You will need to replace the entire fuel system, starting from the tank pick up. The stock Merc exhaust has to go as well.

 

[Lakeside Restorations]

Eagle, I still agree with the advice given here so far as well.. As far as if you are used to building engines, as Vinny said the assembly procedures for doing an engine build will be the same.. The Fuel systems on injection will operate a bit differently tho.. The Ram jet can be made to work, but it must be reflashed to work without an O2 sensor among some other things.. Also the cam is a little aggressive for a wet exhaust leaving possibility of reversion. There are also the considerations of marine gaskets & plugs to be used made with stainless & brass as opposed to most stock auto applications materials..

Long story short if you feel you have the knowledge to do a conversion & build yourself & dont mind tearing down a good part of a new crate engine the ram jet isnt a bad base to builf from if you want to have efi.. You would have a good ammount of good useable stuff to start with.. The problem is that by the time you get done both time & money wise you are still usually in the land of doing a start to finish build of an all out marine engine from scratch. The thing that is nice about a custom build is you can choose all of your internals etc base on what you like. Where as if you go with a crate you get what you get, unless you are buying for block & fuel system only..

Jamie / Lakeside

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[screaming eagle]

7.4 to 502 ram jet

VINNY I WILL TRY TO GET A PHONE NUMBER FROM YOU,THE ONLY THING IM PROBABLY GOING TO NEED IS HELP ON CAMSHAFT,BEEN OUT OF DRAG RACING 10 YEARS AND STILL IN MY BLOOD,SUPER COMP 67 CAMARO FOR 7 YEARS AND WORKED IN A MACHINE SHOP DURING THAT TIME AND STILL COULDNT AFFORD MY HABBIT,REALLY ENJOY BOATS NOW AND IT KEEPS ME AWAY FROM THE STRIP.GREG

 

[vinny p.]

Jamie,

Along with others here, I respect your input on your posts. It is not often, you will find a person who is " in the business" and is offering free advice to people.

I am certainly not disagreeing with you, but I was unaware of a remapping for that ram jet 502 that would eliminate the O2 sensor. Would you still use the factory ECU? Wouldnt it be feasable and more recommended to just use a wide band O2 sensor in the header? I have an Innovate wide band O2 in my CMI's, with a guage on the dash. I am running a primitive but still very functional Dominator on my 540. Naturally, the 02 doesnt regulate the fuel mixture, it is just for me to monitor as I am running.

I feel that unless the mapping of the injection system is done on a dyno by someone you really trust, I would not feel safe. Call me old school, but I feel that complicating things by having a fuel curve that you cant easily change is not ideal. I would prefer the systems that allow you to perform your own tuning with a laptop.

 

[vinny p.]

Gregg,

Keeping away from the drag strip can be a good thing. So, you ran Super Comp, not a bad class to run. I just never liked slamming on the brakes, then watching your opponent blow by you and take the win light. Gotta hate when that happened. Unusual to have a door car, especially 10 years ago, compete in a class dominated by dragsters. In fact, dragsters still dominate it. When you are ready to talk more, PM me your # or I can PM you mine.

Where are you located? Do you boat in fresh or salt water? As Jamie said, crate motors are not set up for salt. Then again, nothing can take salt for very long. The only good thing about salt water is the ocean and the lack of Quagga and Zebra mussels. Seeing an occasional whale, seal, turtle, shark or dolphin is pretty cool too. Unless you happen to be swimming!!

 

[screaming eagle]

7.4 to 502 ram jet

VINNY TULSA OKLAHOMA,WE BOAT ON GRAND LAKE WHITCH IS A MEGA BUCK LAKE WHAT EVER YOU GOT ,SOMEONE WILL BE BETTER NEXT WEEKEND,THEY HAVE MILLIONS OF DOLLAR HOUSES ITS THE ONLY LAKE IN OKLAHOMA THAT YOU CAN BUILD ON THE WATER AND PEOPLE COME FROM EVERYWHERE TO BUILD ON THE LAKE,MERCRUISER HAS SOME SUPER FAST BOAT HID UP THERE ON HARBORS VIEW MARINA THATS ON A LIFT AND COVERED SO YOU CANT TELL WHAT IT IS ILL GET YOU MY NUMBER SOON. I KNOW WHAT YOU MEAN ON THE S/C CLASS THAT IS THE MAIN REASON I QUIT,ITS HARD TO WIN IN A DOOR SLAMMER CAR UNLESS YOU GOT TONS OF BUCKS OR HAVE BICKLE BUILD YOU A LIGHT ONE,AND HERE THEY DONT PAY ****,DID A COMPLETE REBUILD ON THE TRACK AND NOW HAVE IT AN IHRA TRACK,THANKS ILL BE GETTING WITH YOU SOON. GREG

 

[Lakeside Restorations]

Jamie,

Along with others here, I respect your input on your posts. It is not often, you will find a person who is " in the business" and is offering free advice to people.

I am certainly not disagreeing with you, but I was unaware of a remapping for that ram jet 502 that would eliminate the O2 sensor. Would you still use the factory ECU? Wouldnt it be feasable and more recommended to just use a wide band O2 sensor in the header? I have an Innovate wide band O2 in my CMI's, with a guage on the dash. I am running a primitive but still very functional Dominator on my 540. Naturally, the 02 doesnt regulate the fuel mixture, it is just for me to monitor as I am running.

I feel that unless the mapping of the injection system is done on a dyno by someone you really trust, I would not feel safe. Call me old school, but I feel that complicating things by having a fuel curve that you cant easily change is not ideal. I would prefer the systems that allow you to perform your own tuning with a laptop.

No, I should have elaborated futher.. Sorry..

If he was going to run headers & wanted to NOT run the o2's or run a set of manifolds without o2 taps he would have to delete the o2 from being monitored in the mefi ecm that he would use with the ram jet.. Also he would ideally want to change the cam to use it in a marine environment therefore making it good to do a reflash anyway.. Without it the engine wont run, or wont run well & could have damage..

That aside yes you are absolutely correct, the 02 sensor will allow the fuel delivery to be as precise as possible & is a nice option to have.. However many just dont use it, many times because of the cost thinking or planning out required to do it..

I do agree if he doesnt mind spending some extra bucks that CMI or SM with O2 ports close to the base of the riser as possible to keep the o2 as far away from water as possible would be best. But he should still have the mefi system reflashed & use a cam that wont be as likley to have reversion issues..

The only other way to help cut downon that chance of reversion is to run 02 bunged dry exhaust, but still the cam is more of a street duty cam as opposed to a marine duty cam which is what he needs.. He will need the torque to come on from idle or just off of idle and stay there, the HP is important, but not as much so as the torque & the torque being there throught the majority of, or all of the useable RPM range as much as possible..

I hope this helps you guys a bit more to understand where I was coming from.. Sorry for any confusion..

Jamie / lakeside

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