351 Windsor carb to EFI done

Hi All,
I came across this site by chance and noticed a thread about converting the 351 Windsor from carb to EFI. I have done this on my engines and would be glad to share what I've learned with anyone who is interested in this sort of thing and hopefully gain some knowledge from others who have may have done the conversion as well.

I am one of the folks considering the EFI swap, but I usually get scoffed at because of the time and money involvement :-)

I just picked up a complete EFI system off a OMC 5.0 Cobra that was on ebay, but I haven't picked it up yet to look over the parts. I know the manifolds won't work, but am wondering how much else I'll need to replace.

Tell me what you did. And pics would be great too

Don

Bob,

Even though we're talking about a Bayliner, welcome. You may get a little heat about it but any informative info to this group of boating gearheads is worth the price of any friendly ribbing. Thick skin is also a benfit. I myself don't own a CC but I've been welcomed by all here (or most anyway) none-the-less.

There are several of us who "knows someone" that has tried this conversion. In virtually every case, the hours, money and frustration led to a very expensive EFI kit collecting dust on a shelf and a carburetor sitting where it was originally intended. This usually after an entire season.....or two....or more of watching others burning up a lot of gas in their carbed ski machines while trying to get that magical Holy Grail of modern induction to run. Sometimes just being able to get the friggin' thing started would be an accomplishment let alone getting it dialed in.

The general concensus here is if you want EFI, buy a boat that came with it from the factory. I do know that any information in your EFI conversion would be of special interest to many here so feel free to post away and before anyone else says it, pics are always greatly appreciated.

Also be prepared for a lot of questions. There are a lot of very sharp dudes here when it comes to what makes a ski boat go....in several cases what makes a ski boat go very fast. The fact that you've done this with a 351 is even more intreging (sp?) so the floor is yours as they say. Enlighten us.

I'm intrested in learning, but don't really see a need for it at this point, you have pretty much summed up how my engine spends the majority of its time. I don't know that we have had anyone here try to use something that is not plug and play (supposedly).   If you have successfully made the conversion I guessing you have some experience with tuning these before you started this. That seems to be the common problem here, plug and play doesn't work or works sporadically and nobody has the experience to adjust it manually to solve the issues.

KR,
My, where to start? Some back ground might help.

I'm 66 years old, an electrician by trade. I should be retired but I have too many expensive habits, the worst of which has a pair of 351 Windsors in the engine room. I've been twisting wrenches as a serious hobby since I was old enough to pick one up.

About 12 years ago or so we bought a motorhome. '92 Winnebago Elante 33 on a Ford chassis, fuel injected 460 with an E4OD automatic transmission. The stock shift and torque converter clutch scheduling on the transmission drove me to distraction so I set about looking for an aftermarket stand alone programmable transmission controller. Having no success I began toying with the idea of building one. I have no formal training in electronics of computer programming but I had met a young fellow who was an electronics tech and programmer. I bought the factory E4OD manuals so I could fully understand how the thing worked and we built the “Mark I” model using a Basic Stamp chip and some peripherals to handle the math. It was slow, but it worked quite well. One thing lead to another and I found that I wanted control of the engine as well, partly because I figured out how to use an exhaust brake on it. I bought a Haltech E6K engine management system and used that for a couple of years. It was OK but I still wanted more custom control and the hardware and firmware on the Haltech is proprietary.

Enter “Megasquirt”. At the time Megasquirt was fuel only, but it was a build it yourself kit and the firm ware was open source, which meant it could be customized. It uses a Motorola HC908GP32 processor and is programmed in Motorola assembly language. I bought some Motorola books and proceeded to teach myself how to program in assembler. In the mean time a fellow by the name of Magnus Bjelke developed the “Megasquirtnspark” code for ignition control as well as fuel. I took his code and modified it to work with the Ford TFI ignition. Now, all this can be pretty scary stuff, because when dealing with control at this level you certainly have enough rope to hang yourself, and I really didn’t want to destroy the engine or transmission in the motorhome. So happens my daily driver service van is a ’95 Ford E-150, 300 inch I six with an E4OD. I decided that it would be my test bed for all the changes, so I used my Mark I transmission controller and Megasquirt to gain experience. After a while I figured I could improve on the transmission controller so I built the “Mark II’ version with the design based on what I’d learned with Megasquirt. To date they have been running the van for over 8 years and over 100,000 KM with not a single controller related break down.

But what has all this got to do with the 351 marine engines you might ask?

About 8 years ago we bought our boat. For those of you not familiar with the 3288 Bayliner, they are 32’ from transom to bow, 29’ at the waterline, 11’6” beam and weighed about 15,000 lbs when they left the factory. They have a semi-displacement hull, which means that they will plane, given enough power, but not nearly as efficiently as a true planning hull. Basically it’s more power, more speed, more fuel. There is no well defined “sweet spot” as on a smaller true planning hull boat where you can get up on plane and actually throttle back a bit to maintain the same speed. Like her owner, “Hocus Pocus” has gained some weight over the years. She now tips the scales at around 17,000 lbs. As best as I can determine her true planning speed is about 17 knots. She would do an honest 27 knots at WOT when she was light, but now, with the added weight, about 23 is tops. The fuel burn at this speed would bring a smile to the face of any fuel dock owner.

The most economical speed for any boat is about 2/3ds of hull speed. Hull speed on our boat is about 7.2 knots. That works out to about 5 knots. It takes a long time to get anywhere at 5 knots. We’ve found that over the years we prefer to cruise at about 8 knots, 1800 RPM, 56 KPA manifold pressure absolute. There is no need to use the trim tabs at this speed so there is no drag created from them. Above 8 knots full down tabs are required. If we are in a hurry we’ll bump her up to 2800, 78 KPA manifold pressure which is about 13 kts. If we are really in a hurry 3200 and 84 KPA will get us about 17 knots. Anything more than that I consider emergency power only, but she will do about 23 knots at 4000 RPM, 100 KPA, WOT. For our boating style Hocus Pocus is over powered. Fuel economy is more important to us than speed is.

The original equipment engines are 351 Windsors, US marine conversion, rated 235 HP at 4200 RPM. They are quite rare in the ‘32’s as most of the gas option boats had 305 Chevs. The engines came with Holley 4160 carbs and electric chokes. The boat had relatively few hours on her when we bought her and the engines were in excellent condition. They started easily and ran well but they seemed to be running rich after start up and occasionally they would definitely over fuel until fully warmed up. I tore both carbs down, installed new “Renu” kits and made sure that all components were the ones spec’d for this application, but I still had the problems. I thought perhaps it was those crude electric chokes, so I built a pair of electronically operated chokes using a model aircraft servo motor. That helped a lot, but did not cure everything.

Holley is not my favorite manufacturer of anything. It’s a personal thing. Some people like them and have good success with them, but they are not known for good part throttle economy. If I have to have a carburetor my favorite is the Rochester Quadrajet. They are very versatile and can be configured to give very good part throttle economy and very good all out performance. A lot of people don’t like them because they are somewhat complicated and tricky to set up, but if you understand them they really are quite good. I toyed with the idea of getting a pair of them and spread bore manifolds, but ultimately rejected the idea because I would have to go through a lot of work and expense and still end up with a compromise situation.

The idea of converting to EFI kept poking away at my brain. I knew what would be involved and it would be a huge undertaking. Then double it because there are two engines, not just one. Programmable EFI in a motor vehicle is one thing, but in a boat it’s even harder because of the safety concerns. You have to make sure you do it right or the consequences can be disastrous.

I always had the feeling in the back of my mind that part throttle economy could be improved on somehow, but not with a 4160. Ignition timing also entered the picture. The distributors are your garden variety Prestolite mechanical advance only units. The advance mechanisms were in good condition. US marine spec’d the static timing at 6 degrees crank. Total timing at 3000 RPM was about 22 degrees. This seemed too conservative for me. Finally I couldn’t stand it any more and decided to install some test gear and find out just what the air fuel mix was at all points in the speed and load range. I installed a wide band O2 sensor and hooked up a spare Megasquirt so I could data log RPM, manifold pressure and A/F ratio. As I suspected, the A/F ratio was a lot richer than I wanted from idle up to about 2800 RPM. From then on it actually got quite good until the power valve opened up when it became overly rich again. I analyzed the data logs and reasoned that if I could optimize my A/f ratio and ignition timing, in theory I should be able to realize about a 25% improvement in fuel economy at and below about 2000 RPM. I would have been happy to see a 10% improvement.

I agonized over the decision. To convert or not to convert? I made measurements. I thought of all the things that could go wrong. I gave myself a few good slaps on the face, but in the end, I couldn’t resist the temptation and committed to the project.

I decided to do one engine at a time for two reasons. First of all, it would give me an ideal opportunity to compare numbers on the same engines, operating under the exact same conditions, with no difference other than the engine management systems. The other thing was that if I was terribly wrong, and things went sideway, I’d only have one engine to convert back, perhaps after a major overhaul.

Two years ago I did the Stbd engine and we ran the 2011 season with one engine stock, the other on EFI. After I got the tuning dialed in to where I thought it was pretty good we kept accurate fueling records. Cruising at 2000 RPM the Stbd engine got about 20% better economy than the Port. At 1900 it was about 22%, at 1700 it was close to 25%. There was no measurable difference in all out performance. Last fall I did the Port engine and we ran the boat about 45 hrs with both engines on EFI. We had no break downs or nasty surprises, but the tuning never seems to end. I’m always thinking I can improve on things a bit, but that’s really the fun part.

I’m sorry that this post got so long, but I’m not sure how I could have condensed it and still convey what I did and why I did it. If anyone would like details on exactly what I did to do the conversion just fire away, I’d be happy to share.      

Holy crap, Bob.
To be able to program your own fuel and spark curves by reading up about it is impressive. Yes, you had some help from a programmer but still, my hat's off to you.

How did you plumb the O2 sensor into the wet exhaust?

Hi KR,
Thanks for your kind words. Yup, that's the critter in it's relatively stock form. Ours has a hard top extension over the after deck. I'll put together a few photos in a separate post.

This site has more information about the EFI 351s than any other I have found. I stand to be corrected on this, but it is my understanding that they were produced only for a short time as a result of some kind of partnership between Volvo and OMC. I wasn't aware of the PCM connection. I also believe that the fuel injection set up was from the 5.8L F150 Lightning engines. They were relatively rare in themselves. The upper and lower manifolds have a much lower profile than the ones used in the trucks, which is important in a crowded engine bay. Finding these manifolds is next to impossible. The controller is just a standard OBDI EEC-IV with open loop tuning parameters specifically for the marine application. There has been some success in hacking these controllers, especially in the 5L Mustangs, but there is very little support for the older truck engines and I'm almost positive none for the marine.

No doubt I did my conversion the hard way with custom hardware and code, but my logic was that if I’m going to do it I’m going to do it in the best and most thorough way that I can.

For my conversion I just went to the local wrecking yard and bought the upper and lower manifolds, throttle body, rails and injectors, TFI distributor and remote TFI module and E-core coil. I ended up not using the distributor because I was concerned about it not being ignition protected, more on that later. The EFI manifolds are quite tall, and things are, shall we say, somewhat cozy in my engine room. I made many careful measurements, and cross checked them many times. I even made up a mock up of the manifold position to cross check my clearances. There is no way they would fit with the throttle body forward, but I figured if I chopped it off and moved it to the back side I could fit it in. I calculated I'd have about 5mm clearance from the top of the manifold to the deck head, and an interference of about 2 mm to the right side exhaust hose. I got around the interference by notching the plenum and making an indent for the hose.

I use a fuel return to tank system with an accumulator. A solid state low pressure pump draws fuel from one of two tanks for each engine. The low pressure pump outputs to the accumulator and back to tank. A high pressure pump draws from the accumulator, outputs to the fuel rails and returns to accumulator and tank. The TFI ignition expects a square wave at system voltage signal every time a cylinder comes up on compression at 10 degrees BTDC. Megasquirt takes this signal and does the calculations for spark timing for the next cylinder in the firing rotation. It doesn’t know or care which cylinder it is as the distributor takes care of these duties. Because I had concerns about the non marine TFI distributor I elected to keep the original Prestolite but just use it for spark distribution, not ignition pick up. I got my ignition pick up by mounting 8 rare earth magnets with alternating polarity, 45 degrees apart, on the harmonic balancer. I use a latching hall effect sensor to produce the initial signal and a simple conditioning circuit to output to Megasquirt. This is similar to the method Simple Digital Systems use on their EFI set ups, except that they don’t use a latching sensor.

The fuel pumps and accumulator are mounted on the back of the engine and the E-core coil is mounted near the distributor. The TFI module, relay board and auxiliary board are mounted remotely in the engine room and the ECUs are mounted in the master stateroom just forward of the engine room. The left bank riser houses the wide band O2 sensor and exhaust gas temperature thermocouple. I run open loop only so the O2 sensor is just there as a tuning aid and a sanity check. I have a knock sensor as well, but it is just a tuning aid and sanity check with no active feed back.

I built a small “digital dash” so I can monitor all of the engine parameters real time without connecting to a lap top. I also have potentiometers for real time fuel and ignition trim. If I want to make any permanent tuning changes I do it by connecting to a lap top and running the Tuner Studio software.

I have high resolution transducers for lube oil and fuel pressures with alarms for low oil pressure, low or high fuel pressure , high coolant temperature, high exhaust gas temperature and a rev limiter. I calculate and display fuel burn in Litres per hour from accumulated injector on time and have it dialed in now so that I am within 3% accuracy or better. I also have a totalizer for fuel burn so I can see how much fuel I’ve burned since last fuel up and reset.

Like I mentioned, it was a huge project, and it’s never really over, but that’s what I do for fun.

I haven't heard of the Megasquirt. I'll have to do some research.

Problem with most of these plug and play EFI systems is:
1) Numerous automotive kits have been very successful transformations. Marine applications are pretty much non-existent as far as I know.

2) The programming of the fuel and spark curves is a magical cloud that would make Walt Disney turn over in his grave and is reserved for engineering geeks who can spell Holley but have no idea how to change a jet or why. They can make a PC sing like a concert pianist playing Beethoven's 5th though.

It's a rare bird that can do both. Congrats on making that transformation. I'm envious and would love to have that skill set.

Here's a few shots of the boat and EFi installation.

This was very interesting. I can see why some would want this,my 91 5.0 Mustang started easier than anything I have ever owned.

wow great thread. An engine nerds delight!! Great work.

AlfaDon wrote: Will a well adjusted carb do well in this situation?

Yes it will. The problem you have is that sometimes trying to find a good carb tuner can be a challenge in itself. Many say they can do it but few are really good. Another option is buying a book, reading and learning something. Then do it yourself. There is some very good literature out there to do just that. Look at what Bob learned by doing that. I would take an educated guess that most everybody on this site that has the expertise that they have is by doing that and then going through a lot of trial and error testing on their own.

Carbs are a mysterious area that many feel intimidated by but if you take some time to dial one in, they can be extremely reliable, efficient and accurate. Carefully tuning one can be done for well under $100 in parts, some patience and most of all, some knowledge.

Most people have become so spoiled by the EFI in their everyday cars and trucks that they think it's the Holy Grail and it magically will fix all their problems.
I'm with Hollywood on this one. I'll stick with my carb. It runs perfectly fine. I don't need or want EFI but this is very interesting stuff.
Besides, a carb sitting on top of a motor is just plain bad ass. These modern EFI monstrosities don't even resemble a motor anymore.

E4ODnut wrote: Megasquirt handles altitude compensation in one of two ways, fixed correction or constant correction. Fixed is when the ECU first powers up it takes a sample from the MAP sensor which will read atmospheric. It stores this number as barometric pressure in memory and uses it along with a compensation table to adjust for altitude. This works fine if you are not in the mountains and going through extreme altitude changes. It can be made to work well, but you just have to pull over from time to time and do a restart to get an updated barometer reading.

My guess is that you'd have to go through a number of locks (or over a good sized waterfall) for this to be an issue on a boat.

I skimmed the megasquirt page... seems like a neat set up. Which flavor are you using? It sounds like most of the modules can control both TBI and multiport set ups?

E4ODnut wrote: Because I had concerns about the non marine TFI distributor I elected to keep the original Prestolite but just use it for spark distribution, not ignition pick up. I got my ignition pick up by mounting 8 rare earth magnets with alternating polarity, 45 degrees apart, on the harmonic balancer. I use a latching hall effect sensor to produce the initial signal and a simple conditioning circuit to output to Megasquirt. This is similar to the method Simple Digital Systems use on their EFI set ups, except that they don’t use a latching sensor.

Can you give us a bit more info on how your ignition system is set up? Fuel is pretty straightforward. I cant see how you would bypass the mechanical advance in the Prestolite if youre still using it to distribute spark... and being able to control your advance curve would seemingly be one big advantage to a custom tune.

Thanks for sharing, by the way- cool stuff!

Don't forget Chris a boats engine is working hard all the time.A smaller engine might have to have more throttle and then use more fuel.
In a case like Roberts a repower with diesels would be the norm to save fuel but the most expensive route too.

Great info Robert. I was going to wait for JoeinNY to start fiddling with the GT40 engine in his 95 SN project. I am pretty sure he will not be able to resist putting a stroker kit into that engine which would require this type of solution.

I have plans to freshen up the GT40 in my 98 Sport but have been waiting for Joe to do all the hard work on a stroker conversion for the EECIV controlled engine. Interesting that they produce a compatible loom. Looks as though all the hard work has been done. Anyway Joe keeps collecting too many projects anyway. May have been at least a couple of years before that damn Joe got back to that 95SN project anyway.