Converting to carburetor from mpi 350 mag

Ignatios

Petty Officer 3rd Class
Joined
Mar 15, 2015
Messages
88
Hello All,
Ok short and sweet:
I have a Larson Cabrio 330 year 2000
Engines are 350 mag mpi vortec serial number L365398
Struck by a lightening fried both ECMs
Sent over to test them the tech said they’re fried you can’t refurbish them, he has a refurbished ones each for $2500 plus tax plus shipping plus labor and I’m sure the bill will go way beyond that…ouch
So I’m considering converting to carburetors.
Please any advise/info on a kit to convert them where do I go to or order them from online sites what should I buy or look for or cheaper mefi 3 your thoughts/advise is well appreciated, God bless.
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
10,895
Edelbrock has Marine Manifolds for the SB Chevy
Holley has several Carbs that will work. My preference is the 650 Spreadbore.
I don't know if the Ignition Advance is provided by the ECMs which are fried, or is Independent. You might have to get a Distributor that has it's own advance.
 

Fun Times

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Scott06

Captain
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Messages
3,695
Hello All,
Ok short and sweet:
I have a Larson Cabrio 330 year 2000
Engines are 350 mag mpi vortec serial number L365398
Struck by a lightening fried both ECMs
Sent over to test them the tech said they’re fried you can’t refurbish them, he has a refurbished ones each for $2500 plus tax plus shipping plus labor and I’m sure the bill will go way beyond that…ouch
So I’m considering converting to carburetors.
Please any advise/info on a kit to convert them where do I go to or order them from online sites what should I buy or look for or cheaper mefi 3 your thoughts/advise is well appreciated, God bless.
In addition to manifolds, carbs, throttle brackets, fuel pump & lines, I suspect you will need a carbed wiring harness and ignition system like TB V or delco est. This may make the ecu replacement look less expensive than it feels now…

i assume lightning strikes arent covered by insurance?

these guy are often mentioned for ecu rebuilds

 

QBhoy

Admiral
Joined
Mar 10, 2016
Messages
6,597
Jeez. Never heard of that happening. What was the circumstances and details, out of interest? Where was the boat etc ? Marina ? Was it running when it happened? You’d think earthing would avoid this.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
10,024
do you have this intake manifold? I think then you'd need a new 4 bbl intake for both engines, you can use a spread bore cast iron intake or aluminum square bore as long as its a marine unit, that gives you a choice of any 4bbl marine carb that will meet the needs of the engine (Edelbrock or Holley), I'd say 600 or 650 cfm. However, you have to deal with other aspects of the fuel system, you will only need a low pressure electric pump, this must have a safety harness wired into an oil pressure switch to turn the pump off when the engine is not running. That and you have to figure out how spark advance is handled. While it is possible there are numerous points that have to be thought through and dealt with:
distributor
fuel pump
fuel lines
intake manifold
carb throttle linkage
carb electric choke wiring
by the time you're done it might not be cheaper than replacing or repairing (if possible) the ecms
a new carb is anywhere from approx 500-800 depending on the model, intakes start at 300 & go over 400, then you have to add whatever electric pump set up you are going to use, work out the wiring details and distributor, etc.
 

poconojoe

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Messages
1,903
Jeez. Never heard of that happening. What was the circumstances and details, out of interest? Where was the boat etc ? Marina ? Was it running when it happened? You’d think earthing would avoid this.
I feel for the OP.
Not boat related, but I had a bunch of electronics fried in my house once.
It cost me a big chunk of money.
I now have a whole house lightning arrestor connected to my circuit breaker panel.

I was at my kitchen window and I saw a lightning strike in my neighbor's backyard and a really loud thunder crack. I never heard such a loud thunder crack.

Some breakers were tripped in my panel. It blew out resistors in my alarm panel, fried (wired) alarm window contacts, my oil burner multi zone control panel, a UPS for my computer, a printer, various power supplies, a roku stick, my garage door opener, my security camera system, one of the components for the cable tv.
 

QBhoy

Admiral
Joined
Mar 10, 2016
Messages
6,597
I feel for the OP.
Not boat related, but I had a bunch of electronics fried in my house once.
It cost me a big chunk of money.
I now have a whole house lightning arrestor connected to my circuit breaker panel.

I was at my kitchen window and I saw a lightning strike in my neighbor's backyard and a really loud thunder crack. I never heard such a loud thunder crack.

Some breakers were tripped in my panel. It blew out resistors in my alarm panel, fried (wired) alarm window contacts, my oil burner multi zone control panel, a UPS for my computer, a printer, various power supplies, a roku stick, my garage door opener, my security camera system, one of the components for the cable tv.
Terrible thing to happen.
 

tank1949

Lieutenant
Joined
Apr 4, 2013
Messages
1,455
Hello All,
Ok short and sweet:
I have a Larson Cabrio 330 year 2000
Engines are 350 mag mpi vortec serial number L365398
Struck by a lightening fried both ECMs
Sent over to test them the tech said they’re fried you can’t refurbish them, he has a refurbished ones each for $2500 plus tax plus shipping plus labor and I’m sure the bill will go way beyond that…ouch
So I’m considering converting to carburetors.
Please any advise/info on a kit to convert them where do I go to or order them from online sites what should I buy or look for or cheaper mefi 3 your thoughts/advise is well appreciated, God bless.
look in the web. Someone is always retrofitting to OBs.
 

Scott Danforth

Grumpy old guy who plays with boats
Joined
Jul 23, 2011
Messages
40,978
Two Edelbrock marine intakes, two Voyager distributors, two Edelbrock or Holley carbs and you are about $2200
 

Scott06

Captain
Joined
Apr 20, 2014
Messages
3,695
Two Edelbrock marine intakes, two Voyager distributors, two Edelbrock or Holley carbs and you are about $2200
I think those prices are pre insanity, he will be close to that per engine. These are off Michigan Motorz web page
eddelbrock 1409 $573
delco est $475
Cast iron intake $599 (Eddy intake is cheaper but OOS)
low pressure fuel pump $189
throttle bracket for carbs merc 805359T. $68
Flame arrestor $149
$2053 per engine doesnt include gaskets fuel lines wiring harness if needed…

if its $2500 per engine for new ecus thats probably a better bet except for the wallet.
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
10,024
If I were doing this (and I greatly prefer carbs for older boats, can’t be beat for cost of repair & maintenance) I’d be looking to sell off all the usable EFI stuff to defray the cost of conversion.
 

Ignatios

Petty Officer 3rd Class
Joined
Mar 15, 2015
Messages
88
You follows are awesome I just can’t believe the wealth of info you all provided me with I already made a phone call and this follow was so helpful I still want to research ball this info and make a decision I would rather go with the mefi even if I have to program it to my engine if the price make sense but this gentleman I talked to he said actually going with a carb I’ll gain about 30 horse power and less problem.
So I will let you know what I went with and how did the boat run.
Thank you so much again and God bless.
 

Scott06

Captain
Joined
Apr 20, 2014
Messages
3,695
You follows are awesome I just can’t believe the wealth of info you all provided me with I already made a phone call and this follow was so helpful I still want to research ball this info and make a decision I would rather go with the mefi even if I have to program it to my engine if the price make sense but this gentleman I talked to he said actually going with a carb I’ll gain about 30 horse power and less problem.
So I will let you know what I went with and how did the boat run.
Thank you so much again and God bless.
30 more hp with a carb? not sure that dog hunts… fuel injection is great until it doesn’t work…carb is great because you can fix it with a $50 rebuild kit and hand tools, but you will be working on it from time to time. In 20 years of ownership on my old boat i had to do two carb rebuilds and one choke element…
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
10,024
Exactly
If you know carbs you can keep the boat going for a LONG time for little money. EFI is nice for for cold starts & smooth running when cold other than that I don’t think the huge cost penalty of EFI is worth it.
Don’t think that changing to a carb will add power.
Best thing about carbs? Parts are very well supported in the aftermarket. Not like Merc & VP making various EFI parts NLA. I can get everything for a Quadrajet that hasn’t been built in 30 years! Holley & Edelbrock parts are everywhere.
 

Scott06

Captain
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Apr 20, 2014
Messages
3,695
Exactly
If you know carbs you can keep the boat going for a LONG time for little money. EFI is nice for for cold starts & smooth running when cold other than that I don’t think the huge cost penalty of EFI is worth it.
Don’t think that changing to a carb will add power.
Best thing about carbs? Parts are very well supported in the aftermarket. Not like Merc & VP making various EFI parts NLA. I can get everything for a Quadrajet that hasn’t been built in 30 years! Holley & Edelbrock parts are everywhere.
Yeah thats what keeps us going, but for some folks carb rebuild is beyond their skills. Worst case with a carb replace it for $500 with a new one …

i would be worried about doing business with the guy who said carb will make 30 more hp …
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
10,895
If the Engine is putting out 300 hp with EFI, swapping to a Carb is not going to give much more. If it is putting out 260hp, then the potential for close to 30 more hp is there.
 

Scott Danforth

Grumpy old guy who plays with boats
Joined
Jul 23, 2011
Messages
40,978
carb wont get you 30hp by itself. however with a carb spacer, you can increase plenum volume and get a bit more in the mid-range.

A rocker change to 1.6:1 rockers will net you some hp as well

350 Mags were rated at 300hp (prop). that is 320hp at the crank. you can get the same power with a carb

while it is possible to get a lot of hp out of a carbureted SBC. you wont be doing it with wet exhaust.
 

Ignatios

Petty Officer 3rd Class
Joined
Mar 15, 2015
Messages
88
Ok guys after going back and forth and talking to few pros. Even one who is in the ECM business it seemed the most agree that to this … if you’re having problem with your ECM, EFI etc it is cheaper to go with the carb, the gain is far less headaches far easier and cheaper to fix and potential to gain few horse power… one of pros told me that NESCAR when they had to switch to ECM or EFI. They weren’t pleased they lost 100 hp and after long struggle they barely gained it back the down side is that the carb you have to warm the engine up before taking off you lose efficiency on fuel and boat value in case you’re selling … if the ECM is fixable and you’re not having much problems is better to keep it.
So in my situation it made more sense to switch to carb especially since they don’t make the ECM 16236999 MEFI3 anymore much cheaper far less headaches I can maintain it myself without any special tools and digital gadgets.
I’m going with 800cfm carb I was told this might be a little too much if I’m running low RPM but I will gain up to 60 hp pet engine if I everything is set right.
Your thoughts is well appreciated
Thank you very much.
 
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