Converting EFI to Carb 4.3 Mercruiser

get-r-done

Cadet
Joined
Sep 15, 2008
Messages
15
What would be involved and necessary to convert an EFI TBI setup to Carb? This is a 2000 Model year engine. The new ECM conversion kit is just too costly to purchase. Considering converting to Carb to avoid the 3500.00 expense.
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Converting EFI to Carb 4.3 Mercruiser

What would be involved and necessary to convert an EFI TBI setup to Carb? This is a 2000 Model year engine. The new ECM conversion kit is just too costly to purchase. Considering converting to Carb to avoid the 3500.00 expense.

What is the problem with the old system?? There a little eaiser to repair than you might think.
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: Converting EFI to Carb 4.3 Mercruiser

:D Ive been there..It seems to me your dropping a efi motor into a boat that is not wired for it..duh.. so take off the intake ..pull off all the wiring and get that pigtail i posted in the other thread opps and probably a new elect fuel pump

Your going to have to rewire the motor there are no patchwork..work arounds..Its seems like a big job but its not as long as either you or mech has a full understanding of the wiring and what he needs to do.

1. new fuel pump your 4.3 does not have provisons for a mech pump
http://www.ecrater.com/product.php?pid=4057198

2. There's the plug it should plug right into your old boat
http://www.cpperformance.com/detail.aspx?ID=838

3. One good person who knows wiring its not that tough if you know where your going
 

get-r-done

Cadet
Joined
Sep 15, 2008
Messages
15
Re: Converting EFI to Carb 4.3 Mercruiser

What is the problem with the old system?? There a little eaiser to repair than you might think.

The problem is that there is an option set for "load anticipation mode" According to the mechanic he believes this is leaving the engine at base time mode all the time. He is claiming that at any throttle position, the timing will not advance. It sounds to me that the signal is expecting a ground to work properly. If I am missing something from a previous post my apoligies, but I don't see anything from old wiring that would change this setting if it truly is the problem. Don by all means jump in there and and explain.

Thanks

MIE Inboards Only
Load Anticipation Mode:
The Load Anticipation mode is on MIE inboard and ski engines only. The function is used to help inboard engines during shifting. An electrical signal from the neutral safety switch (on the transmission) goes to the ECM on J2-20. This signal tells the ECM if the switch is closed or open. In neutral gear, the neutral safety switch is closed (signal grounded). When shifting into gear, the switch opens (signal open). When the transmission is shifted into gear, the open signal causes the ECM to add a calibrated amount of bypass air with the IAC. This is done to increase the load handling capability
of the engine when going into gear on larger boats. When shifting back into neutral gear, the additional IAC bypass air is removed in an attempt to limit engine rpm flares. The amount of IAC air used is constantly monitored by the ECM. After the transmission is shifted, and the engine has stabilized, the ECM calculates an ?error band? from the Moving Desired RPM mode and adjusts the Load Anticipation mode IAC count accordingly. This allows the ECM to ?learn? the best IAC bypass air position to use for shifting each particular boat. NOTE: The Load Anticipation mode is on MIE 454/502 cid inboard engines also.
 
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