Converting our boat to fuel injection

So my friend and I are converting his 94 Malibu Echelon to TBI fuel injection. Our carburetor has been giving us nothing but problems this last year, and instead of replacing it or rebuilding it again, we are upgrading. I did a compression check on the engine and every cylinder was at 178, so we defiantly have a good engine! Its a Mercruiser Comp Ski Magnum 5.7. I got the TBI unit and distributor from a 92 Chevy 1500 truck that had a 5.7 TBI engine in it. I ordered a computer, custom harness, marine fuel pump, map sensor and adapter plate from Affordable Fuel Injection to run the whole system. The guys at Affordable Fuel Injection are awesome! We are running an open system w/o the o2 sensor. The only bummer thing is we got shipped the wrong adapter plate, but it will be here on Monday, so once that shows up we will be good to go! Here are some photos of the project so far. I already put the new distributor in the boat, but you can see the whole kit we got. I removed the old fuel pump and blocked it off with a block off plate from Napa. All the original fuel hoses to the pump and carb were removed too. We have to make a box to protect the computer because its just like one out of a car. We are making a water tight plastic box for it to put it under the dash. The guys at A.F.I. make the everything to your specs, so our computer is programed for a 160 thermostat, the specific type of distributor and TBI unit we have and also only running the sensors on the TBI and the map sensor. The kit comes with detailed instructions on how to install it too. A.F.I sells the distributor and TBI unit, but it was way cheaper to get one from a donor vehicle. Super easy setup. I had marine fuel hoses made and the fittings clocked so we never have to worry about a hose coming off or sucking air. Everything screws together. Here are some photos...

Hi Kyle,

If you dont mind me asking, what did this project cost so far? My I/O is carburated and i would be interested in switching to EFI if it's not too expensive.

so far I paid $50 for the TBI, $50 for the distributor, $120 for fuel hose and pressed fittings (marine fuel hose is expensive), $900 for the injection kit which is the wire harness, adapter plate, map sensor, fuel pump, temp sender and computer. $30 for the new cap and rotor on the distributor. This is the cheapest way to do this kit. I probably could of shopped around and saved a few bucks on the fuel pump, but I just wanted to get it all at once. I paid $1150

If you bought the complete kit from Affordable Fuel Injection or Holley, you are looking at $1500 for just the kit (harness, tach filter, computer, fuel pump, TBI and sensors.) You would get a tach filter instead of a distributor made for fuel injection. The tach filter is nice because you don't have to change your distributor, but you don't get as good of performance from it, and its $75 for the filter. I paid $50 for my distributor at a used auto parts place. Then after you buy the kit you still have to buy fuel hose too. If you know what your doing, I would piece it together. Save a couple hundred bucks. Even if you have to rebuild the TBI, the main thing that goes wrong on them is the pressure regulator, and the whole rebuild kit w/o new injectors is like $30

Wow that's pricey and it is still going to be a type of TBI so the HP gains will be very minimal. I can rebuild my Holley about 20 times on that budget and expect great performance.

Looks fun. Post up progress.

The stock carb on this boat was a carter 4 barrel 600cfm stove choke carb. Honestly...they suck! Its been rebuilt before about 2 years ago, but its acting up and using excessive amounts of gas. We should see a huge difference in power and fuel useage. The other bad thing about the carburetor we had was when you surf for a regular rider, its ok, but when you surf a goofy rider, the boat runs horrible and rough. It didn't want to idle. Having a electric fuel pump and a computer monitoring the fuel system will resolve this problem big time! We well gain HP just because of how efficient TBI works compared to a carburetor, but mainly we are looking forward to turn key start, smoother running and less fuel being burned. Because the fuel is pressurized and injected, you use less fuel for the same amount of power verses a carburetor. A carb uses more because its all done mechanically. The little passages in the idle circuits can clog, floats can stick, elevation change can mess with them, and that's a common problem living in the North West if you travel to different places. I agree a Holley runs awesome and much better then a carter or edelbrock carb, but a Holley would cost almost $700 to buy new. We just decided to spend a little more and have a way better system then a carburetor. We use this boat a lot, so its going to be nice to have a much better running engine!

Its an expensive investment, but I bet it will pay for its self because our fuel consumption will come way down. I can't wait for Monday to fire it off!

I bought the AFI (Affordable Fuel Injection) MPFI system last year for my project Suburban with a 427 Big Block. The guys back there where awesome and the sytem rips! The best is I just lean in the window and tap the key and my 427 starts! It used to take a minute to start! Great company, there quick and responsive with every question I ever had!

Yeah AFI is awesome! was your suburban running off a carb before you did the swap? Was there a noticeable big difference in power?

I might have went the MEFI route instead. MEFI 3's and 4's are becomming more available. You may have been able to source a manifold and throttle body from a hot boater that upgraded his stock merc units.

I was running an edelbrock performer on the 427 before the swap. I couldn't tell you how big of a differance the Fuel Injection made as I had the motor built up when I did the swap so its a full roller putting out about 550hp now. I can tell you the cold start issues are gone, as are the hot start issuses and the throttle response is as quick as my corvette. After years of playing with carbs I'll never touch another carb the system was easier to install the putting a new carb on after you realize you don't have to tune the system. Everything was plug and play and just bolted on with the exception of the O2 sensor which i had to weld into the headers. Would do it again in a heart beat. You could buy everything you need to make the same system for about $1500 but haveing everything done and color coded and machined was worth every penny! I think the system ran me about 2500 to the door and included a new computer controlled ditrubutor too!

I just rebuilt the TBI unit this evening. It was really easy to do. Tomorrow I'm installing the new fuel lines, fuel pump, the wire harness, and mounting the computer box in the boat. I'm getting everything all finished up because the correct adapter plate shows up on Monday! I can't wait to fire the boat off and ride!

cant wait to see the results!

Ok...So I finally have it pretty much all together. Yesterday I installed the new electric fuel pump, all the fuel lines, the TBI adapter plate, the newly rebuilt TBI unit, I made a bracket for the Map sensor and replaced my Thermostat. I had to check to make sure it was a 160 and not a 140. It ended up being a 160...I had to remove all the gaskets and replace them for nothing... eh. I Installed the new temp sender for the computer, and hooked up all the sensors to the computer harness. I had to make a T fitting for the fuel return, so tonight I'm going to finish it all up installing the wiring for the computer, mount the computer and it will be all done.

Only problem we encountered was the linkage bracket that holds the throttle cable didn't line up because the TBI unit is farther back then the carb was. we are welding a bracket to take care of that. I hope we can start it up tonight! its been raining like crazy here the past few days...

Here are some photos of the progress.

Nice write up

I didn't have a chance to start it tonight. It started to rain. My friend welded the screw for the spark arrestor so that it all lined up in the center, because the screw hole for the TBI unit it not in the center. I installed my T fitting for the fuel over flow. Its set up so the fuel shoots straight into the tank and the fuel tank overflow goes out the top of the fitting. I decided to put the computer in the back of the boat on top of the gas tank so it stays dry and is away from heat. Its in a plastic box so it will be protected. I figured the back would be best so the computer won't bounce around as much as it would in the front of the boat. Its not something I will really ever need to access often, so I think its a good spot for it. I finished up installing the extra wires and the service engine light for the computer. The new bracket for the throttle cable worked out perfect! I pulled it off and painted it so it should be all dry tomorrow so I can install it. I hope I get a break in the weather so I can start the boat!

Here are some more pictures of the work I did tonight...

u know holley makes a complete Fi conversion kit for about the same price.. i might have me a project for next winter =) http://www.summitracing.com/parts/HLY-700-21/ btw, for what is the tee on the fuel line for?

i guess that tee is for the fuel return?

The T fitting is for the fuel return from the TBI. The TBI on the back has two inputs for fuel, the send and the return. The TBI unit has its own pressure regulator so it sends the unused fuel at a very low pressure down the return line. the T fitting is for that. Its hooked up to to the fuel overflow on the tank. Every fuel injection returns the fuel back to the tank except for the stock Mercruiser systems.

The Holley system is cool, but one bad thing about the holley system is that it doesn't come with a distributor, it comes with a tach filter. You should check on that before you buy it. Having the newer style distributor like what I installed (same distributor out of a early 90's chevy truck 5.7) is a good idea because you get a better timing advance setup. I would look into that before you buy it. You can get the complete system from AFI made just how you want it, and it comes with everything you need minus the fuel hoses. I would probably do the AFI way again if i did it over, and get the distributor and TBI unit from a donor chevy 5.7. Rebuilding a TBI unit is SUPER EASY! It took me about 30min to do. Theres not much to them. Another nice thing about having a TBI straight from a Chevy truck is that if you have a sensor go out, getting a new throttle position sensor from any auto parts store is really easy to find. I would go with the AFI system again

does the AFI TBI setup use a map sensor or anything to meter the airflow? I looked at the Holley system and it seems it just uses a throttle position sensor and coolant temp sensor and thats it.

Yeah the AFI system uses a map sensor. I think all TBI systems need to use a MAP sensor because it senses the atmospheric pressure in the engine. You can also use a O2 sensor to make it a closed system, but I decided to go without it and make it an open system. Overall, I think the AFI system is a better system if you buy the TBI and distributor your self. I just told them what I had and how long the wire harness needed to be. The kit from AFI came with a adapter plate for the TBI, wire harness, marine fuel pump and filter, map sensor, temp sensor, check engine light, computer, and instructions for installation. the kit was $920 with shipping. The TBI and Distributor were $100 for the both from a used auto parts store. The hoses cost a little over $100, but my boat is a direct drive so the return line was a little over 10ft. The rebuild kit for the TBI was $30 and i also bought a TPS for the TBI which was $20. I probably spent about $30 at the hardware store for random stuff like to make my T fitting and bolts for random stuff and hose clamps. I'm at about $1210 for everything. Even with the Holley system you are going to need to get fuel lines and other random parts for your system. I think the AFI system is cheaper overall, and like I said, if my map sensor or any other sensor goes out on my system, I can get replacement parts at any auto parts store. The Holley ones may be harder to find.

There are tons of TBI units and distributors out there due to the cash for clunkers thats been going in. I went to a chevy only wrecking yard and had lots to choose from. There is really nothing to rebuilding a TBI either. its a couple of gaskets, a few O-rings and 2 little filter screens on the injectors. only tools you need is a standard allen wrench set, a scraper for the gaskets, a can of carb cleaner, and some standard wrenches. It only took me maybe 30min to do, and I had never done one before.

How are of the distributors different between carb/FI setups? Is it just the timing curve? I think my carb actually has a TPS sensor on it but I gotta check it to be sure.

There is a big difference from the carb distributors and ones designed for TBI systems. The ones made for TBI systems are much more high tech. The computer controls the timing. In order to set the timing on a TBI there is a special wire that you ground out to the engine. This stops your advance so you can set the timing where its suppose to be. Once the ground is removed from the distributor, if you shine a light on the timing mark you will see the mark bounce around. This is because the computer is controlling the advance so its running optimal performance as possible. You don't have to change the distributor, you can just use the tach filter, but it wont run as good as the distributor designed with the TBI systems. You can buy a new re-manufactured one for about $100 on line. The guys at AFI recommended that you should go with the TBI distributor.

The boat is finally ready to start! Its rained all freakin day though, so I didn't get to pull the boat out of the garage. We ran into a little problem with the linkage on the TBI unit. Where the throttle cable hooked to the TBI, it took away some of the throw on the Throttle. We had to make a special plate to lengthen the throw of the throttle. Everything turned on when i turned the key to on. The fuel pump primed...it was nice to see all the hard work I as well as my friend have put into this project come to life. The computer box was finished and mounted on top of the gas tank. Here are the photos of everything. I hope I get some good weather tomorrow!!!

The computer box is held down by a strap, but there also is a bunch of silicone holding it to the tank so it won't move.

Looks great. Glad to see it's working out. Only possible problem I see is the 1-bolt attachment for the throttle cable mount. That will probably loosen up fairly quickly during use.

Holley's Pro-Jection system is a joke. You're on the right track with this setup.

Which part of the throttle cable mount are you talking about? The bracket holding the cable support it bolted down in two places, on the adapter plate and where the coil mounts to the intake manifold. Its actually 2 pieces of metal, the arm off the TBI plate, and the support that bolts to the coil bracket. The cable support is bolted down through both pieces and is held with a nyloc nut. Its really strong and cannot move at all. The adapter on the TBI unit throttle linkage to give us more throw is held on by 2 bolts and bolted on with nyloc nuts. Its pretty solid, I don't think there will be any problems.

I agree, the Holley system is good, but I think you can build a better system from AFI for cheaper then Holley's system, and with a Rochester TBI unit, all replacement parts are available at any auto store. I bet the Holley ones are a little harder to find, or they will have to be ordered.

im looking forward to seeing this thing run.. hopefully you can make us a video!

My bad, the throttle mount looked to me like just one bar to the adapter plate. I see the lower bent bar now. I changed my mind - it's perfect!

Haha! Thanks! Well I finally got to start the boat!!! It ran amazing! Barely turned over and it fired right off! Due to the horrible weather we are having here in the north west, I didn't get to take it out on the water, but hopefully tomorrow will be a little better so I can take it out for a test drive! Fuel injection rocks! I will let you all know how it turns out after the test drive!

Going for the official test drive in an hour! Stoked!

HOLY CRAP!!! I just got back from finally driving the boat! It feels like I put a whole new engine in it! The throttle response is amazing, it holds speed so well! Super solid! My hole shot is way faster too. It rockets up on plane! I'm getting more RPMs out of the engine too. I can almost get 5000 rpm. I know its bad to go past 4500 rpm, but I have a feeling when we put all the 2500lbs of ballast in the boat plus the people, we will be getting up on plane faster! I can't wait to see how much less fuel its going to use too. This project was an awesome investment! If you are mechanically inclined, and understand how fuel injection systems work, I highly recommend doing this to any boat that has a carburetor on it. Its totally worth the money!

thats awesome news! what prop are you running? I got a another question about the distributor: it looks like you have the original coil and distributor cap on your engine, I thought the chevy truck distributor has the coil that sits on top of the cap?

I'm using the the original coil from the boat. The plug on the back of the distributor with the 2 wires on it hooks to my coil. It does the same thing. I can buy a hotter coil if i need to, but it seems to be working fine. The guys at AFI told me it would work fine.

I'm running the ACME 525 3 blade prop. It was the best one for slamming a boat for wakeboarding about 4 years ago. its a 11.5 x 13 prop with oversized blades. I don't remember the cup.

I'm stoked! We are going wakeboarding tonight! Get to give the engine the real test!

Been watching this for a while. Congratulations dude. Be sure to wear your mask & cape on the first run! hahaha!

The boat ran great! It was nice to finally get to ride! I'm going to advance the timing a little bit to get a little more power out of it. Could not be happier about having fuel injection!

this was a cool project, i think i might do the same thing next year

Yeah it was totally worth it! The only thing I need to do is figure out how i can take some of the tension out of the return spring on the TBI. The throttle is a little stiffer then it used to be.

Originally Posted by RidingTheNW

I'm using the the original coil from the boat. The plug on the back of the distributor with the 2 wires on it hooks to my coil. It does the same thing. I can buy a hotter coil if i need to, but it seems to be working fine. The guys at AFI told me it would work fine.

I'm running the ACME 525 3 blade prop. It was the best one for slamming a boat for wakeboarding about 4 years ago. its a 11.5 x 13 prop with oversized blades. I don't remember the cup.

I'm stoked! We are going wakeboarding tonight! Get to give the engine the real test!

I used to run that very same prop in my Calabria Cal-Air (DD), made a HUGE difference. Funny, I did not realize how much better that prop was till I dinged it up on Lk Sammamish one day, put the stock OJ back on while the Acme was repaired. Boat felt so slow with the stock 4 blade prop (think it was 13x13)

I think you can pull the tps sensor off. Remove the blades from the shaft. There may be a compression washer behind the tps sensor. If so tap the shaft with a hammer and it will slowly come out. At that point you might be able to uncoil the spring one time so that it does not have as much tension on it. On some TB's and TBI's the blades and shafts are not removable. I'm sure you know this though.

We did some wakeboarding last night. We advanced the timing to 4deg BTDC. The engine feels really powerful now! I noticed that we have more torque. The hole shot is better and we are using less engine power. The RPMs are lower at the wake speeds we ride (about 24mph) We had about 2400lbs of ballast and the 3 of us in the boat. The coolest thing that I noticed was doing turn arounds or double ups, the engine holds the speed much better and I have to use less throttle in the turn versus when we had a carburetor. This is probably because we no longer have floats controlling the fuel flow. The boat had more power and torque through the turns. We did a surf test too. When the boat had the carburetor, it would surf fine for a regular rider, but for goofy surfers it ran like crap and it would use more gas. Now it runs the same on each side and uses less RPMs to get the perfect surf wake. it used to use almost 3000 RPMs for surfing, and now its using 2600 RPMs. Our fuel consumption is lower and the engine just feels stronger.

I highly recommend this project! If anyone decides to do this to their boat, feel free to ask me any questions about it.

Here is some photos of the boat. Its a 1994 Malibu Echelon. We have a plumbed in auto bow ballast system that holds 500 lbs that fills/empty's at the flip of a switch. 300lbs of lead under the back seat, 540lb sacs on both sides of the motor box, and we put a 280lb fat sac on the back seat and a old leaky 540lb sac filled half way between the motor box and the back seat. The boat has the SV23 hull so its the same shape as the original wakesetter. Wedge (which we only use for beginners and for surfing) Samson tower, Fusion T combo series tower speakers. 12in kicker sub in a fiberglassed ported box under the bow. 1400 watt 4 channel boss amp running the tower speakers and interior speakers and a 500 watt JL audio mono amp running the sub.

^super cool!

Hello Kyle Riding The NW. One ? 2010 you did a tbi conversion on your Malibu. Have you had any problems with this new system sense installing it? You seemed well pleased with it at the time. I'm not into wake boarding but love my fishing and I do have a older boat with a carb that I want to change out. Enjoyed your forum on this project. Ron