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1988 Formula 350/320HP EFI Conversion

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OldMagicfloat

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Discussion starter · #1 ·
Hello all,
Hope someone can help with this. I have a 1988 Formula 206LS that has an uncommon 350/320HP (Bravo 1 OD) EFI from Mercury Racing. I have had an occasional flooding problem. The engine fires up instantly every time, but once in a while I smell fuel richness at the dock then the motor floods and shuts down. Other times it runs just fine and can't make the problem occur. Parts availability for the EFI is a BIG problem, along with lack of documentation and skilled mechanics.

I have just pulled the EFI and the manifold off am going to replace the intake and put in a carb. I have been told that a Holley 600CFM is the best option. I don't want to lose a lot of performance. Does anyone have any insight on carb size for this set up? THANKS!
 
#2 ·
You'll need a 87-95 'late model' style intake manifold. Let me know if you need help here and if you want aluminum (fresh water only) or cast iron.

600 is perfectly fine.

I just installed a BG 650 Vac sec carb on my 5.7 and absolutely love it. They are pricey - mid $500's - but are better made and come with 4 corner idle, rear metering blocks that have replaceable jets, and quick change secondary spring cover, which don't come on your standard marine 600 Holley vac secondary.

You'll also need to mount a mechanical fuel pump or atleast different elctric pump with carb ready fuel psi.
 
Discussion starter · #5 ·
Thanks CFM, Appreciate your input. I am probably going with the cast iron manifold. The boat is currently in fresh water, but want the flexibility to use it on the bay/ocean. The Holley is on order so I will probably stick with it @ around $350. I am aware of the fuel pump change required to support the carb installation.

I am giving up anything by going this route? I did not really want to dump the EFI as it was a cool set up, but the lack of anyone that could diagnose/fix problems with it pointed me to a carb solution.

Thanks again...
 
Discussion starter · #6 ·
1BAD16,
I probably will have no use for it, but as you know from my post the ECM has a problem that several mechanics have tried to resolve to no avail. Also, the manifold was showing a lot of corrosion. I will let you know about the EFI once I take a closer to end of job on this project.
 
#8 ·
skier50 said:
I am probably going with the cast iron manifold. The boat is currently in fresh water, but want the flexibility to use it on the bay/ocean.
Click to expand...
I would strongly suggest the Bowtie Cast Iron intake for late model heads. The regular cast iron intakes will choke the motor you have....big time.


Image
 
Discussion starter · #13 ·
Hey Cuda,
Thanks much.. Sounds like you have a good set up now. That EFI has been nothing but headaches so it is history. Looks like it really caused you a BIG headache for sure.

Appreciate the facts on the engine, as I knew it was well built, but did not have any details. Anything else you can tell me? I have not been able to find any details.. Thanks!
 
#14 ·
World products has aluminum intakes with brass water passages for marine use. They work great. Just another option.

The Holley is a marine carb correct? If not the finish that Holley puts on the std car carbs will oxidize rapidly. Also you need the marine carb changes to be safe in case of any problems. Losing a life over a few hundred $$$ is not worth it.
 
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skier50
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