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View Full Version : Converting to EFI, LT1 anyone?



Ryan23
07-16-2006, 07:47 PM
Excuse the ignorance on a few things, I'm a car guy and I'm trying to make some sense of what goes on in the marine world....

Would there be any drawbacks to converting from a carb setup to EFI using an auto-sourced intake, harness & ECU? I was specifically looking at using a Gen III LT1 setup from the early 90's Vette/Caprice/Camaro/ETC. These setups are relatively cheap & plentiful nowadays and seem like they could offer a nice bump in hp as well as reliability.

The main issues I see are:

HP Fuel - Intank pump and new fuel lines would need to be ran.

Heads - Pretty sure the inner manifold bolts are angled in a bit more than the outer ones, as compared to traditional SBC heads. I know that's the case with TPI (86-92) Chevy heads. Either way, better flowing iron & aluminum heads are available for LT1 (and cheap too).

Wiring and finding a dry spot for the ECU.

Converting over to an Optispark setup for the ECU.

Converting from MAF to speed density.

Figuring out what to do with the O2 sensors (either deleting them and running a well tuned map or integrating them with existing headers).

Am I missing something here? There are a few other necessary sensors but they are pretty minor in the grand scheme of things. Just looking for a relatively cheap and reliable way to get a pair of low hour 4 bolt main marine blocks (probably 260hp variants) up to ~400hp each. Cam/heads/EFI would be a walk in the park to reach that goal, in my experience. Has anyone done something similar?

Thanks,

Ryan

zimm17
07-17-2006, 05:54 AM
No personal experience, but I don't think it's a good idea to use a non-marine system in a boat.

For the max bang for the buck- I'd go with a performer rpm intake and marine carb. Boats are easier to tune with carbs than cars- throttle response isn't nearly as important.

If you are stuck on EFI, look for a used takeoff from a EFI 5.7L merc. A lot of people remove all that stuff for a carb to make more power.

gcarter
07-17-2006, 06:13 AM
Didn't GEOO go with an aftermarket EFI system on Mighty Mouse?

LKSD
07-17-2006, 07:12 AM
It is a lot of work to do the system you want to use & is not advisable. It would be better to get a merc take off system from ebay or buy a new F.A.S.T. system to work & custom install on a marine application.. It isnt cheap though, but it is better power & reliability...

Jamie / Lakeside

Ryan23
07-17-2006, 11:40 AM
It is a lot of work to do the system you want to use & is not advisable. It would be better to get a merc take off system from ebay or buy a new F.A.S.T. system to work & custom install on a marine application.. It isnt cheap though, but it is better power & reliability...
Jamie / Lakeside
Jamie -
I appreciate the reply but I was hoping for a little more concrete of an answer as to why not. There are a couple options for the LT1 top end:

- www.lt1intake.com can mod an LT1 intake to bolt up to traditional SBC heads with the hole for a distributor ($200 per intake). The intakes themselves can be purchased complete (with fuel rail/injectors) for under $100.

- LT1 heads could be used but the forward water passages would have to be welded up (then milled) for use on a traditional SBC block. The LT1 heads do flow a bit better and a pair of ported ones (LE1) could be had for ~$1200 with a matching (mild) cam.

I have some experience with the FAST setup and it's a little pricey/overkill for what I would be trying to do. LT1edit could be used to tailor the stock PCM for marine use.

With a properly selected cam and a set of mildly ported heads, a pretty broad torque curve could be realized. Take this example below, peak power was 403hp @ 6500. At 5600, power was still 398 hp. Remember, these are rear wheel numbers, so actual power would be (ballpark) around 15% higher. It's my understanding that bottom end & midrange power needs to be emphasized for a boat. ~5500 RPM max, no?
http://memimage.cardomain.net/member_images/1/web/769000-769999/769972_98_full.jpg



Just looking for a little clarification, is all. There were a few folks who scoffed at me for removing the twin turbo rotary engine from my Mazda RX-7. I replaced it with a 450 Rwhp Chevy LS1 (V8) and ended up with a lighter and MUCH faster car. I'm not new to turning a wrench. :)


Thanks,
Ryan

HallJ
07-17-2006, 11:57 AM
Ryan,

Having actually done a swap like this. I can say it is relativly easy and works quite well.

I used a 91' vintage gm speed density system with the corvette underhood computer which is better for a marine environment.
The closed loop o2 control is nice.
Are you planing in using an LT1 or just the managment system from one?

Jeff

Ryan23
07-17-2006, 12:12 PM
Ryan,
Having actually done a swap like this. I can say it is relativly easy and works quite well.
I used a 91' vintage gm speed density system with the corvette underhood computer which is better for a marine environment.
The closed loop o2 control is nice.
Are you planing in using an LT1 or just the managment system from one?
Jeff

Hey Jeff -
Thanks for the reply. That's the kind of info I was looking for. I'm leaning towards using the LT1 topend, just the heads,intake, cam & management (with the heads modded as I descibed above). The motors in the boat are pre-86' four bolt marine blocks (Gen 1) which purportedly only have ~70 hours on them. Seems like it would be a waste to yank them. I'm guessing you used the full up Gen II block? Did you come across any issues during installation? If you came from a carb setup, how's it compare?

thanks,

Ryan

Brian Hamilton
07-17-2006, 04:46 PM
Ryan, Before I bought my 22zx I had a 94 mastercraft With an Lt-1. It was an indmar motor, and was set up for marine use. It was rated at 310 hp. (propshaft). That boat would come out of the hole like a rocket. You may be able to get All sorts of parts for an Lt-1 from mastercraft or indmar. They spent a fortune on this motor to get it set up for marine use. You should have seen the looks I got when I lifted the engine cover and people saw the Corvette fuel rail covers. nice. Brian

LKSD
07-17-2006, 05:50 PM
Ryan,
You can do it the way you are thinking & it should work fine. I just have seen complete merc take off units on ebay at times for 1k with the ecm.. Just bolt on & go. I thought this may be faster & easier for you. Actually it still may be by the time you are done.. I do agree with you as far as the FAST system being expensive & overkill, I just thought I'd throw annother idea out there.. Also one of the other reasons for my like of the merc marine efi system if you could find a take off was ease of parts. ALthough the prices for your LT1 link you had up earlier seem to be pretty inexpensive as far as that stuff goes... I wasnt trying to bash your idea, I just wanted to help with some other thoughts.. Sorry if I was or are to vague... Let us know how you make out.. Thanks Jamie :)

Ryan23
07-17-2006, 06:22 PM
Ryan,
You can do it the way you are thinking & it should work fine. I just have seen complete merc take off units on ebay at times for 1k with the ecm.. Just bolt on & go. I thought this may be faster & easier for you. Actually it still may be by the time you are done.. I do agree with you as far as the FAST system being expensive & overkill, I just thought I'd throw annother idea out there.. Also one of the other reasons for my like of the merc marine efi system if you could find a take off was ease of parts. ALthough the prices for your LT1 link you had up earlier seem to be pretty inexpensive as far as that stuff goes... I wasnt trying to bash your idea, I just wanted to help with some other thoughts.. Sorry if I was or are to vague... Let us know how you make out.. Thanks Jamie :)

No sweat Jamie, I didn't think you were bashing it :). We talked on the phone last week about my prospective purchase. You should be seeing my "new-to-me" boat in a couple weeks. If all goes well, I'll be picking it up this Saturday :hyper: . (and yes, it's not even here yet and I'm looking at ways to make it faster....lol...such is the disease)

Ryan in Maryland

onesubdrvr
07-17-2006, 06:45 PM
Regarding the ECU on the Mercruiser system, can't it be reprogrammed for optimum performance (ie with the addition of a supercharger, or head work / bore / stroking an engine)? Where does this kind of work get done?

Thanks
Wayne

LKSD
07-17-2006, 07:12 PM
Ryan, No Problem good luck on the boat & hopefully we will see you soon.. :) Jamie


Wayne, yes most ecms can be reflashed. I have done some, also some other dealers & facilities can do ecm reflashing of the merc modules as well as other moddules. Certain ones we sub out for certain situations & applications. The modules do not always need recals thought even when supercharging. It depends on what you modify & how much you modify it... Jamie :)

HallJ
07-17-2006, 07:42 PM
Ryan,

If you can get the intake manfold to work, you will have to plumb a remote thermostat housing.
If your not Using an LT1 motor you will have difficulty integrating LT1 managment. Depending on the year of LT1 you will need to integrate The Opti spark trigger, and the Crank trigger. it would be easier to use an early 90's style Speed density system from a TPI Corvette/Camaro as I have done. I sourced my wiring harness, Ecu and custom Prom From TPI Specialties. Truly plug and play.
One thing I like about the GM system over a marine one is the Closed loop O2 control at idle and part throttle.
Jeff

gold-n-rod
07-17-2006, 08:12 PM
If you are going to take the plunge, get rid of the optispark. They hate moisture and would fare poorly in a marine environment.

I like the idea of sourcing lt1 marine parts. I think (but I'm not sure) that it was Pleasurecraft that marinized the lt1.

Sure sounds like a lot of work, though.

:wavey:

Ryan23
07-17-2006, 08:27 PM
Ryan,
If you can get the intake manfold to work, you will have to plumb a remote thermostat housing.
If your not Using an LT1 motor you will have difficulty integrating LT1 managment. Depending on the year of LT1 you will need to integrate The Opti spark trigger, and the Crank trigger. it would be easier to use an early 90's style Speed density system from a TPI Corvette/Camaro as I have done. I sourced my wiring harness, Ecu and custom Prom From TPI Specialties. Truly plug and play.
One thing I like about the GM system over a marine one is the Closed loop O2 control at idle and part throttle.
Jeff

That's a good point on the LT1's management. The Optispark units don't exactly have a stunning track record either. Talking with Lloyd Elliott today (LT1 head guru), I would probably be better served running a set of off-the-shelf sbc heads, IE: 200-215cc Dart I's or the like. Flow-wise, they're pretty comparable to his ported LT1's and are standard cooling. I could have the LT1intake guy just mod the intakes for standard SBC heads. Full up Dart Pro 1's run anywhere from $800-$950 a pair.

One thing I was trying to avoid was memcal's. Are all the TPI setups memcal or did they switch over to Eprom's in 91 or 92? Burning chips can be a PITA, maybe I ought to put a little more thought to going standalone. Decision...decisions...

Incidentally, PHR ran an article awhile back for anyone else looking into this. It was on a 3rd Gen Camaro:

http://popularhotrodding.com/tech/0803phr_tpi_intake_conversion_ls1/

Ryan

LKSD
07-17-2006, 08:42 PM
When did Merc go open system on the PCM's??

Mercs systems are not really open. You need special software to crack into them. Unless you have it or someone from mercs facility like a rep does an alteration it is not something that can easily be done. Usually we sub out the merc stuff. Some of the other brands we can get into & download recals into like Indmar for example. Merc & volvo are tough on letting you into their ecms... J :)

HallJ
07-17-2006, 09:35 PM
Ryan,
All TPI's have proms. the memcal is the part you pop into the ecm.
It has the prom and ESC chip on it. there is software available to program these things real time using an EPROM emulator. When you get it dialed in, you burn the final program to the EPROM.

Depending on what outdrive you have you will have to be carefull how fast you spin the motor. You will also have to take it easy on you cam selection compared to a car setup.

I'm using an 88' vintage block with Vortec heads and a merc 320 EFI intake manifold.

Ryan23
07-17-2006, 10:17 PM
Ryan,
All TPI's have proms. the memcal is the part you pop into the ecm.
It has the prom and ESC chip on it. there is software available to program these things real time using an EPROM emulator. When you get it dialed in, you burn the final program to the EPROM.
Depending on what outdrive you have you will have to be carefull how fast you spin the motor. You will also have to take it easy on you cam selection compared to a car setup.
I'm using an 88' vintage block with Vortec heads and a merc 320 EFI intake manifold.

Thanks again, I didn't realize that Eprom emulators existed. That's not a bad option either. It's been about 10 years since I touched anything labeled "Tuned Port", so my knowledge is a bit dated. Now you want to talk LS1's, we could chat all day :)

Ryan