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EFI system swap

Donski

New member
I'm looking to convert a 351W in a 96 Ski Nautique over to EFI, and I'm wondering how much I can scavenge from the automotive world. I know that the EFI systems from the fox body mustangs (87-93) are a direct swap except for the lower manifold. What components need to be marine specific? I understand that the starter, alternator, distributor and intake need to be flame proof. Is there anything else? What about the power curve in the EEC? How does that differ from the automotive world? Is there a way to flash the EEC for a different curve, or should I go with a different ignition system or EEC? I've thought about Mega-squirt, but that's a whole 'nother learning curve.

Thanks,
Don
 
I'm not the one to be asking about the EEC interface, etc., other than to suggest that ignition curve will be substantially different from that of the automotive curve. To get a rough idea, take a look at a few of the Mercruiser MPI or TBI ignition advance curve graphs, and compare these to a few of the HP Automotive EFI ignition curve graphs. You'll see quite a difference.
Detonation can be the Marine Gasser's worst enemy if the curve does not suit the Marine Engine loads.

Also, certain aspects of the Automotive EFI system may not meet USCG regs. This could get you a citation, and if you were to have a mojor issue, your Marine Insurance policy will likely not include such coverage.

This day and age, it's silly to operate a vessel without proper insurance, IMO.

On the other hand, I love thinking outside of the box. Just be careful.

.
 
Last edited:
Donski

Sorry I was a bit slow getting back to you I had to go looking

Having both worked on a OMC 351 EFI system and adapded a street system to a marine 351 the major diferance I found was the fuel delivery on the marien system dose not have a return to the tank. Also all the fuel lines are stainless after the fuel pump.


I spent a lot of time trying to determain just how the power curve difered from the automotive system and the OMC set up and was not able to find anything specific. What I did find was total advance data to rpm. With EFI this curve is controled by RPM/manifold vacuum/ and the knock sencer.
Basicly the controler figures it out and ajusts timing and mixture to the load. It dosn't mater if its in a truck a car or a boat.

Trust me I was very hesatent to make the invesment of time and $ and all your concerns regarding marine verse street and there are a few i.e. the fuel delivery. Like Rick points out safty is formost. As to the control system its a lot more giving than you think.


Nixes mate
 
Having both worked on a OMC 351 EFI system and adapded a street system to a marine 351 the major diferance I found was the fuel delivery on the marien system dose not have a return to the tank. Also all the fuel lines are stainless after the fuel pump.
I believe that the fuel return line is one of the issues here. I'd think that the pressure lines could be dealt with.

I spent a lot of time trying to determain just how the power curve difered from the automotive system and the OMC set up and was not able to find anything specific.
You should be able to find the curves if you look deeply enough.
Just do a generic ingition advance curve graph search. I've seen these quite often when searching for Marine curves, but have never paid any attention to them.

What I did find was total advance data to rpm. With EFI this curve is controled by RPM/manifold vacuum/ and the knock sencer.
Basicly the controler figures it out and ajusts timing and mixture to the load. It dosn't mater if its in a truck a car or a boat.
Again, I think that if you were to compare the two, you'd see quite a difference.
It's all about LPCP and how we get there, yet avoiding Marine Load Detonation potential with the Marine Engine ignition advance.

HP automotive engines typically pass through the RPM range where Detonation potential may be greatest, whereas with Marine Loads in a cruiser style boat, we tend to remain at/near these RPM ranges for sustained periods.
Detonation can be self perpetuating. A cylinder detonates, and the cylinder temperature increases. As cylinder temperatures increases, detonation becomes exaggerated, and it self perpetuates, and so on.

As you know, the damage can be anywhere from mild to ugly..... and it can cause severe damage in a split second given the right conditions.

The ECU, EEC, or whatever controller is used, along with knock sensor influence, etc, apparently does cut back advance when needed. However, (and I don't know the answer to this myself) how many samplings will the controller require before establishing a consistent advance curve and correct fuel metering?

Trust me I was very hesatent to make the invesment of time and $ and all your concerns regarding marine verse street and there are a few i.e. the fuel delivery. Like Rick points out safty is formost. As to the control system its a lot more giving than you think.
Well, my point went a bit furture than just safety alone. Engine safety would be included, IMO.

Nixes mate

Like said, my knowledge is limited in this area. If you can make this work safely, my hat's off to you.

Good topic, and I'd sure love to have both of my engines equipped with fuel injection.
One issue for me is, I'm not a fan of EST systems. Most good FI systems require an EST ignition system.
Call me "old school" if you want to. :D
 
Thanks Rick

Not to get overly analitic, what I am saying is that the controler via the MAP/Knock/Temp ect. createts the corect power curve requiered for the given conditions. I can say this with confidence because of the 80+ hour season I just had. I was also very pleased with my fuel economy compared to the my previous season using the carb.

Have a Great Thanksgiving

Nixes mate
 
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