EFI Conversion

[tomelenbaas]

I asked this question last year and did not get any feedback, so I'll ask it again.

I'm thinking of doing a throttle body EFI conversion on my 1988 Mariah (PCM 351W Ford engine). There are a number of kits out there, including Holley's Pro-jection and Avenger systems; FAST; Affordable Fuel Injection; and Howell. I'm leaning towards the Howell kit because it seems to be one of the easiest installs (as well as one of the most affordable). It looks like the most difficult part of the install will be having the exhaust manifold machined for the O2 sensor and running the fuel return line. The Pro-jection and Affordable kits do not require an O2 sensor, but it seems like the O2 sensor is essential to get the full benefit of a fuel injection system.

Does anybody on the forum have any experience with EFI conversions - good or bad? If so, which systems? I have spoken with one person who put a Holley Pro-jection system on a 1990 Mastercraft and loved it, but I'd like to have a larger sampling for my survey.

Thanks.

[rludtke]

I too have thought about this, but eventually abanded the idea when I finally ironed out my carb problems (it is decidedly cheaper to live with the carb). What I learned is that the o2 sensor is really a smog improvement element, that helps finess the system, but it is not necisary for the system to work well. Considering that we have water in our exhuast, I don't even know if a normal automotive o2 sensor could live in the environment. So I think you could live just fine without it.

EFI is great from the users perspective, you just turn the key. But, I have been able to dial my carburator so that it becomes just as reliable and pain-free. From a distance, I wouldn't be able to tell the difference.

[riveredge]

While I can't speak to the conversion specifically, I think Rick said it well, the main benefit is ease of use, anyone can just get in and turn the key, which is nice. I replaced the engine in my 89 with a newer EFI engine, and really it's not much different. The biggest difference is power, but that's because the new motor was a GT40. I wouldn't have done it if I had to pay full price for the motor, or for the labor. That being said, there's really no downside if you're doing the work yourself, and you have the money to spend.

I also don't think you need an 02 sensor, most EFI boats don't have them. As long as the computer doesn't need a reading to function, you don't need it. I would ask over on the Correct Craft Fan forum, too, because the engines are all the same in the 80's Supras & Nautiques, and there are more Nautiques out there so someone is bound to have done this.

Good luck, and let us know what you decide!

[wotan2525]

I looked into it and basically decided there wasn't any benefit. Sure, they start easier but is that worth $1500? You can pay an expert a LOT of money in carb adjustments before you get there.

[cadunkle]

I'll start by saying I hate fuel injection. It's complex and prone to leave you with a non-running engine for any number of reasons when everything is mechanically sound. I owned a fuel injected vehicle once, and it was the only vehicle I ever owned that I had to pour gas down the intake to get it to start in cold weather. Threw a lot of time and money at that trying to fix it to no avail. I don't own any fuel injected vehicles and never will, I don't trust them. I won't depend on one to get me to work every day and I certainly won't have one in my boat where a stalled engine could put me in the middle of a shipping channel where I could get killed by anything from barges to tankers to aircraft carriers. Remember that DUKW tour boat that got run over by a ship? Yeah, that's where I boat. I value my life and the lives of my friends too much to risk it. I flat out do not trust fuel injection or any complex and fancy electronics.

That being said, if you really want to do EFI don't do TBI. There is absolutely no benefit to TBI over a carb. You get the same fuel distribution issues and such as a carb has. You have a 351w, so convert to an off the shelf marine or automotive fuel injection system that came on these engines if you must have EFI. As far as I know, Ford never did TBI on their V8 engines, nor did any marinization company.

Perhaps a better question would be what are you hoping to gain from fuel injection? A carb will deliver just about everything an MPI system will and is far cheaper and easier to tune if your motor is anything aside from bone stock. Even MPI isn't the end all be all of fuel distribution and individual cylinder tuning, webers will get you the same thing, though can be more expensive than EFI and kind of ridiculous for a tow boat.

[tomelenbaas]

Thanks to those who have shared their views.

My only reason for considering fuel injection is to deal with altitude issues. For the first 20 years that I owned my boat every place I used it was between sea level and 2,000 feet. As a result I never had any issues with carb performance. But I'm now regularly going to a higher elevation lake (about 5,000 ft.) and at that elevation my boat is a dog out of the hole. Once I'm on plane it's fine, but getting there is a whole other story. My understanding (and maybe it's a misunderstanding) is that carbs have to be rejetted for higher elevations but that a good fuel injection system will compensate for the thin air. I'm not looking for any radical boost in power or fuel economy - all I'm looking for is an easy way to deal with changes in elevation without having to constantly rejet a carb as I go between lakes.

I'm certainly open to (and greatly appreciative of) alternative suggestions to address this issue. Thanks.

[rludtke]

Yes you would have to decrease the size of your jets to accomidate the thinner atmoshere, but the jets simply thread into the metering block, and cost less than $5 for the whole carb.

Holley's gaskets can handle multiple tear-downs of the float assemblies and metering blocks, which is great for tuning and testing. However, if your carb has not been taken apart recently, than the gaskets will likely tear upon taking them apart. Because of this, I recomend purchasing an overhaul kit, as it comes with all of the gaskets, and while your at it, throw in the rest of the replacement parts from the overhaul kit. The kit doesn't have the jets, but they are easily ordered. There are lots of carb parts suppliers on E Bay Stores. I have found overhaul kits on E Bay Stores for as low as $25. The links below should be helpful:

Holley 4160 carburator: http://holley.com/0-80319-1.asp
overhaul kit: http://holley.com/703-47.asp
Holley technical library: http://holley.com/TechService/Library.asp
4160 exploded view: http://holley.com/data/TechService/Technical/4150%204160%20Exploded%20View.pdf
Float adjustment procedure for the 4160 (follow the Duracon (plastic) procedure): http://holley.com/data/TechService/Technical/4150%204160%20Exploded%20View.pdf

The float bowl retaining bolts will also allow the fuel bowl to drain. Remove one of the lower bolts, and hold an empty container such as a water bottle to capture the stream, to keep it out of the bilge (stuff a couple of paper towels under the bowl as well). After draining, the bowl can be removed in a minute. Once removed, the jets are exposed, and they are threaded out with a screw driver. Screw in the replacement jets, remount the float bowl, and the engine is ready to start. You could re-jet your carb in less than 10 minutes in the boat (and even on the water). If this is something you will do fairly often, then order up some replacement gaskets for the bowl, and the bolts, and keep them in your boat just in case one fails and can't be reused. The gaskets are probably less than $5.

You could do this operation 1000s times or more and still not reach the cost of an aftermarket EFI system because the jets are a re-usable one time purchase, and the gaskets are highly re-usable. Yeah, I know, it's a pain, but I wouldn't hesitate to swap jets back and forth if it where me.

If you have any questions specific to working on your carb, don't hesitate to ask. Save your money for fuel!

[tomelenbaas]

Thanks, Rick. I've always thought of carbs as complicated beasts - still do, but you make the replacement of the jets seem like a relatively simple and inexpensive task. I think I'll give that a try first.

[cadunkle]

Buy two of these and you're golden for quick and easy adjustments. Just get it set for where you normally boat and then figure how much to turn the screw to get the ideal mixture for your higher elevation. I wouldn't want to be changing jets every trip out, it would get annoying.

http://www.summitracing.com/parts/PHP-15005/

If you have a 4160 you're SOL, swapping metering plates would get REALLY old. They do make metering plates that accept standard jets, and the kits come with slimmer floats to clear the jets. They are not externally adjustable though, so if you have a 4160 I'd just convert to a 4150 and run the Percy's adjustable jet plate.

[tomelenbaas]

The Adjust-a-jet sounds like a perfect solution for my situation. In looking at the Percy's and Jegs websites, the model 15001 will even work on a 4160 with the 15008 extension cross-over tube. Thanks for bringing this to my attention.