1991 American Boat, 5.7 Mercruiser Convert to EFI

[Johnsonizer]

Hi,
New to the forum and have been doing some research on converting my carburetor to EFI. The motor was rebuilt 5 years ago, has 200 hours on it, runs very well. It is hard to start when warm and noticed a performance decrease on last outing.
Was thinking to get it in for a tune up but before I spend the money on that was wondering if its possible to upgrade to EFI, might eliminate the hard starting and improve fuel economy too. Also hopefully would improve the performance a little since it seems to be dropping off, and instead of doing the carb over the conversion would eliminate some unreliability of the carb (although a trade off I guess).
Some research on the internet shows there are kits from Holley but I was hoping to find someone who actually did a similar engine. On EFISystemPro.com they talk about marine conversions but there are issues with pumps and exhaust o2 sensor, obviously would be a problem. GoneOutdoors has an article about doing the conversion with a kit with no mention of o2 sensor.
Thoughts from anyone on here with experience.
Appreciate any feedback.
Brad

 

[alldodge]

You can go EFI but make sure which ever system you get that it is Marine (USCG Certified)
Holley Sniper EFI cost around $1K

 

[Bondo]

Ayuh,..... Welcome Aboard,........ Is it a 2bbl. or 4bbl. carb,..??

Efi will never pay for itself,..... even doin' All of the work yerself,......

A 4bbl. carb can do everything Efi does,....... power, 'n economy wise,.....

1991 woulda been the tail end of the Quadrajet carbs, just before Merc went to their AFB carbs they still use,....

The AFB carbs are carbon copies of the Edlebrock 1409,.....

 

[Johnsonizer]

I will check tonight the carb. I was hoping for less maintenance with the EFI setup. Not concerned about paying it off through savings or getting more power. Just want to get the power consistently and better starting.
Had it out on Saturday and had 2 people in the boat and 2 people in a tube and it could not achieve plane. And if you go all the way full throttle lost a bit of power. Had to have the person in boat move to the front to get up on plane. People in the tube were large

 

[Scott Danforth]

define hard to start when warm

no such thing as less maintenance on a boat. you either clean a carb every 5-10 years from crud in your fuel or you pull injectors and send out for cleaning every 5-10 years from crud in your fuel. and that is assuming you buy good fuel and replace the filters every year.

your loss of power may be fuel system related. it may be fuel quality related, it may be loss of compression

what is your fuel pressure? what is your compression?

 

[jesse_boston]

On mine, I sometimes need to open the throttle a couple times before starting when cold, and when warm I have to bring it up to 5%-20% throttle while cranking, and it takes 10-20 seconds of cranking before it'll kick over.

I'd say this is "hard starting when warm"... is this something that should be easier?
It'd be nice if I could have my other family members be able to start up the boat when loading or unloading from the trailer, or for example if I need to stay on shore to fix the trailer.

I've also been thinking about how nice the (ford) EFI boat was that we sea tested.