KeatonAZ

calling all the people who have done this...

I'm looking to switch to EFI and to do it on a budget. Usually those 2 don't go hand in hand but I'm going to try, I'm sick of dealing with this Quadrajet. My goal is to make the switch from carb to EFI for less than (or equal to) it takes to put a better carb on. Have better cold starting behavior, better doc behavior, and better throttle/TIP in response, any fuel econ, hp, speed pick up is a bonus. I want to be able to hit the key and have a consistent starting and behavior every time

my boat:
18Ft 1989 Seawirl Spyder 178 with a Chevy 350

I'm going to start with a chevy TBI system as it should be pretty easy to swap over. The distributor as the RPM pickup, the TPS,IAC, and injectors are located on the TBI unit. leaving the MAP sensor, o2 sensor, coolant temp sensor and a fuel pump.

according to the OMC service manual they ran the TBI setup for a few years so again in theory it should work, both should be L98 blocks

I spent a few hours in the junk yard looking for these parts. I was able to turn up a PCM (ECM +TCM) out of a 94 chevy truck (in theory it works)

PCM ~$30 (junk yard)
Distributor - $50 (rock auto)
Coil -$10 (rock auto)
TBI unit - Free!

Still need:
MAP sensor (rock auto)
coolant temp sensor (rock auto)
Wiring harness
fuel pump (15 PSI)
o2 solution
spread bore to TBI adapter. I know they make them but I'm gonna try to make one. I have some scrap aluminum, gonna trace the spread bore gasket on to it and the TBI gasket then cut, drill, tap as needed.
return line (tap into the breather)
surge tank (maybe)

USB to ALDL (data logging, ~$30)


if anyone has the stock 350 maps that would really help, if not I'm going to start with the truck maps and adjust from there.

dereknkathy

I have 2 big block TBI units.with the adaptors attached. I was going to do this to my hatteras a decade ago. bought a buncha parts and realized the boat is a summer house not a boat. you want to go open loop on the FI. although some people have put the oxy sensor on the exhaust heat riser in the intake manifold. Harristbichips on ebay used to be the guy for reprogramming that PCM. I have 2 or 3 PCM's around too. I tossed the car wire harnesses I collected. but they were too long and messy to use on a boat anyway. I found a thread where a guy did this convert on a 4.3. he was very happy with it. these big block units are old and dried out, but the 2 inch throttle bores will flow the air you need to run a 350 in a boat. probly cost 35 bucks to ship from NJ to AZ. hell, 60 bucks shipping included. I will make 25 or 30 on stuff the spousal unit is wanting me to go get scrap metal price for... that adapter sells for 30 to 50 on ebay by itself. found the conversion thread. he fabbed his own VST and made a cute little waterproof box for the PCM. http://home.hiwaay.net/~davida1/boat.htm

SB

I'll be second inline to KeatonAZ for the t-body units. Don't need the adaptors. Thanks !

dereknkathy

he probly is happy with the one he has. Sounds like you want both. What would they be going on? Need the PCM's too?

KeatonAZ

so the TBI bases 454 have 2x 2" throttle bodies, the 4.6/5.0/5.7 all came with a 2x 1-11/16". Not sure if I can run a 454 unit on a 350. My boat is a stock Chevy 350 so my guess is it needs ~500cfm. Also I have not picked up my TBI unit yet, doing that this afternoon. I told a few buddies what i wanted to do and one of them hit me up yesterday saying he his shop has one I can have.

I have seen that link before, I was also going to put the PCM in the box as they are not water proof or even water resistant.

for adding O2 sensors I have seen a few options:
1) Drilling and taping the exhaust manifold at 1 cylinder right as it enters the manifold. i need to check to see if i have the room on my stock OMC manifolds.

2) The Howell adapter General Motors :: GM TBI Products :: Parts & Accessories :: Miscellaneous Accessories :: #HM206 - ADAPTOR, O2 SENSOR for Marine use
3) A spacer (this will not work for me as I have limited Z height) but may work for others.


for the wiring harness I had been trying to find are car/truck on then was going to open it and strip out the stuff I stuff I don't need and put it back together. However every harness at the junk yard had been cut in some fashion.
I had looked at at painless harness but they want $500+ for their truck harness.
So I will build my own.
here are some of the connectors and ends
http://www.mouser.com/ProductDetail/...lZCOa3cZvqE%3d
http://www.mouser.com/ProductDetail/...Kcasx2ZZHzQ%3d
http://www.mouser.com/ProductDetail/...bkGFrG1l89I%3d
http://www.mouser.com/ProductDetail/...XPzOh97SvHc%3d
http://www.mouser.com/ProductDetail/...%2f4ZAe21VE%3d

I still need to find the OEM ends for the IAC, TPS, CTS, MAP, distributor. I did take some ends off the junk yard wiring harness, so I can always colder and heat shrink the wire if i absolutely have to. I don't want to created a failure point if I don't have to.

I'm also looking at CPC connectors (twist lock connectors OEM/millspec grade) to go form the water proof box to the wiring harness.

I also found out my PCM uses and additional box for the knock sensor, are people here running knock sensors? or do you run them rich with less timing to be safe?

dereknkathy

The car harnesses are also a million miles too long the way the wires seem to run a lap around the engine before they go thru firewall to hit the ecm. So they would Need to be cut and at least new connectors put at right length. And those new connectors don't have wires or probably even pins in them. So I think boneyard harness is best way to go. O2 sensor. The #1 cyl setup will only tell you what #1 cyl is doing. So if that plug fouls and that cyl misses, the ecm will lean out the whole engine. A lot of efi boats use no oxy sensor.

KeatonAZ

a lot of the boneyard harness I found were cut at the firewall, probably when they pulled the motor. instead of unplugging things they just cut it and moved on.

I'm aware that having only 1 o2 sensor on #1 will give me on 1 cylinder as a reading, but I'm kind of limited in options. 1 cylinder, nothing, or that brass adapter (prone to leaking?)

SB

A few trucks. No PCM's needed.

KeatonAZ, do you want derekncathy's tbodies ?

KeatonAZ

I don't think those will work for me, too big

CFM = CID x Max RPMs / 3456 x Volmetric Efficency.
So: 350 x 5000 / 3456 x .80 = 405.09 CFM carb size. (80% is very optimistic for a stock marine 350)
stock 350TBI is rated for 550CFM


if I use some rough numbers TB size = sqrt ((11978.8*Liters*max rpm/67547))
So: TB size = sqrt ((11978.8*5.7*5000/67547)) = 71.0929mm
1-11/16" = 1.6875" = 42.8625mm (each) *2 = 85.725mm

unless I'm doing something wrong...