They weren't idling at 1300rpm. One was high that day because of a throttle cable issue. Once that was fixed I wanna say they were idling about 1000-1100 in neutral. And around 700-800 in gear . Actually, prob some of the nicest idling big blower motors I've seen, well carb wise.

These aren't truck motors with RV cams !!! Heck, mikes 1200hp 8 liter whippled carb motors idle at about 700 in gear. Mine sit at 1000 in nuetral and about 700-800 in gear also.

We'd be able to idle them down more if we were running some 23 mirage plus props . Would efi make them idle a little smoother, sure. im not sure i can swing the 8-10 grand to do the conversion so I won't have to give them a couple squirts in the morning....rootzefi has some nice kits for the roots blower setups. Not too bad at 6500 bucks a side ....:party-smiley-004:

Fountain Jeff has 900's with Bravos
Mike Tkach twin 950's with Bravos (cat)
My Cat had 900's with bravos
Dans boat would idle just fine with Bravos

All idled perfect, I dont mean to bud in my 2 cents because all I know how to do is spend money :)

You lucky SSM guys !!!

Thats it,,,,,Im shopping for a # 6 42 Tiger now LOL !!!

The jist of this whole discussion,,,,,, would I swap a good running carb motor to EFI,,,,probably not

Would I swap a EFI motor to carb,,,,,1000% nope !!!

believe it or not,im not getting in this pizzin match,but i will say the new fi setup,s like holley,s dominator are more tunable than a good carb,but the merc system on a 415 hp 502 is primitive at best,it has no o2 sensor,no barometric pressure sensor,and no capability to self tune.it is programed for the 415 engine and will run good in stock configuration,but must be reprogrammed if changes are made to the engine,and if you live in florida and want to take your boat to tahoe,its going to be fat because it was not programmed for the altitude.if it was carbed,all you would need to do is change some jets.i know smitty has this setup on his procharged engine,maybe he will chime in with what he had to do to make it work,and what it cost him.just think fella,s,a few more months and we can have this conversation out in the big lake over beers,or whatever it is you like to drink on a hot summer day.

100 % agree,,,,,Ill even take that a step further.

Merc sends them out to run anywhere in the world and on the worst fuel possible and be safe,,,,look at the first Gen 525 EFIs......soot the transom in seconds flat !!!

:evilb:And since you brought up cost to " make it work ",,,,,,now you know why I always leave my stuff the heck alone and just enjoy boating !!!!

Im to poor !!! LOL

I agree! And even worse, the stock 575SCI tune.

bob,i noticed you talking about your engine in a couple of threads,can you tell me about the parts list ?im interested to find out how to get that much power from a 540 that will idle low enough to put in front of a bravo drive.

540 dart block, 345dart pro 1 heads,comp solid roller cam, dart intake,1000holley carb, jesel rockers,elite comp lifters,msd box and dist.10qt oil pan.ss headers. i use a m1 a/f box to dail the motor in .

what is the cam part number,what pistons and can you post the dyno sheet.

NOT SHORE LORAZO BUILT MY MOTOR. 10 to 1 comp. 675 lift on the cam . dyno sheet i can not post picture here.http://www.youtube.com/watch?v=eL8i0Tnw7Qk 32degree timing . next run the timing was 34 . now i have it at 36 and i got a bigger carb 1050 dom

Type of dyno and more importantly, what is the correction factor set in the dyno that he uses?

Well my first experience was with a 600sc that even after having rebuilt both carbs and fu%#@king with both of them for hours on end ...on the water and on the hose, I could never get to idle decent or low enough.
Heres to my second carb boat experience being better.

:ernaehrung004:

Which is odd. The 600SC was supposed to be a very reliable and good running setup. Mercurys tune up spec called for 800RPM in gear idle speed. Same as the HP500 and other carb'ed high performance mercs.

This is where EFI has a advantage. You can have a 650RPM idle in neutral, and a 650RPM idle in gear. The IAC controls idle speed. Carbs, you just cant do it. The in gear idle will always be less than the in neutral idle. You just cant expect a big high performance carb'ed engine to idle at 600RPM.

A carb'd 1976 500CI Cadillac engine, sure. You can idle it down to 400RPM and it will still run. But a 190HP 500CI engine isn't gonna act the same as a 800HP 500CI engine. You cant expect it to.

I have a high performance boat. I grew up as a kid loving drag racing, loud engines, going fast and wrenching on my toys. I do it because I have a passion for it. If adjusting a carb screw, or idling 200rpm higher than my neighbors minivan bothers me, I need to get out of the hobby.My boat does transport my kids to school, I do not drive it cross country for business, it does not take me to the doctor for checkups. Its simply their to put a smile on my face when I lite the motors off, and go for a ride. If EFI makes you smile, by all means go for it.

I tune fuel injected motorcycles on my dyno on a daily basis and fully understand what it takes to tune one. That being said, I have a 750 rwhp twin turbo lightning (old 351 version) that I pulled the fuel injection off to try a blow thru carb setup. Reason is I get bored fast and I'm always doing something new with it and have grown sick of buying new injectors. I have at least 5 sets sitting in my shop. (19lbs, 24,30,42,72). Is that normal? Probably not. I know guys who built there hot rods 15 years ago and have done nothing, but change the oil since then. I can't do that. I am for ever changing stuff and just got sick of all the extra supporting equipment that changes on a fuel injected setup as you change or modify things. At least that's been my experience with my lighting that I've owned since 94' and had 3 different blowers, two different turbo setups I've built, two different nitrous setups, multiple head changes and who knows how many custom cams. I suppose I have a sickness and can't leave stuff alone. I'm not going to even mention bikes because its 5 times worse.

My current boat boat that I'm building I did pull the fuel injection off to build a carbed 509 for a couple reasons mentioned in this post. Since I can tune fuel injection I would want to try and tune the boat, but what I've read is that the mefi1 is not so great when it comes to tuning for many of the reasons listed in this thread. The thought of buying more fuel injection setups to replace the version I had wasn't even a thought. My last boat was a carb and in 150 hours (1.5 seasons) I never had a single issue related to the carb. If I have similar results with this new boat I will be more than happy.

On a personal level I think the mpi intake looks like poo and like the look of single plane intake and carb setup. That goes triple for a roots blower with carbs on top. I'm drawn to any and all roots blown cars at the shows like a bug to a bug zapper. Not sure why...probably the root to this sickness that I call my hobby.

I believe the new owner tried to adjust and gave up too, took it to a shop to have the carbs 'synced' and I think said it idles great now. I don`t know enough about carbs to like em, EFI is dummy proof, the PCM does all the work for you :stooges:

Lol at those smilies.

The majority of 25 OL are beginner performance boat buyers.

When I was buying my 25OL.. I was definitly looking for reliability and ease of operation. My last boat was a carbed 350 and ran well.. still had to pump throttle at cold start but wanted to turn key and voila!

its like selling your house with a pool. You limit your demographics and it will affect price.

if your selling... stay with EFI!

EFI is dummy proof, only on a stock motor if you add more hp to your motor you have to charge alot and you have to have a a/f box and computer hook to your motor to reprogram the computer. how many guys no how to do that??????? i like efi only when you have a stock motor. like me i am always making more hp on my motor .so carb is for me. i got a m1 a/f box and dail my motor in and gain 2mph because i was to rich, went down two size on the jets

I have to agree there bob!

Well I pulled the motor out tonight, going to remove the transom assembly tomorrow, going to do a leak down on the motor this weekend and decide where to go from there. Looks like one thing for sure I have a couple bad rust spots on my oil pan so I'm thinking that will have to be replaced. And while the motor and transom assembly are out I'm gonna throw a coat of paint in the engine compartment.

Bajabob and mild thunder, I like your way of thinking, if i chose to use the carb setup, i could get some better heads on there and decent cam and make some more power. Heck if the boat doesn't sell then at least the boat would be faster and I won't be chasing as many rooster tails this summer.

Seriously thanks everyone,
Maybe I should move that SEXY carb setup i have to a place where I won't see it everyday, and perhaps that will get this idea out of my head.
:lolhit:

At the end of the day, its your engine, your boat. Have fun and do what you wish with it. You never know, you just may want to keep it after a few changes.

I realize this is not my thread however I have been reading and I wondered if anyone has used the FAST ez efi kit to go from the carb to efi. It appears to be very easy but I wondered if anyone had any feedback...thanks

If you bought the stuff , put it on , if you dont like it take it off, you have the skill set to do it REMBER HAVE FUN

My mech. installed an outboard squeeze pump in line, give it a couple squeezes and fires right up !!

Well guy's...... Got some bad news! I know it's been a while since I posted on this tread but after my last post I did the leak down test and the results were not good! I had lots of blow by from the valves and rings. I brought the heads to the machine shop for a rebuild and got a call two days later......one of your heads is wasted and the other is not far behind. Ok so now I'm thinking I need to find a set of heads to put on then do a freshen up on the block, rings and bearings. I dropped the block with the rotating assembly still installed off at the machine shop. I got a call a few days later.....I think you better come down I got some bad news. Well come to find out the block is wasted to. They found a crack through the cap and block around the rear main seal.
This is not the news I wanted to hear a few weeks before the 2013 season kicks off. Its just weird that there was absolutely no signs of there being a problem with the motor last season. So now I'm in the market for a long block or a complete drop in motor.

Ahhh $HIT. How many hours were on this engine? very surprised to hear a stock 502 mag mpi that was running good to be junk and unrebuildable.

Well it wasn't exactly a stock motor. It was already punched to a 509, srp pistons, crane cam, comp push rods and lifters and crane gold rockers and an intake porting job from Arizona speed and marine. I bought the motor as a complete drop in at the begining of last season with 150 hrs on the rebuild and I put 40 on it so 190 hrs.....bummer!
The rotating assembly is still usable, there were some scuff marks on the crank were the bad cap was but the machinest said it didn't look horrible. He said it might not even have to be cut just a polish should take care of it. He also said you should look for a long block or a drop in motor and sell what good parts you have left.

that sucks . 190hours is nothing ! that motor should of ran longer then that.

Yupp that's what I would've thought. Any idea what would cause the block to crack in that location? I have heard people say that's where they are prone to cracking.......it doesn't seem like a common problem but I am just curious is that the weak point on a gm gen 6 502 block?

Any how i am going to look at a low hour hp500 long block this weekend. Hopefully we can make a deal and get this project wrapped up.